Cisco IOS IP Routing: BGP Command Reference
BGP Commands: M through N
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BGP Commands: M through N

Contents

BGP Commands: M through N

match additional-paths advertise-set

To match on paths that are marked (tagged) with a specific path-marking policy, use the match additional-paths advertise-set command in route-map configuration mode. To remove the match additional-paths advertise-set command from the configuration file, use the no form of this command.

match additional-paths advertise-set [ best number ] [ best-range range-start range-end ] [group-best] [all]

no match additional-paths advertise-set [ best number ] [ best-range range-start range-end ] [group-best] [all]

Syntax Description

best number

(Optional) Matches on paths that are tagged with best number tag.

  • The value can be 2 or 3.

  • The best number keyword and argument are mutually exclusive with the best-range range-start range-end keyword and arguments. That is, the configuration of one disallows the configuration of the other.

best-range range-start

(Optional) Matches on paths that are tagged with best n (this starting number or any number in the range specified).

  • The range-start value can be 1, 2, or 3.

  • The best number keyword and argument are mutually exclusive with the best-range range-start range-end keyword and arguments. That is, the configuration of one disallows the configuration of the other.

range-end

(Optional) Matches on paths that are tagged with best n (this ending number or any number in the range specified).

  • The range-end value can be 1, 2, or 3.

  • If the range-start equals the range-end, then one specific path (the nth best path) of the network is matched. Otherwise, the best paths in the range are matched.

group-best

(Optional) Matches on paths that are tagged with the group-best tag.

all

(Optional) Matches on paths that are tagged with the all tag.

Command Default

No matching is performed on additional path advertise sets.

Command Modes


Route-map configuration (config-route-map)

Command History

Release

Modification

15.2(4)S

This command was introduced.

Cisco IOS XE Release 3.7S

This command was integrated into Cisco IOS XE Release 3.7S.

15.3(1)T

This command was integrated into Cisco IOS Release 15.3(1)T.

Usage Guidelines

Use this command in a route map to filter the advertisement of additional paths. Paths that have the same path marking (tag) as the marking that is configured in the match additional-paths advertise-set command match the route map entry (and are permitted or denied). A tag is an advertise-set, as defined in the bgp additional-paths select command.

If match additional-paths advertise-set best number is configured, any path that has the tag best number or a lower number tag matches the route map entry.

You can specify more than one selection policy in one match additional-paths advertise-set command; you must specify at least one selection policy if you use this command.

The best number keyword and argument are mutually exclusive with the best-range range-start range-end keyword and arguments. That is, the configuration of one disallows the configuration of the other. For practical purposes, it is preferable to use best number rather than best-range range-start range-end.

You can configure only one match additional-paths advertise-set command in the route map. If you configure more than one match additional-paths advertise-set command, the latest command overwrites the previous match additional-paths advertise-set command.

You can optionally specify in the route map one or more set commands to set characteristics of a path.

Although you can specify a route map that matches on paths that have marking policies other than the paths you want to advertise, you will typically create a route map that matches on the paths that you want to advertise (specified by the neighbor advertise additional-paths command).

Examples

In the following example, for every address family, there are one or more eBGP neighbors not shown in the configuration that are sending routes to the local device. The eBGP routes learned from these neighbors are advertised toward the neighbors shown in the configuration, and the path attributes are changed. The example configures that:

  • The route map called add_path1 specifies that all the paths are advertised toward neighbor 192.168.101.15, but any path that is marked with the best 2 tag will have its metric set to 780 before being sent toward that neighbor.

  • The route map called add_path2 specifies that any path that is marked with the best 3 tag will have its metric set to 640 and will be advertised toward neighbor 192.168.25.

  • The route map called add_path3 specifies that any path that is marked with the group-best tag will have its metric set to 825 and will be advertised toward neighbor 2001:DB8::1045.

  • In the IPv6 multicast address family, all paths are candidates to be advertised and will be advertised toward neighbor 2001:DB8::1037.

For the rest of advertise-set (not specified in a given route-map), the routes will be denied. If this is not what you want, then you can add another configuration command to permit routes, such as route-map add_pathX permit 20, for example.

router bgp 1
 neighbor 192.168.101.15 remote-as 1
 neighbor 192.168.101.25 remote-as 1
 neighbor 2001:DB8::1045 remote-as 1
 neighbor 2001:DB8::1037 remote-as 1
!
 address-family ipv4 unicast
  bgp additional-paths send receive
  bgp additional-paths select all best 3 group-best
  neighbor 192.168.101.15 activate
  neighbor 192.168.101.15 route-map add_path1 out
  neighbor 192.168.101.15 advertise additional-paths best 2
  exit-address-family 
!
address-family ipv4 multicast
  bgp additional-paths send receive
  bgp additional-paths select all best 3 group-best
  neighbor 192.168.101.25 activate
  neighbor 192.168.101.25 route-map add_path2 out
  neighbor 192.168.101.25 advertise additional-paths best 3
 exit-address-family 
!
 address-family ipv6 unicast
  bgp additional-paths send receive
  bgp additional-paths select group-best
  neighbor 2001:DB8::1045 activate
  neighbor 2001:DB8::1045 route-map add_path3 out
  neighbor 2001:DB8::1045 advertise additional-paths all group-best 
  exit-address-family
!
 address-family ipv6 multicast
  bgp additional-paths send receive
  bgp additional-paths select all
  neighbor 2001:DB8::1037 activate
  neighbor 2001:DB8::1037 advertise additional-paths all 
  exit-address-family
!
route-map add_path1 permit 10
 match additional-paths advertise-set best 2
 set metric 780
route-map add_path1 permit 20
!
route-map add_path2 permit 10
 match additional-paths advertise-set best 3
 set metric 640
!
route-map add_path3 permit 10
 match additional-paths advertise-set group-best
 set metric 825
!
      

Related Commands

Command

Description

bgp additional-paths

Configures BGP to send or receive additional paths for all neighbors in the address family.

bgp additional-paths select

Causes the system to calculate BGP additional paths that can be candidates for advertisement in addition to a bestpath.

neighbor advertise additional-paths

Advertises additional paths for a neighbor based on selection.

neighbor route-map

Applies a route map to incoming or outgoing routes.

route-map (IP)

Defines the conditions for policy routing or redistribution.

match as-path

To match a BGP autonomous system path that is specified by an access list, use the match as-path command in route-map configuration mode. To remove a path list entry, use the no form of this command.

match as-path path-list-number

no match as-path path-list-number

Syntax Description

path-list-number

Access list that specifies an autonomous system path. An integer from 1 to 199.

Command Default

No matching occurs on an autonomous system path specified by an access list.

Command Modes


Route-map configuration (config-route-map)

Command History

Release

Modification

10.0

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

Use the ip as-path access-list command to create an access list that determines which AS path is specified. Then use the match as-path command to create a route map based on matching the access list that determined the AS path.

The values set by the combination of the match as-path and set weight commands override global values. For example, the weights assigned with the match as-path and set weight route-map configuration commands override the weight assigned using the neighbor weight command.

A route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure a second route-map section with an explicit match specified.

Examples

The following example configures a route map that matches on the autonomous system path specified by access list 20:

route-map IGP2BGP
 match as-path 20

Related Commands

Command

Description

ip as-path access-list

Configures an AS path filter using a regular expression.

match community

Matches a BGP community.

match interface (IP)

Distributes routes that have their next hop out one of the interfaces specified.

match ip address

Distributes any routes that have a destination network number address that is permitted by a standard or extended access list, and performs policy routing on packets.

match ip next-hop

Redistributes any routes that have a next hop router address passed by one of the access lists specified.

match ip route-source

Redistributes routes that have been advertised by routers and access servers at the address specified by the access lists.

match metric (IP)

Redistributes routes with the metric specified.

match route-type (IP)

Redistributes routes of the specified type.

match tag

Redistributes routes in the routing table that match the specified tags.

neighbor weight

Assigns weight to a neighbor connection.

route-map (IP)

Defines the conditions for redistributing routes from one routing protocol into another, or enables policy routing.

set as-path

Modifies an autonomous system path for BGP routes.

set automatic-tag

Automatically computes the tag value in a route map configuration.

set community

Sets the BGP communities attribute.

set level (IP)

Indicates where to import routes.

set local-preference

Specifies a preference value for the autonomous system path.

set metric (BGP, OSPF, RIP)

Sets the metric value for a routing protocol.

set metric-type

Sets the metric type for the destination routing protocol.

set next-hop

Specifies the address of the next hop.

set origin (BGP)

Sets the BGP origin code.

set tag (IP)

Sets the value of the destination routing protocol.

set weight

Specifies the BGP weight for the routing table.

match community

To match a Border Gateway Protocol (BGP) community, use the match community command in route-map configuration mode. To remove the match community command from the configuration file and restore the system to its default condition where the software removes the BGP community list entry, use the no form of this command.

match community { standard-list-number | expanded-list-number | community-list-name [exact] }

no match community { standard-list-number | expanded-list-number | community-list-name [exact] }

Syntax Description

standard-list-number

Specifies a standard community list number from 1 to 99 that identifies one or more permit or deny groups of communities.

expanded-list-number

Specifies an expanded community list number from 100 to 500 that identifies one or more permit or deny groups of communities.

community-list-name

The community list name.

exact

(Optional) Indicates that an exact match is required. All of the communities and only those communities specified must be present.

Command Default

No community list is matched by the route map.

Command Modes


Route-map configuration (config-route-map)

Command History

Release

Modification

12.1

This command was introduced.

12.1(9)E

Named community list support was integrated into Cisco IOS Release 12.1(9)E.

12.2(8)T

Named community list support was integrated into Cisco IOS Release 12.2(8)T.

12.0(22)S

The maximum number of expanded extended community list numbers was changed from 199 to 500 in Cisco IOS Release 12.0(22)S.

12.2(14)S

The maximum number of expanded community lists was changed from 199 to 500 and named community list support were integrated into Cisco IOS Release 12.2(14)S.

12.2(15)T

The maximum number of expanded extended community list numbers was changed from 199 to 500 in Cisco IOS Release 12.2(15)T.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

A route map can have several parts. Any route that does not match at least one match command relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure a second route-map section with an explicit match specified.

Matching based on community list number is one of the types of match commands applicable to BGP.

Examples

The following example shows that the routes matching community list 1 will have the weight set to 100. Any route that has community 109 will have the weight set to 100.

Router(config)# ip community-list 1 permit 109
Router(config)# route-map set_weight
Router(config-route-map)#  match community 1
Router(config-route-map)# set weight 100

The following example shows that the routes matching community list 1 will have the weight set to 200. Any route that has community 109 alone will have the weight set to 200.

Router(config)# ip community-list 1 permit 109
Router(config)# route-map set_weight
Router(config-route-map)# match community
 1 exact
Router(config-route-map)# set weight 200

In the following example, the routes that match community list LIST_NAME will have the weight set to 100. Any route that has community 101 alone will have the weight set to 100.

Router(config)# ip community-list LIST_NAME permit 101
Router(config)# route-map set_weight
Router(config-route-map)# match community LIST_NAME 
Router(config-route-map)# set weight 100

The following example shows that the routes that match expanded community list 500. Any route that has extended community 1 will have the weight set to 150.

Router(config)# ip community-list 500 permit [0-9]*
Router(config)# route-map MAP_NAME permit 10
Router(config-route-map)# match extcommunity 500
Router(config-route-map)# set weight 150

Related Commands

Command

Description

ip community-list

Creates a community list for BGP and controls access to it.

route-map (IP)

Defines the conditions for redistributing routes from one routing protocol into another.

set weight

Specifies the BGP weight for the routing table.

match extcommunity

To match Border Gateway Protocol (BGP) or Enhanced Interior Gateway Routing Protocol (EIGRP) extended community list attributes, use the match extcommunity command in route-map configuration mode. To remove the match extcommunity command from the configuration file and remove the BGP or EIGRP extended community list attribute entry, use the no form of this command.

match extcommunity extended-community-list-name

no match extcommunity extended-community-list-name

Syntax Description

extended-community-list-name

Name of an extended community list.

Command Default

BGP and EIGRP extended community list attributes are not matched.

Command Modes


Route-map configuration (config-route-map)

Command History

Release

Modification

12.1

This command was introduced.

12.0(22)S

The maximum number of expanded extended community list numbers was changed from 199 to 500 in Cisco IOS Release 12.0(22)S.

12.2(15)T

The maximum number of expanded extended community list numbers was changed from 199 to 500 in Cisco IOS Release 12.2(15)T.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

Cisco IOS XE Release 2.1

This command was integrated into Cisco IOS XE Release 2.1.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

15.0(1)M

This command was modified. Support for EIGRP was added.

12.2(33)SRE

This command was modified. Support for EIGRP was added.

Cisco IOS XE Release 2.5

This command was modified. Support for EIGRP was added.

12.2(33)XNE

This command was modified. Support for EIGRP was added.

Usage Guidelines

Extended community attributes are used to configure, filter, and identify routes for virtual routing and forwarding instances (VRFs) and Multiprotocol Label Switching (MPLS) Virtual Private Networks (VPNs).

The match extcommunity command is used to configure match clauses that use extended community attributes in route maps. All of the standard rules of match and set clauses apply to the configuration of extended community attributes.

Examples

The following example shows that the routes that match extended community list 500 will have the weight set to 100. Any route that has extended community 1 will have the weight set to 100.

Router(config)# ip extcommunity-list 500 rt 100:2
Router(config-extcomm-list)# exit
Router(config)# route-map MAP_NAME permit 10
Router(config-route-map)# match extcommunity 1
Router(config-route-map)# set weight 100

Related Commands

Command

Description

ip extcommunity-list

Creates an extended community list for BGP and controls access to it.

route-map (IP)

Defines the conditions for redistributing routes from one routing protocol into another.

set extcommunity

Sets BGP extended community attributes.

set weight

Specifies the BGP weight for the routing table.

show ip extcommunity-list

Displays routes that are permitted by the extended community list.

show route-map

Displays configured route maps.

match local-preference

To configure a route map to match routes based on the Border Gateway Protocol (BGP) local-preference attribute, use the match local-preference command in route-map configuration mode. To remove the match clause entry from the route map, use the no form of this command.

match local-preference value

no match local-preference value

Syntax Description

value

The local preference value. This argument can be entered as a number from 0 to 4294967295.

Command Default

Cisco IOS software uses a default value of 100 for the local-preference attribute. However, a local-preference value must be entered when configuring a match clause with this command.

Command Modes


Route-map configuration (config-route-map)

Command History

Release

Modification

12.3(14)T

This command was introduced.

12.2(30)S

This command was integrated into Cisco IOS Release 12.2(30)S.

Usage Guidelines

The match local-preference command is used to filter routes based on the value of the local preference attribute. The local-preference attribute is a well-known discretionary attribute that is used to set the preference for an exit point within an autonomous system. The route with the highest local-preference value is preferred by the BGP best path selection process.

Redistributing OER Injected Routes

Optimized Edge Routing (OER) uses a local-preference value of 5000 (default) to move traffic to the preferred exit point in a BGP network (This value can be configured on the OER master controller). The match local-preference command can be used to redistribute OER injected routes within an autonomous system that is monitored and controlled by OER.

Examples

The following example configures the route-map name RED to match OER injected routes:

Router(config)# 
route-map RED permit 10 
Router(config-route-map)# 
match local-preference 5000
 

Related Commands

Command

Description

bgp default local-preference

Changes the default local-preference value.

route-map (IP)

Defines conditions for redistributing routes.

set local-preference

Applies a local-preference value to routes that pass the match clause.

match policy-list

To configure a route map to evaluate and process a Border Gateway Protocol (BGP) policy list in a route map, use the match policy-list command in route-map configuration mode. To remove a path list entry, use the no form of this command.

match policy-list policy-list-name

no match policy-list policy-list-name

Syntax Description

policy-list-name

Name of the policy list to evaluate and process within the route map.

Command Default

This command is not enabled by default.

Command Modes


Route-map configuration (config-route-map)

Command History

Release

Modification

12.0(22)S

This command was introduced.

12.2(15)T

This command was integrated into 12.2(15)T.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

Usage Guidelines

When a policy list is referenced within a route map, all the match statements within the policy list are evaluated and processed.

Two or more policy lists can be configured with a route map. Policy lists can be configured within a route map to be evaluated with AND semantics or OR semantics.

Policy lists can also coexist with any other preexisting match and set statements that are configured within the same route map but outside of the policy lists.

When multiple policy lists perform matching within a route map entry, all policy lists match on the incoming attribute only.

Examples

The following configuration example creates a route map that references policy lists and separate match and set clauses in the same configuration:

Router(config)# route-map MAP-NAME-1 10
Router(config-route-map)# match ip-address 1
Router(config-route-map)# match policy-list POLICY-LIST-NAME-1 
Router(config-route-map)# set community 10:1
Router(config-route-map)# set local-preference 140
Router(config-route-map)# end

The following configuration example creates a route map that references policy lists and separate match and set clauses in the same configuration. This example processes the policy lists named POLICY-LIST-NAME-2 and POLICY-LIST-NAME-3 with OR semantics. A match is required from only one of the policy lists.

Router(config)# route-map MAP-NAME-2 10
Router(config-route-map)# match policy-list POLICY-LIST-NAME-2 POLICY-LIST-NAME-3
Router(config-route-map)# set community 10:1
Router(config-route-map)# set local-preference 140
Router(config-route-map)# end

Related Commands

Command

Description

ip policy-list

Creates a BGP policy list.

match as-path

References a policy list within a route map for evaluation and processing.

match community

Matches a BGP community.

match interface (IP)

Distributes routes that have their next hop out one of the interfaces specified.

match ip address

Distributes any routes that have a destination network number address that is permitted by a standard or extended access list, and performs policy routing on packets.

match ip next-hop

Redistributes any routes that have a next hop router address passed by one of the access lists specified.

match ip route-source

Redistributes routes that have been advertised by routers and access servers at the address specified by the access lists.

match metric (IP)

Redistributes routes with the metric specified.

match route-type (IP)

Redistributes routes of the specified type.

match tag

Redistributes routes in the routing table that match the specified tags.

neighbor weight

Assigns weight to a neighbor connection.

route-map (IP)

Defines the conditions for redistributing routes from one routing protocol into another, or enables policy routing.

match rpki

To match Border Gateway Protocol (BGP) routes that have the specified Resource Public Key Infrastructure (RPKI) state, use the match rpki command in route-map configuration mode. To remove the match rpki command from the route map, use the no form of this command.

match rpki { not-found | invalid | valid }

no match rpki { not-found | invalid | valid }

Syntax Description

not-found

Matches on the RPKI state Not Found.

invalid

Matches on the RPKI state Invalid.

valid

Matches on the RPKI state Valid.

Command Default

No RPKI state is matched by the route map.

Command Modes


Route-map configuration (config-route-map)

Command History

Release

Modification

XE 3.5S

This command was introduced.

15.2(1)S

This command was integrated into Cisco IOS Release 15.2(1)S.

15.2(4)S

This command was implemented on the Cisco 7200 series routers.

Usage Guidelines

Use this command to create a custom policy for the treatment of valid, not-found, and invalid prefixes. We recommend that you also use the bgp bestpath prefix-validate allow-invalid command when configuring a route map to match on RPKI states.

By default, the router overrides all other preferences to reject routes that are in an invalid state. You must explicitly configure the bgp bestpath prefix-validate allow-invalid command if you want to use a route map to do something such as permit invalid prefixes, but with a non-default local preference.

Examples

In the following example, a route map named rtmap-PEX1-3 sets a local preference of 50 for invalid prefix/AS pairs, 100 for not-found prefix/AS pairs, and 200 for valid prefix/AS pairs. The local preference values are set for incoming routes from the neighbor at 10.0.102.1. The neighbor is an External Border Gateway Protocol (EBGP) peer.

router bgp 65000
 address-family ipv4 unicast
 neighbor 10.0.102.1 route-map rtmap-PEX1-3 in
 bgp bestpath prefix-validate allow-invalid
!
route-map rtmap-PEX1-3 permit 10
 match rpki invalid
 set local-preference 50
!
route-map rtmap-PEX1-3 permit 20
 match rpki not-found
 set local-preference 100
!
route-map rtmap-PEX1-3 permit 30
 match rpki valid
 set local-preference 200
!
route-map rtmap-PEX1-3 permit 40

Related Commands

Command

Description

bgp bestpath prefix-validate allow-invalid

Allows invalid prefixes to be used as the bestpath even if valid prefixes are available.

bgp rpki server

Connects to an RPKI server and enables the validation of BGP prefixes based on the AS from which the prefix originates.

neighbor announce rpki state

Sends and receives the RPKI state and prefix/AS pairs to and from an IBGP neighbor.

route-map

Defines the conditions for subjecting prefixes to policies.

show ip bgp rpki servers

Displays the current state of communication with RPKI servers.

show ip bgp rpki table

Displays the currently cached list of networks and associated AS numbers received from the RPKI server.

match source-protocol

To match Enhanced Interior Gateway Routing Protocol (EIGRP) external routes based on a source protocol and autonomous system number, use the match source-protocol command in route-map configuration mode. To remove the protocol to be matched, use the no form of this command.

match source-protocol source-protocol [autonomous-system-number]

no match source-protocol source-protocol [autonomous-system-number]

Syntax Description

source-protocol

Protocol to match. The valid keywords are bgp, connected, eigrp, isis, ospf, rip, and static. There is no default.

autonomous-system-number

(Optional) Autonomous system number. This argument is not applicable to the connected, rip, and static keywords. The range is from 1 to 65535.

  • In Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, and later releases, 4-byte autonomous system numbers are supported in the range from 65536 to 4294967295 in asplain notation and in the range from 1.0 to 65535.65535 in asdot notation.

  • In Cisco IOS Release 12.0(32)S12, 12.4(24)T, and Cisco IOS XE Release 2.3, 4-byte autonomous system numbers are supported in the range from 1.0 to 65535.65535 in asdot notation only.

For more details about autonomous system number formats, see the router bgp command.

Command Default

EIGRP external routes are not matched on a source protocol and autonomous system number.

Command Modes


Route-map configuration (config-route-map)

Command History

Release

Modification

12.3(8)T

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.

12.0(32)S12

This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.

12.0(32)SY8

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

12.4(24)T

This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.

Cisco IOS XE Release 2.3

This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.

12.2(33)SXI1

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

12.0(33)S3

This command was modified. Support for asplain notation was added and the default format for 4-byte autonomous system numbers is now asplain.

Cisco IOS XE Release 2.4

This command was modified. Support for asplain notation was added and the default format for 4-byte autonomous system numbers is now asplain.

12.2(33)SRE

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

12.2(33)XNE

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

15.2(1)E

This command was integrated into Cisco IOS Release 15.2(1)E.

Usage Guidelines

This command may not be useful with a redistribution operation that employs route maps because redistribution usually requires the configuration of a source protocol and an autonomous system value in order to redistribute. In many cases, it is more useful to configure a route map that includes matching the route type based on the source protocol and autonomous system using the distribute-list command for EIGRP.

Examples

The following example shows how to configure a route map to match a source protocol of BGP and an autonomous system 45000. When the match clause is true, the tag value of the destination routing protocol is set to 5. The route map is used to distribute incoming packets for an EIGRP process.

route-map metric_source
 match source-protocol bgp 45000
 set tag 5
!
router eigrp 1
 network 172.16.0.0
 distribute-list route-map metric_source in

The following example shows how to configure a route map to match a source protocol of BGP and a 4-byte autonomous system of 65538 in asplain format. When the match clause is true, the tag value of the destination routing protocol is set to 5. The route map is used to distribute incoming packets for an EIGRP process. This example requires Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, or a later release.

route-map metric_source
 match source-protocol bgp 65538
 set tag 5
!
router eigrp 1
 network 172.16.0.0
 distribute-list route-map metric_source in

The following example shows how to configure a route map to match a source protocol of BGP and a 4-byte autonomous system of 1.2 in asdot format. When the match clause is true, the tag value of the destination routing protocol is set to 5. The route map is used to distribute incoming packets for an EIGRP process. This example requires Cisco IOS Release 12.0(32)S12, 12.4(24)T, or Cisco IOS XE Release 2.3 where asdot notation is the only format for 4-byte autonomous system numbers. This configuration can also be performed using Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, or a later release.

route-map metric_source
 match source-protocol bgp 1.2
 set tag 5
!
router eigrp 1
 network 172.16.0.0
 distribute-list route-map metric_source in

Related Commands

Command

Description

distribute-list

Filters networks received in updates.

match tag

Redistributes routes in the routing table that match the specified tags.

route-map (IP)

Defines the conditions for redistributing routes from one routing protocol into another, or enables policy routing.

router bgp

Configures the BGP routing process.

set as-path

Modifies an autonomous system path for BGP routes.

set tag (IP)

Sets a tag value of the destination routing protocol.

maximum-paths eibgp

To enable multipath load sharing among external Border Gateway Protocol (eBGP) and internal BGP (iBGP) routes, use the maximum-paths eibgp command in address family configuration mode. To disable multipath load sharing for eBGP and iBGP routes, use the no form of this command.

maximum-paths eibgp number-of-paths [ import number-of-import-paths ]

no maximum-paths eibgp number-of-paths [ import number-of-import-paths ]

Syntax Description

number-of-paths

Number of routes to install into the routing table. See the “Usage Guidelines” section for the number of paths that can be configured with this argument.

import number-of-import-paths

(Optional) Specifies the number of redundant paths that can be configured as backup multipaths for a virtual routing and forwarding (VRF) table. This keyword can be configured only under a VRF instance in address family configuration mode.

Note   

We recommend that this keyword is enabled only when needed and that the number of import paths be kept to the minimum (typically, not more than two paths). For more information, see the “Usage Guidelines” section of this command page.

Command Default

BGP, by default, will install only one best path in the routing table.

Command Modes


Address family configuration (config-router-af)

Command History

Release

Modification

12.2(4)T

This command was introduced.

12.0(24)S

This command was integrated into Cisco IOS Release 12.0(24)S.

12.0(25)S

This command was modified. The import keyword was added.

12.3(2)T

This command was modified. The maximum number of parallel routes was increased from 6 to 16.

12.2(18)SXE

This command was integrated into Cisco IOS Release 12.2(18)SXE.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

15.0(1)M

This command was modified. The import keyword was replaced by the import path selection and import path limit commands.

12.2(33)SRE

This command was integrated into Cisco IOS Release 12.2(33)SRE.

Cisco IOS XE 2.6

This command was integrated into Cisco IOS XE Release 2.6.

15.0(1)SY

This command was integrated into Cisco IOS Release 15.0(1)SY.

Cisco IOS XE 3.10S

This command was modified. The functionality to configure the command on non-VRF address families was added.

15.3(3)S

This command was modified. The functionality to configure the command on non-VRF address families was added.

15.4(1)T

This command was integrated into Cisco IOS Release 15.4(1)T.

Usage Guidelines

The maximum-paths eibgp command is used to enable BGP multipath load sharing in a Multiprotocol Label Switching (MPLS) VPN using eBGP and iBGP routes. You can configure this command under VRF and non-VRF address families. The number of multipaths is configured separately for each VRF.

The number of paths that can be configured is determined by the version of Cisco IOS software as shown in the following list:

  • Cisco IOS Release 12.0S-based software: 8 paths

  • Cisco IOS Release 12.3T, 12.4, 12.4T, and 15.0-based software: 16 paths

  • Cisco IOS Release 12.2S-based software: 32 paths

The maximum-paths eibgp command cannot be configured with the maximum-paths or maximum-paths ibgp command because the maximum-paths eibgp command is a superset of these commands.


Note


The configuration of this command does not override the existing outbound routing policy.


Configuring VRF Import Paths

A VRF will import only one path (best path) per prefix from the source VRF table, unless the prefix is exported with a different route target. If the best path goes down, the destination will not be reachable until the next import event occurs, and then a new best path will be imported into the VRF table. The import event runs every 15 seconds by default.

The import keyword allows the network operator to configure the VRF table to accept multiple redundant paths in addition to the best path. An import path is a redundant path, and it can have a next hop that matches an installed multipath. This keyword should be used when multiple paths with identical next hops are available to ensure optimal convergence times. A typical application of this keyword is to configure redundant paths in a network that has multiple route reflectors for redundancy.

The maximum number of import paths that can be configured in Cisco IOS Release 12.2SY-based software is 16.


Note


Configuring redundant paths with the import keyword can increase CPU and memory utilization significantly, especially in a network where there are many prefixes to learn and a large number of configured VRFs. We recommend that this keyword be configured only as necessary and that the minimum number of redundant paths be configured (typically, not more than two).


In Cisco IOS Releases 15.0(1)M and 12.2(33)SRE, and in later releases, the import keyword was replaced by the import path selection and import path limit commands. If the import keyword is configured, the configuration is converted to the new commands, as show in the following example:

Device(config-router-af)# maximum-paths eibgp import 3
 
%NOTE: Import option has been deprecated.
%      Converting to 'import path selection all; import path limit 3'.

Examples

In the following example, the router is configured to install six eBGP or iBGP routes into the VRF routing table:

Device(config)# router bgp 64496
Router(config-router)# address-family ipv4 vrf vrf-1
Router(config-router-af)# maximum-paths eibgp 6 

The following example shows how to configure this command on a non-VRF address family.

Device(config)# router bgp 64498
Device(config-router)# address-family ipv4 unicast
Device(config-router-af)# maximum-paths eibgp 4
 

Related Commands

Command

Description

import path limit

Specifies the maximum number of BGP paths, per VRF importing net, that can be imported from an exporting net.

import path selection

Specifies the BGP import-path selection policy for a VRF instance.

maximum-paths

Controls the maximum number of parallel routes an IP routing protocol can support.

maximum-paths ibgp

Configures the number of equal-cost or unequal-cost routes that BGP will install in the routing table.

show ip bgp

Displays information about entries in the BGP routing table.

show ip bgp vpnv4

Displays VPNv4 address information from the BGP table entries in the BGP routing table.

maximum-paths ibgp

To control the maximum number of parallel internal Border Gateway Protocol (iBGP) routes that can be installed in a routing table, use the maximum-paths ibgp command in router or address family configuration mode. To restore the default value, use the no form of this command.

Router Configuration Mode

maximum-paths ibgp number-of-paths

no maximum-paths ibgp number-of-paths

Under VRF in Address Family Configuration Mode

maximum-paths ibgp { number-of-paths [ import number-of-import-paths ] | unequal-cost number-of-import-paths }

no maximum-paths ibgp { number-of-paths [ import number-of-import-paths ] | unequal-cost number-of-import-paths }

Syntax Description

number-of-paths

Number of routes to install to the routing table. See the “Usage Guidelines” section for the number of paths that can be configured with this argument.

import number-of-import-paths

(Optional) Specifies the number of redundant paths that can be configured as backup multipaths for a virtual routing and forwarding (VRF) instance. This keyword can be configured only under a VRF in address family configuration mode.

Note   

We recommend that this keyword is enabled only where needed and that the number of import paths be kept to the minimum (typically, not more than two paths). For more information, see the related note in the “Usage Guidelines” section of this command page.

unequal-cost number-of-import-paths

Specifies the number of unequal-cost routes to install in the routing table. See the “Usage Guidelines” section for the number of paths that can be configured. This keyword can be configured only under a VRF instance in address family configuration mode.

Command Default

BGP, by default, will install only one best path in the routing table.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.2(2)T

This command was introduced.

12.0(25)S

This command was modified. The import keyword was added.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.2(14)SX

This command was integrated into Cisco IOS Release 12.2(14)SX.

12.3

This command was modified. The import keyword was added.

12.3(2)T

This command was modified. The maximum number of parallel routes was increased from 6 to 16.

12.2(25)S

This command was integrated into Cisco IOS Release 12.2(25)S for use in IPv6.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

15.0(1)M

This command was modified. The import keyword was replaced by the import path selection and import path limit commands.

12.2(33)SRE

This command was modified. The import keyword was replaced by the import path selection and import path limit commands.

Cisco IOS XE 2.6

This command was integrated into Cisco IOS XE Release 2.6.

15.0(1)SY

This command was integrated into Cisco IOS Release 15.0(1)SY.

Usage Guidelines

The maximum-paths ibgp command is used to configure equal-cost or unequal-cost multipath load sharing for iBGP peering sessions. In order for a route to be installed as a multipath in the BGP routing table, the route cannot have a next hop that is the same as another route that is already installed. The BGP routing process will still advertise a best path to iBGP peers when iBGP multipath load sharing is configured. For equal-cost routes, the path from the neighbor with the lowest router ID is advertised as the best path.

To configure BGP equal-cost multipath load sharing, all path attributes must be the same. The path attributes include weight, local preference, autonomous system path (entire attribute and not just the length), origin code, Multi Exit Discriminator (MED), and Interior Gateway Protocol (IGP) distance.

The number of paths that can be configured is determined by the version of Cisco IOS software as shown in the following list:

  • Cisco IOS Release 12.0S-based software: 8 paths

  • Cisco IOS Release 12.3T, 12.4, 12.4T, and 15.0-based software: 16 paths

  • Cisco IOS Release 12.2S-based software: 32 paths


Note


In IPv6, the maximum-paths ibgp command does not work for prefixes learned from iBGP neighbors that have been configured to distribute a Multiprotocol Label Switching (MPLS) label with its IPv6 prefix advertisements. If multiple routes exist for such prefixes, all of them are inserted into the Routing Information Base (RIB) when the maximum-paths ibgp command is configured, but only one is used and no load balancing occurs between equal-cost paths. The maximum-paths ibgp command works with 6PE only in Cisco IOS Release 12.2(25)S and subsequent 12.2S releases.


Configuring VRF Import Paths

A VRF will import only one path (the best path) per prefix from the source VRF table, unless the prefix is exported with a different route target. If the best path goes down, the destination will not be reachable until the next import event occurs, and then a new best path will be imported into the VRF table. The import event runs every 15 seconds by default.

The import keyword allows the network operator to configure the VRF table to accept multiple redundant paths in addition to the best path. An import path is a redundant path, and it can have a next hop that matches an installed multipath. This keyword should be used when multiple paths with identical next hops are available to ensure optimal convergence times. A typical application of this keyword is to configure redundant paths in a network that has multiple route reflectors for redundancy.

The maximum number of import paths that can be configured in Cisco IOS Release 12.2SY-based software is 16.


Note


Configuring redundant paths with the import keyword can increase CPU and memory utilization significantly, especially in a network where there are many prefixes to learn and a large number of configured VRFs. It is recommended that this keyword be configured only as necessary and that the minimum number of redundant paths be configured (typically, not more than two).


In Cisco IOS Releases 15.0(1)M and 12.2(33)SRE, and in later releases, the import keyword was replaced by the import path selection and import path limit commands. If the import keyword is configured, the configuration is converted to the new commands, as show in the following example:

Router(config-router-af)# maximum-paths ibgp import 3
 
%NOTE: Import option has been deprecated.
%      Converting to 'import path selection all; import path limit 3'.

Examples

The following example configuration installs three parallel iBGP paths in a non-MPLS topology:

Router(config)# router bgp 100
Router(config-router)# maximum-paths ibgp 3

The following example configuration installs three parallel iBGP paths in an MPLS Virtual Private Network (VPN) topology:

Router(config)# router bgp 100
Router(config-router)# address-family ipv4 unicast vrf vrf-A
Router(config-route-af)# maximum-paths ibgp 3 

The following example configuration installs two parallel routes in the VRF table:

Router(config)# router bgp 100 
Router(config-router)# address-family ipv4 vrf vrf-B 
Router(config-router-af)# maximum-paths ibgp 2 import 2 
Router(config-router-af)# end 

The following example configuration installs two parallel routes in the VRF table:

Router(config)# router bgp 100
Router(config-router)# address-family ipv4 vrf vrf-C 
Router(config-router-af)# maximum-paths ibgp import 2
Router(config-router-af)# end
 

Related Commands

Command

Description

import path limit

Specifies the maximum number of BGP paths, per VRF importing net, that can be imported from an exporting net.

import path selection

Specifies the BGP import path selection policy for a specific VRF instance.

maximum-paths

Controls the maximum number of parallel routes an IP routing protocol can support.

maximum-paths ibgp

Configures the number of equal-cost or unequal-cost routes that BGP will install in the routing table.

show ip bgp

Displays entries in the BGP routing table.

show ip bgp vpnv4

Displays VPNv4 address information from the BGP table entries in the BGP routing table.

mvpn single-forwarder-selection highest-ip-address

To configure the Border Gateway Protocol (BGP) Multicast VPN (MVPN) Upstream Multicast Hop (UMH) chosen via the highest ip address, use the mvpn single-forwarder-selection highest-ip-address command in address family configuration mode.

To disable the BGP MVPN hop, use the no form of this command.

mvpn single-forwarder-selection highest-ip-address

no mvpn single-forwarder-selection highest-ip-address

Command Default

Command Modes

Address family configuration (config-router-af)

Command History

Release Modification

Cisco IOS XE Release 3.10S

This command was introduced.

Usage Guidelines

BGP uses the Upstream Multicast Hop (UMH) algorithm to select Reverse Path Forwarding (RPF). To configure a UMH, the BGP neighbors must be activated under the appropriate address-family. By default, single path selection by BGP VPN is based on the BGP best path algorithm.

Examples

The following example shows how to configure a BGP MVPN UMH on the device:

Device(config)# configure terminal
Device(config)# router bgp 100
Device(config-router)# address-family ipv4 vrf test
Device(config-router-af)# mvpn single-forwarder-selection highest-ip-address

Related Commands

Command

Description

address-family mvpn

Enter address family configuration mode to configure a routing session using MVPN address information.

show bgp mvpn

Display entries in the BGP routing table for MVPN sessions.

neighbor accept-route-legacy-rt

To create Route Target Constrain (RTC) from the VPN prefix received from a legacy route target (RT) peer with special communities, use the neighbor accept-route-legacy-rt command in address family configuration mode. To remove the RT, use the no form of this command.

neighbor { ip-address | peer-group-name | ipv6-address } accept-route-legacy-rt

no neighbor { ip-address | peer-group-name | ipv6-address } accept-route-legacy-rt

Syntax Description

ip-address

IPv4 address for advertising the best external path.

peer-group-name

Name of the Boarder Gateway Protocol (BGP) peer group.

ipv6-address

IPv6 address for advertising the best external path.

Command Default

No legacy RT is configured.

Command Modes

Address family configuration (config-router-af)

Command History

Release

Modification

15.4(1)S

This command was introduced.

Cisco IOS XE Release 3.11S

This command was integrated into Cisco IOS XE Release 3.11S.

Usage Guidelines

Use this command when you are configuring the BGP—RTC for Legacy PE feature.

The neighbor accept-route-legacy-rt command is configured on the route reflector (RR). RRs identify routes from legacy provider edge (PE) devices for retrieving RT membership information and filter VPN routes to legacy PE devices. The RR creates the RT filter list for each legacy client by collecting the entire set of route targets.

Examples

In the following example, the neighbor at 10.1.1.1 is configured as legacy RT:

Device# configure terminal
Device(config)# router bgp 65000
Device(config-router)# address-family vpnv4 unicast
Device(config-router-af)# neighbor 10.1.1.1 activate
Device(config-router-af)# neighbor 10.1.1.1 accept-route-legacy-rt
Device(config-router-af)# exit address-family

Related Commands

Command

Description

address-family rtfilter unicast

Enables RTC with a BGP peer.

neighbor default-originate

Allows a BGP speaker (the local router) to send the default route 0:0:0:0 to a neighbor for use as a default route.

router bgp

Configures the BGP routing process.

neighbor activate

To enable the exchange of information with a Border Gateway Protocol (BGP) neighbor, use the neighbor activate command in address family configuration mode or router configuration mode. To disable the exchange of an address with a BGP neighbor, use the no form of this command.

neighbor { ip-address | peer-group-name | ipv6-address% } activate

no neighbor { ip-address | peer-group-name | ipv6-address% } activate

Syntax Description

ip-address

IP address of the neighboring router.

peer-group-name

Name of the BGP peer group.

ipv6-address

IPv6 address of the BGP neighbor.

%

(Optional) IPv6 link-local address identifier. This keyword needs to be added whenever a link-local IPv6 address is used outside the context of its interface.

Command Default

The exchange of addresses with BGP neighbors is enabled for the IPv4 address family. Enabling address exchange for all other address families is disabled.


Note


Address exchange for address family IPv4 is enabled by default for each BGP routing session configured with the neighbor remote-as command unless you configure the no bgp default ipv4-activate command before configuring the neighbor remote-as command, or you disable address exchange for address family IPv4 with a specific neighbor by using the no neighbor activate command.


Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

11.0

This command was introduced.

12.0(5)T

Support for address family configuration mode and the IPv4 address family was added.

12.2(2)T

The ipv6-address argument and support for the IPv6 address family were added.

12.0(21)ST

This command was integrated into Cisco IOS Release 12.0(21)ST.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SRB

The % keyword was added

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.

Cisco IOS XE Release 2.1

This command was introduced on Cisco ASR 1000 Series Routers.

15.1(2)SNG

This command was implemented on the Cisco ASR 901 Series Aggregation Services Routers.

Usage Guidelines

Use this command to advertise address information in the form of an IP or IPv6 prefix. The address prefix information is known as Network Layer Reachability Information (NLRI) in BGP.

The % keyword is used whenever link-local IPv6 addresses are used outside the context of their interfaces. This keyword does not need to be used for non-link-local IPv6 addresses.


Note


The use of the no form of the neighbor activate command will remove all configurations associated with the neighbor both inside and outside address family configuration mode. This command is not the same as the neighbor shutdown command, and you should not use this command to disconnect a BGP adjacency.


Examples

The following example shows how to enable address exchange for address family vpnv4 for all neighbors in the BGP peer group named PEPEER and for the neighbor 10.0.0.44:

Router(config)# address-family vpnv4
Router(config-router-af)# neighbor PEPEER activate
Router(config-router-af)# neighbor 10.0.0.44 activate
Router(config-router-af)# exit-address-family

Examples

The following example shows how to enable address exchange for address family IPv4 unicast for all neighbors in the BGP peer group named group1 and for the BGP neighbor 172.16.1.1:

Device(config)# address-family ipv4 unicast
Device(config-router-af)# neighbor group1 activate
Device(config-router-af)# neighbor 172.16.1.1 activate

Examples

The following example shows how to enable address exchange for address family IPv6 for all neighbors in the BGP peer group named group2 and for the BGP neighbor 7000::2:

Device(config)# address-family ipv6
Device(config-router-af)# neighbor group2 activate
Device(config-router-af)# neighbor 7000::2 activate

The following example shows that the no command will remove all configurations associated with a neighbor both inside and outside the address family configuration mode. The first set of commands shows the configuration for a specific neighbor.

Device(config)# router bgp 64496
Device(config-router)# bgp log neighbor changes
Device(config-router)# neighbor 10.0.0.1 remote-as 64497
Device(config-router)# neighbor 10.0.0.1 update-source Loopback0
Device(config-router)# address-family ipv4
Device(config-router-af)# no synchronization
Device(config-router-af)# no neighbor 10.0.0.1 activate
Device(config-router-af)# no auto-summary
Device(config-router-af)# exit-address-family
Device(config-router)address-family vpnv4
Device(config-router-af)# neighbor 10.0.0.1 activate
Device(config-router-af)# neighbor 10.0.0.1 send-community extended
Device(config-router-af)# exit-address-family
Device(config-router)# address-family ipv4 vrf vrf1
Device(config-router-af)# no synchronization
Device(config-router-af)# redistribute connected
Device(config-router-af)# neighbor 192.168.1.4 remote-as 100
Device(config-router-af)# neighbor 192.168.1.4 version 4
Device(config-router-af)# neighbor 192.168.1.4 activate
Device(config-router-af)# neighbor 192.168.1.4 weight 200
Device(config-router-af)# neighbor 192.168.1.4 prefix-list test out
Device(config-router-af)# exit-address-family

The following example shows the router configuration after the use of the no command.

Device(config)# router bgp 64496
Device(config-router)# address-family ipv4 vrf vrf1
Device(config-router-af)# no neighbor 192.168.1.4 activate
01:01:19: %BGP_SESSION-5-ADJCHANGE: neighbor 192.168.1.4 IPv4 Unicast vpn vrf vrf1 topology base removed from session  Neighbor deleted
01:01:19: %BGP-5-ADJCHANGE: neighbor 192.168.1.4 vpn vrf vrf1 Down Neighbor deleted
Device(config-router-af)# do show running-config | begin router bgp

router bgp 64496
bgp log-neighbor-changes
neighbor 10.0.0.1 remote-as 64496
neighbor 10.0.0.1 update-source Loopback0
!
address-family ipv4
  no synchronization
  no neighbor 10.0.0.1 activate
  no auto-summary
exit-address-family
!
address-family vpnv4
  neighbor 10.0.0.1 activate
  neighbor 10.0.0.1 send-community extended
exit-address-family
!
address-family ipv4 vrf vrf1
  no synchronization
  redistribute connected
exit-address-family 

This example shows the router configuration when the neighbor is reactivated.

Device(config)# router bgp 64496
Device(config-router)# address-family ipv4 vrf vrf1
Device(config-router-af)# neighbor 192.168.1.4 activate
01:02:26: %BGP-5-ADJCHANGE: neighbor 192.168.1.4 vpn vrf vrf1 Up
Device(config-router-af)# do show running-config | begin router bgp

router bgp 64496
bgp log-neighbor-changes
neighbor 10.0.0.1 remote-as 64496
neighbor 10.0.0.1 update-source Loopback0
!
address-family ipv4
  no synchronization
  no neighbor 10.0.0.1 activate
  no auto-summary
exit-address-family
!
address-family vpnv4
  neighbor 10.0.0.1 activate
  neighbor 10.0.0.1 send-community extended
exit-address-family
!
address-family ipv4 vrf vrf1
  no synchronization
  redistribute connected
  neighbor 192.168.1.4 remote-as 100
  neighbor 192.168.1.4 version 4
  neighbor 192.168.1.4 activate
exit-address-family
 

Related Commands

Command

Description

address-family ipv4

Places the router in address family configuration mode for configuring routing sessions, such as BGP, that use standard IPv4 address prefixes.

address-family ipv6

Places the router in address family configuration mode for configuring routing sessions, such as BGP, that use standard IPv6 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions, such as BGP, that use standard VPNv4 address prefixes.

address-family vpnv6

Places the router in address family configuration mode for configuring routing sessions, such as BGP, that use standard VPNv6 address prefixes.

exit-address-family

Exits from the address family submode.

neighbor remote-as

Adds an entry to the BGP or multiprotocol BGP neighbor table.

neighbor additional-paths

To configure the local router with the ability to send and receive additional path information for a neighbor or peer group, use the neighbor additional-paths command in address family configuration mode. To remove the per-neighbor or per-peer group configuration of the sending and receiving of additional paths, use the no form of the command.

neighbor { ip-address | ipv6-address | peer-group-name } additional-paths { send [receive] | receive | disable }

no neighbor { ip-address | ipv6-address | peer-group-name } additional-paths { send [receive] | receive }

Syntax Description

ip-address

IP address of the neighbor.

ipv6-address

IPv6 address of the neighbor.

peer-group-name

Name of the peer group of peers.

send

(Optional) Specifies that the local device can send additional paths for the specified neighbor or peer group.

receive

(Optional) Specifies that the local device can receive additional paths for the specified neighbor or peer group.

disable

(Optional) Overrides template or address family configurations that enable the sending or receiving of additional paths. The disable keyword cannot be used with the send or receive keyword.

Command Default

Additional path capability per neighbor is not configured.

Command Modes

Address family configuration (config-router-af)

Command History

Release

Modification

15.2(4)S

This command was introduced.

Cisco IOS XE Release 3.7S

This command was integrated into Cisco IOS XE Release 3.7S.

15.3(1)T

This command was integrated into Cisco IOS Release 15.3(1)T.

Usage Guidelines

Use this command to allow the negotiation of the BGP Additional Paths send and receive capabilities for a specific neighbor or peer group. The ability to send and receive additional paths is negotiated between two BGP neighbors during session establishment.

The bgp additional-paths {send [receive] | receive} command controls whether the local device can send or receive additional paths to and from all neighbors within an address family. If the neighbor additional-paths command is configured, its send and receive configurations for that neighbor or peer group override the configuration for the address family or for a template.

To override template or address family configurations that enable the sending or receiving of additional paths, use the neighbor additional-paths disable command.

To remove the per-neighbor or per-peer group configuration of the sending and receiving of additional paths, use the no neighbor additional-paths command. That neighbor will then follow the policy of a peer-template (if it belongs to one) or follow the address family additional path configuration for sending and receiving.

Examples

In the following example, additional paths can be sent and received for the specified neighbor:

router bgp 65000
 address-family ipv4 unicast
  neighbor 192.168.1.2 additional-paths send receive

In the following example, the no form of the command configures that additional paths cannot be sent for the specified neighbor. Because the receive capability was previously configured for that neighbor, the receive capability remains in effect. Note that the no neighbor 192.168.1.2 additional-paths send command does not NVGEN (it is not shown in the configuration file. The display would indicate "additional-paths receive".)

router bgp 65000
 address-family ipv4 unicast
  neighbor 192.168.1.2 additional-paths send receive
  no neighbor 192.168.1.2 additional-paths send

In the following example, additional paths can be sent and received for the address family, but the specified neighbor is disabled from sending or receiving additional paths:

router bgp 65000
 address-family ipv4 unicast
  bgp additional-paths send receive
  neighbor 192.168.4.6 additional-paths disable

In the following example, the send and receive capability of the neighbor overrides the receive-only capability of the address family:

router bgp 65000
 address-family ipv6 multicast
  bgp additional-paths receive
  bgp additional-paths select group-best
  neighbor 2001:DB8::1037 additional-paths send receive
  neighbor 2001:DB8::1037 advertise additional-paths group-best
!

Related Commands

Command

Description

additional-paths

Uses a policy template to configure BGP to send or receive additional paths.

advertise additional-paths

Advertises additional paths for a BGP peer policy template based on selection.

bgp additional-paths

Configures the send and receive capabilities of additional path information for the address family.

bgp additional-paths select (additional paths)

Selects the types of additional paths that are calculated and available as candidates for advertisement.

neighbor advertise additional-paths

Advertises additional paths for a neighbor based on selection.

neighbor advertise additional-paths

To advertise additional paths for a neighbor based on selection, use the neighbor advertise additional-paths command in address family configuration mode. To prevent the advertisement of additional paths for a neighbor based on selection, use the no form of the command.

neighbor { ip-address | ipv6-address | peer-group-name } advertise additional-paths [ best number ] [group-best] [all]

no neighbor { ip-address | ipv6-address | peer-group-name } advertise additional-paths [ best number ] [group-best] [all]

Syntax Description

ip-address

IP address of the neighbor for which to advertise additional paths.

ipv6-address

IPv6 address of the neighbor for which to advertise additional paths.

peer-group-name

Name of the peer group of peers for which to advertise additional paths.

best number

(Optional) Advertises the paths tagged with the best 2 or best 3 tag as the best paths.

  • The number value can be 2 or 3.

group-best

(Optional) Advertises the paths tagged with the group-best tag.

all

(Optional) Advertises the paths tagged with the all tag.

Command Default

Additional paths are not advertised for a neighbor.

Command Modes

Address family configuration (config-router-af)

Command History

Release

Modification

15.2(4)S

This command was introduced.

Cisco IOS XE Release 3.7S

This command was integrated into Cisco IOS XE Release 3.7S.

15.3(1)T

This command was integrated into Cisco IOS Release 15.3(1)T.

Usage Guidelines

Use this command to specify the neighbor for which additional paths are advertised. You can advertise additional paths based on any combination of the selection methods, but you must choose at least one selection method if you use this command. Otherwise, only the bestpath is advertised.

Examples

In the following example, for every address family, there are one or more eBGP neighbors not shown in the configuration that are sending routes to the local device. The eBGP routes learned from these neighbors are advertised toward the neighbors shown in the configuration, and the path attributes are changed. The example configures that:

  • The route map called add_path1 specifies that all the paths are advertised toward neighbor 192.168.101.15, but any path that is marked with the best 2 tag will have its metric set to 780 before being sent toward that neighbor.

  • The route map called add_path2 specifies that any path that is marked with best 3 will have its metric set to 640 and will be advertised toward neighbor 192.168.101.25.

  • The route map called add_path3 specifies that any path that is marked with group-best will have its metric set to 825 and will be advertised toward neighbor 2001:DB8::1045.

  • In the IPv6 multicast address family, all paths are candidates to be advertised and will be advertised toward neighbor 2001:DB8::1037.

router bgp 1
 neighbor 192.168.101.15 remote-as 1
 neighbor 192.168.101.25 remote-as 1
 neighbor fec0::1045 remote-as 1
 neighbor fec0::1037 remote-as 1
!
 address-family ipv4 unicast
  bgp additional-paths send receive
  bgp additional-paths select all best 3 group-best
  neighbor 192.168.101.15 activate
  neighbor 192.168.101.15 route-map add_path1 out
  neighbor 192.168.101.15 advertise additional-paths best 2
  exit-address-family 
!
address-family ipv4 multicast
  bgp additional-paths send receive
  bgp additional-paths select all best 3 group-best
  neighbor 192.168.101.25 activate
  neighbor 192.168.101.25 route-map add_path2 out
  neighbor 192.168.101.25 advertise additional-paths best 3
  exit-address-family 
!
 address-family ipv6 unicast
  bgp additional-paths send receive
  bgp additional-paths select group-best
  neighbor 2001:DB8::1045 activate
  neighbor 2001:DB8::1045 route-map add_path3 out
  neighbor 2001:DB8::1045 advertise additional-paths group-best 
  exit-address-family
!
 address-family ipv6 multicast
  bgp additional-paths send receive
  bgp additional-paths select all
  neighbor 2001:DB8::1037 activate
  neighbor 2001:DB8::1037 advertise additional-paths all 
  exit-address-family
!
route-map add_path1 permit 10
 match additional-paths advertise-set best 2
 set metric 780
route-map add_path1 permit 20
!
route-map add_path2 permit 10
 match additional-paths advertise-set best 3
 set metric 640
!
route-map add_path3 permit 10
 match additional-paths advertise-set group-best
 set metric 825
!
      

Related Commands

Command

Description

additional-paths

Uses a policy template to configure BGP to send or receive additional paths.

advertise additional-paths

Advertises additional paths for a BGP peer policy template based on selection.

bgp additional-paths

Configures the send and receive capabilities of additional path information for the address family.

bgp additional-paths select (additional paths)

Specifies the selection methods for calculating additional paths.

neighbor additional-paths

Negotiates the send and receive capability of additional paths per neighbor.

neighbor advertise best-external

To specify that a neighbor receive the advertisement of the best external path, use the neighbor advertise best-external command in address family configuration mode. To remove the designation, use the no form of this command.

neighbor { ip-address | ipv6-address | peer-group-name | policy-template-name } advertise best-external

no neighbor { ip-address | ipv6-address | peer-group-name | policy-template-name } advertise best-external

Syntax Description

ip-address

Advertises the best external path to this IPv4 neighbor.

ipv6-address

Advertises the best external path to this IPv6 neighbor.

peer-group-name

Advertises the best external path to this peer group.

policy-template-name

Advertises the best external path to neighbors described by the policy template.

Command Default

This command is disabled by default; the Border Gateway Protocol (BGP) best path is advertised to neighbors.

Command Modes

Address family configuration (config-router-af)

Command History

Release

Modification

Cisco IOS XE Release 3.4S

This command was introduced.

15.2(3)T

This command was integrated into Cisco IOS Release 15.2(3)T.

15.2(4)S

This command was integrated into Cisco IOS Release 15.2(4)S.

Usage Guidelines

By default, the BGP best path is advertised to a peer. However, if the BGP Diverse Path feature is configured, you can use this command to specify that the best external path is advertised to the peer also.

This command does not enable the BGP Best External feature or the BGP Diverse Path feature. The bgp additional-paths select best-external command must be configured before the neighbor advertise best-external command can be configured. If the neighbor advertise best-external command is configured, but the bgp additional-paths select best-external command is not configured, an error message is generated.

This command can be configured for nonclient Internal Border Gateway Protocol (IBGP) peers only. It can be configured at the PE, ASBR, or route reflector. When it is configured at a route reflector, the best-external functionality is inter-cluster, best-external functionality.

When the neighbor advertise best-external command is configured:

  • At the PE:
    • If the bgp additional-paths select best-external command (the new style command) is used to calculate the best external path, the best external path is advertised.
    • If the bgp advertise-best-external command (the old style command) is already present, the neighbor advertise best-external command cannot be configured and an error message is generated.
  • At the route reflector:
    • The route reflector advertises the best internal path to nonclient IBGP peers only when the overall best path is a path learned from another cluster.

This command cannot be configured on a route reflector toward its clients; it can be configured only for nonclient route reflectors.

Examples

In the following example, the neighbor at 10.1.1.1 is configured to receive the advertisement of the best-external path:

router bgp 1
 neighbor 10.1.1.1 remote-as 1
 address-family ipv4 unicast
 neighbor 10.1.1.1 activate
 maximum-paths ibgp 4
 bgp bestpath igp-metric ignore
 bgp additional-paths select best-external
 bgp additional-paths install
 neighbor 10.1.1.1 advertise best-external

Related Commands

Command

Description

bgp additional-paths select best-external

Specifies that the system calculate a second BGP best path among those received from external neighbors.

bgp advertise-best-external

Enables BGP to calculate an external route as the best backup path for a given address family, to install it into the RIB and Cisco Express Forwarding, and to advertise the best external path to its neighbors.

bgp bestpath igp-metric ignore

Specifies that the system ignore the IGP metric during best path selection.

maximum-paths ebgp

Configures multipath load sharing for EBGP and IBGP routes.

maximum-paths ibgp

Controls the maximum number of parallel IBGP routes that can be installed in a routing table.

neighbor advertise diverse-path

To specify that an additional path (a backup path or multipath or both) is advertised to a peer in addition to the best path, use the neighbor advertise diverse-path command in address family configuration mode. To remove the designation, use the no form of this command.

neighbor { ip-address | ipv6-address | peer-group-name | policy-template-name } advertise diverse-path { backup [mpath] | mpath }

no neighbor { ip-address | ipv6-address | peer-group-name | policy-template-name } advertise diverse-path { backup [mpath] | mpath }

Syntax Description

ip-address

Advertises a diverse path to this IPv4 neighbor.

ipv6-address

Advertises a diverse path to this IPv6 neighbor.

peer-group-name

Advertises a diverse path to this peer group.

policy-template-name

Advertises a diverse path to neighbors described by the policy template?

backup

(Optional) Advertises the backup path. If backup is specified, but there is no backup path, the best path is advertised.

mpath

(Optional) Advertises the multipath, which is the second best path. If mpath is specified, but there is no multipath, the best path is advertised. If both backup and mpath are specified, the multipath is advertised.

Command Default

This command is disabled by default; the Border Gateway Protocol (BGP) best path is advertised to neighbors.

Command Modes

Address family configuration (config-router-af)

Command History

Release

Modification

Cisco IOS XE Release 3.4S

This command was introduced.

15.2(3)T

This command was integrated into Cisco IOS Release 15.2(3)T.

15.2(4)S

This command was integrated into Cisco IOS Release 15.2(4)S.

Usage Guidelines

By default, the BGP best path is advertised to a peer. However, if the BGP Diverse Path feature is configured, you can use this command to specify that the backup path or multipath (or both) is advertised to the peer also. This command is not supported for VRFs.

This command does not enable the BGP Diverse Path feature. If this command is configured, but the BGP Diverse Path feature is not configured (by one of the commands in the Related Commands table), a warning message is generated.

If any of the Related Commands is configured, but there is no multipath or backup path (no additional path), then the specified neighbor will receive the best path in advertisements.

Neighbors for which this command is not specified will receive the best path in advertisements.

This command can be configured for route reflector clients only (because the BGP Diverse Path feature applies within an autonomous system (AS) and within a single cluster).

If the bgp additional-paths select backup command was configured and is subsequently removed from the configuration before the neighbor advertise diverse-path backup command is removed, then the specified neighbor will receive the best path in advertisements.


Note


If the old style command for BGP PIC or Best External is already configured (bgp additional-paths install or bgp advertise-best-external), the neighbor advertise diverse-path command cannot be configured; an error message is generated.


Either the backup keyword or the mpath keyword is required; both keywords can be specified.

Examples

In the following example, the neighbor at 10.1.1.1 will receive an advertisement for a backup path in addition to the bestpath:

router bgp 1
 neighbor 10.1.1.1 remote-as 1
 address-family ipv4 unicast
 neighbor 10.1.1.1 activate
 maximum-paths ibgp 4
 bgp bestpath igp-metric ignore
 bgp additional-paths select backup
 bgp additional-paths install
 neighbor 10.1.1.1 advertise diverse-path backup

Related Commands

Command

Description

bgp additional-paths install

Enables BGP to calculate a backup path for a given address and to install it into the RIB and CEF.

bgp additional-paths select backup

Specifies that the system calculate a second BGP best path as a backup path.

maximum-paths ebgp

Configures multipath load sharing for EBGP and IBGP routes.

maximum-paths ibgp

Controls the maximum number of parallel IBGP routes that can be installed in a routing table.

neighbor advertise-map

To advertise the routes in the BGP table matching the configured route-map, use the neighbor advertise-map command in router configuration mode. To disable route advertisement, use the no form of this command.

neighbor { ipv4-address | ipv6-address } advertise-map map-name { exist-map map-name | non-exist-map map-name } [ check-all-paths ]

no neighbor { ipv4-address | ipv6-address } advertise-map map-name { exist-map map-name | non-exist-map map-name } [ check-all-paths ]

Syntax Description

ip-address

Specifies the IPv4 address of the router that should receive conditional advertisements.

ipv6-address

Specifies the IPv6 address of the router that should receive conditional advertisements.

advertise-map map-name

Specifies the name of the route map that will be advertised if the conditions of the exist map or non-exist map are met.

exist-map map-name

Specifies the name of the exist-map that is compared with the routes in the BGP table to determine whether the advertise-map route is advertised or not.

non-exist-map map-name

Specifies the name of the non-exist-map that is compared with the routes in the BGP table to determine whether the advertise-map route is advertised or not.

check-all-paths

(Optional) Enables checking of all paths by the exist-map with a prefix in the BGP table.

Command Default

No default behavior or values.

Command Modes

Router configuration (config-router)

Command History

Release

Modification

11.1CC

This command was introduced.

11.2

This command was integrated into Cisco IOS Release 11.2.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

15.3(2)S

This command was integrated into Cisco IOS Release 15.3(2)S.

Cisco IOS XE Release 3.9S

This command was integrated into Cisco IOS XE Release 3.9S.

15.0(02)SG

This command was integrated into Cisco IOS Release 15.0(02)SG. The check-all-paths keyword was introduced.

Usage Guidelines

Use the neighbor advertise-map command to conditionally advertise selected routes. The routes (prefixes) that will be conditionally advertised are defined in two route maps: an advertise map and either an exist map or non-exist map.

  • The route map associated with the exist map or non-exist map specifies the prefix that the BGP speaker will track.
  • The route map associated with the advertise map specifies the prefix that will be advertised to the specified neighbor when the condition is met.

If an exist map is configured, the condition is met when the prefix exists in both the advertise map and the exist map.

If a non-exist map is configured, the condition is met when the prefix exists in the advertise map, but does not exist in the non-exist map.

If the condition is not met, the route is withdrawn and conditional advertisement does not occur. All routes that may be dynamically advertised or not advertised need to exist in the BGP routing table for conditional advertisement to occur.

Examples

The following router configuration example configures BGP to check all

router bgp 5
address-family ipv4 unicast
neighbor 10.2.1.1 advertise-map MAP1 exist-map MAP2

The following address family configuration example configures BGP to conditionally advertise a prefix to the 10.1.1.1 neighbor using a non-exist map. If the prefix exists in MAP3 but not MAP4, the condition is met and the prefix is advertised.

router bgp 5
address-family ipv4 unicast
neighbor 10.1.1.1 advertise-map MAP3 non-exist-map MAP4

The following peer group configuration example configures BGP to check all paths against the prefix to the BGP neighbor:

router bgp 5
address-family ipv4
redistribute static
neighbor route1 send-community both
neighbor route1 advertise-map MAP1 exist-map MAP2 check-all-paths

The following is sample output from the show ip bgp command where all paths are checked in the BGP table:

Device# show ip bgp

BGP table version is 12, local router ID is 192.168.10.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 0.0.0.0          0.0.0.0                  0         32768 i
*> 1.0.0.0/32       0.0.0.0                  0         32768 ?
*> 192.168.10.1/8   0.0.0.0                  0         32768 i
r> 192.168.20.1/8  	192.168.20.2             0  			  0 65200 1 2 3 4 5 ?
r> 192.168.30.1/8 	 192.168.30.2             0       0 65200 ?
*  192.168.50.1   	 192.168.20.2             0       0 65200 1 2 3 4 5 ?
*>                  192.168.30.2             0       0 65200 ?

The following is sample output from the show ip bgp advertised-routes command to check the routes advertised for the BGP neighbors.

Device# show ip bgp neighbors 192.168.20.2 advertised-routes

BGP table version is 12, local router ID is 192.168.10.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

			Network          Next Hop            Metric LocPrf Weight Path
*> 0.0.0.0          0.0.0.0                  0         32768 i 
*> 167.84.96.5/32   0.0.0.0                  0         32768 i

Total number of prefixes 2 

Note


In the example above, 0.0.0.0 is the default network path that is advertised for the BGP neighbor 192.168.20.2.

The following debug logs indicate the prefix that matches the advertised exist-map after checking all paths from the BGP table.

*Sep 26 23:13:00.723: BGP(0): 192.168.20.2 0.0.0.0/0 matches advertise map MAP1,
state: Advertise

Related Commands

Command

Description

address-family ipv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPNv4 address prefixes.

address-family ipv6

Places router in address family configuration mode for configuring routing sessions, such as BGP, that use standard IPv6 address prefixes

route-map

Defines the conditions for redistributing routes from one routing protocol into another, or enables policy routing.

neighbor advertisement-interval

To set the minimum route advertisement interval (MRAI) between the sending of BGP routing updates, use the neighbor advertisement-interval command in address family or router configuration mode. To restore the default value, use the no form of this command.

neighbor { ip-address | peer-group-name } advertisement-interval seconds

no neighbor { ip-address | peer-group-name } advertisement-interval seconds

Syntax Description

ip-address

IP address of the neighbor.

peer-group-name

Name of a BGP peer group.

seconds

Time (in seconds) is specified by an integer ranging from 0 to 600.

Command Default

eBGP sessions not in a VRF: 30 seconds

eBGP sessions in a VRF: 0 seconds

iBGP sessions: 0 seconds

Command Modes


Router configuration (config-router)

Command History

Release

Modification

10.3

This command was introduced.

12.0(7)T

Address family configuration mode was added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

12.4T, 12.2SB, 12.2SE, 12.2SG, 12.2SR, 12.2SX, Cisco IOS XE 2.1

This command was modified. The default value for eBGP sessions in a VRF and for iBGP sessions changed from .5 seconds to 0 seconds.

Usage Guidelines

When the MRAI is equal to 0 seconds, BGP routing updates are sent as soon as the BGP routing table changes.

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

Examples

The following router configuration mode example sets the minimum time between sending BGP routing updates to 10 seconds:

router bgp 5
 neighbor 10.4.4.4 advertisement-interval 10

The following address family configuration mode example sets the minimum time between sending BGP routing updates to 10 seconds:

router bgp 5
address-family ipv4 unicast
 neighbor 10.4.4.4 advertisement-interval 10

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPNv4 address prefixes.

neighbor peer-group (creating)

Creates a BGP peer group.

neighbor aigp send cost-community

To convert the accumulated interior gateway protocol (AIGP) to the cost community on the send side, use the neighbor aigp send cost-community command in address family configuration mode. To disable this functionality, use the no form of this command.

neighbor { ip-address | ipv6-address | tag-name } aigp send cost-community community-id poi { igp-cost | pre-bestpath } [transitive]

no neighbor { ip-address | ipv6-address | tag-name } aigp send cost-community community-id poi { igp-cost | pre-bestpath } [transitive]

Syntax Description

ip-address

IPv4 address of the neighbor.

ipv6-address

IPv6 address of the neighbor.

tag-name

Name of a Border Gateway Protocol (BGP) peer group.

community-id

Cost extended community ID that carries the AIGP value. The range is from 0 to 255.

poi

Specifies the point of insertion.

igp-cost

Specifies the point of insertion after the interior gateway protocol (IGP).

pre-bestpath

Specifies the point of insertion at the beginning of the bestpath.

transitive

(Optional) Specifies that the cost community is transitive.

Command Default

AIGP attribute processing is enabled.

Command Modes

Address family configuration (config-router-af)

Command History

Release

Modification

Cisco IOS XE Release 3.12S

This command was introduced.

15.4(2)S

This command was integrated into Cisco IOS Release 15.4(2)S.

Usage Guidelines

Using the neighbor aigp send cost-community command, BGP translates the attributes that cannot understand the AIGP attribute to the cost community and attaches them to the route before advertising to legacy provider edge (PE) devices.

This command is supported in the following address families:
  • IPv4 unicast

  • IPv4 multicast

  • IPv6 unicast

  • IPv6 multicast

Examples

In the following example, the device belongs to autonomous system 65000 and is configured to send the cost-community attribute to its neighbor at IP address 172.16.70.23:

Device# configure terminal
Device(config)# router bgp 65000
Device(config-router)# address-family ipv4 multicast
Device(config-router-af)# neighbor 172.16.70.23 aigp send cost-community 100 poi igp-cost transitive
Device(config-router-af)# exit

Related Commands

Command

Description

aigp

Enables sending and receiving of the AIGP attribute per eBGP and iBGP neighbors.

neighbor aigp send med

Converts AIGP to the multi-exit discriminator (MED) on the send side.

neighbor aigp send med

To convert the accumulated interior gateway protocol (AIGP) to multi-exit discriminator (MED) on the send side, use the neighbor aigp send med command in address family configuration mode. To disable this functionality, use the no form of this command.

neighbor { ip-address | ipv6-address | tag-name } aigp send med

no neighbor { ip-address | ipv6-address | tag-name } aigp send med

Syntax Description

ip-address

IPv4 address of the neighbor.

ipv6-address

IPv6 address of the neighbor.

tag-name

Name of a Border Gateway Protocol (BGP) peer group.

Command Default

AIGP attribute processing is enabled.

Command Modes

Address family configuration (config-router-af)

Command History

Release

Modification

Cisco IOS XE Release 3.12S

This command was introduced.

15.4(2)S

This command was integrated into Cisco IOS Release 15.4(2)S.

Usage Guidelines

Using the neighbor aigp send med command, BGP translates the attributes that cannot understand the AIGP attribute to MED and attaches them to the route before advertising to legacy provider edge (PE) devices.

This command is supported in the following address families:
  • IPv4 unicast

  • IPv4 multicast

  • IPv6 unicast

  • IPv6 multicast

Examples

In the following example, the device belongs to autonomous system 65000 and is configured to send the MED attribute to its neighbor at IP address 172.16.70.23:

Device# configure terminal
Device(config)# router bgp 65000
Device(config-router)# address-family ipv4 multicast
Device(config-router-af)# neighbor 172.16.70.23 aigp send med
Device(config-router-af)# exit

Related Commands

Command

Description

aigp

Enables sending and receiving of the AIGP attribute per eBGP and iBGP neighbors.

neighbor aigp send cost-community

Converts AIGP to the cost community on the send side.

neighbor allow-policy

To allow a route reflector to be configured to change iBGP attributes (policies) in updates for an iBGP session that has the iBGP Local-AS feature configured, use the neighbor allow-policy command in router or address family configuration mode. To disable the functionality, use the no form of this command.

neighbor { ip-address | ipv6-address | peer-group } allow-policy

no neighbor { ip-address | ipv6-address | peer-group } allow-policy

Syntax Description

ip-address

IPv4 address of the iBGP neighbor.

ipv6-address

IPv6 address of the iBGP neighbor.

peer-group

Name of a BGP peer group.

Command Default

A route reflector does not change iBGP policies in updates.

Command Modes

Router configuration (config-router)

Address family configuration (config-router-af)

Command History

Release

Modification

15.3(2)S

This command was introduced.

Cisco IOS XE Release 3.9S

This command was integrated into Cisco IOS XE Release 3.9S.

Usage Guidelines

This command is intended to be used when migrating or merging autonomous systems. Typically, a route reflector (RR) would not change iBGP attributes in updates to a peer. In a scenario where a network administrator is merging autonomous systems, the neighbor allow-policy command provides flexibility by allowing the administrator to configure the route reflector to change iBGP policies (by configuring a route map). The RR would have the neighbor remote-as command and the neighbor local-as command specify the same AS, thus enabling the iBGP Local-AS feature.

This command can be used in iPv4, IPv6, VPNv4, or VPNv6 address family configuration mode.

Examples

The following example configures a route reflector in AS 4000 to treat BGP sessions with the neighbor in AS 2500 as iBGP sessions. That is, iBGP attributes (LOCAL_PREF, ORIGINATOR_ID, CLUSTER_ID, and CLUSTER_LIST) will not be dropped from routes in advertisements to and from the neighbor; the attributes will be preserved. AS 2500 will be prepended to the AS_PATH attribute in all routes to and from the neighbor. Additionally, the neighbor allow-policy command enables the RR to be configured with a route map that changes iBGP policies.

router bgp 4000 
 neighbor 192.168.1.1 remote-as 2500
 neighbor 192.168.1.1 local-as 2500
 neighbor 192.168.1.1 route-reflector-client
 address-family vpnv4
  neighbor 192.168.1.1 allow-policy
! 
 address-family vpnv6
  neighbor 192.168.1.1 allow-policy

Related Commands

Command

Description

neighbor local-as

Customizes the AS_PATH attribute for routes received from an eBGP neighbor or enables the iBGP Local-AS feature.

neighbor remote-as

Adds an entry to the BGP or multiprotocol BGP neighbor table.

show ip bgp vpnv4 all neighbors

Displays information about VPNv4 sessions.

show ip bgp vpnv4 all update-group

Displays information about VPNv4 update groups.

neighbor announce rpki state

To cause the device to send the Resource Public Key Infrastructure (RPKI) state with prefixes to its Internal Border Gateway Protocol (iBGP) neighbor in the Border Gateway Protocol (BGP) extended community attribute, and to also receive the RPKI state with prefixes from that neighbor, use the neighbor announce rpki state command in router configuration mode or IPv4 unicast or IPv6 unicast address family configuration mode. To stop the device from sending and receiving the RPKI state, use the no form of this command.

neighbor { ipv4-address | ipv6-address } announce rpki state

no neighbor { ipv4-address | ipv6-address } announce rpki state

Syntax Description

ipv4-address

IPv4 address of the iBGP neighbor that will receive the prefixes and associated RPKI state, and from which the device will receive prefixes and the associated RPKI state.

ipv6-address

IPv6 address of the iBGP neighbor that will receive the prefixes and associated RPKI state, and from which the device will receive prefixes and the associated RPKI state.

Command Default

No RPKI state is announced to or received from iBGP neighbors.

Command Modes

Router configuration (config-router)

IPv4 unicast or IPv6 unicast address family configuration (config-router-af)

Command History

Release

Modification

XE 3.5S

This command was introduced.

15.2(1)S

This command was integrated into Cisco IOS Release 15.2(1)S.

15.2(4)S

This command was implemented on the Cisco 7200 series routers.

Usage Guidelines

Use this command for the device to send the RPKI state to a neighbor than it is to configure the neighbor with the BGP—Origin AS Validation feature. Thus, the neighbor is spared from having to connect to an RPKI server. This command works in both directions. That is, the specified neighbor can send and receive the RPKI state. If this command is not configured, the local device ignores the extended community attribute if the neighbor sends it.

The extended community attribute announced is 0x4300 0x0000 (four bytes indicating the RPKI state). The four bytes indicating the state will be treated as a 32-bit unsigned integer having one of the following values:

  • 0 indicating Valid

  • 1 indicating Not Found

  • 2 indicating Invalid

If this command is configured, upon receiving a route with the extended community attribute attached from an iBGP peer, the device assigns the route the corresponding validation state.


Note


If the neighbor announce rpki state command is not configured, all prefixes received from an iBGP peer will be marked as Valid, including the prefixes that must have marked as Not Found.


This attribute will not be sent to External Border Gateway Protocol (eBGP) neighbors, even if they are configured to allow sending of the attribute.

The following behaviors also apply to this command:

  • The neighbor announce rpki state command is possible only if the device is configured to send extended communities to that neighbor on that address family.

  • The neighbor announce rpki state command is completely independent of whether RPKI is configured for the address family.

  • Once the neighbor announce rpki state command or the bgp rpki server command is configured for an address family, the device starts doing RPKI validation for every path in that address family.

  • The enabling and disabling of the neighbor announce rpki state command causes neighbors to be split into their own update groups based on whether this portion of their configuration is identical.

  • If the neighbor announce rpki state command is not configured, the device will save the RPKI state received from other devices, but will only use it if at least one other neighbor in the address family is configured with the neighbor announce rpki state command or if the topology is otherwise enabled for the use of RPKI.

  • If the neighbor send-community extended or neighbor send-community both command is removed from the configuration, the neighbor announce rpki state configuration is also removed.

  • On route reflectors (RRs), networks that include an RPKI state extended community, but that come from neighbors for which the neighbor announce rpki state command is not configured, will be advertised to other RR clients, as long as those clients are capable of receiving an extended community.

  • If a network has an RPKI state extended community and is received by an RR from a neighbor for which the neighbor announce rpki state command is configured, then it will be reflected to all RR clients that are configured to accept extended communities, regardless of whether the neighbor announce rpki state command is configured for those other RR clients.

  • A neighbor announce rpki state command can be used in a peer policy template, and it is inherited.

  • If a neighbor announce rpki state command is used in a peer policy template, it must be in the same template as the send-community extended command. The neighbor announce rpki state command and the send-community extended command must come from the same template or be configured for the same neighbor.

Examples

The following example causes the device to send prefixes and the RPKI state to the specified neighbor and also to receive prefixes and the RPKI state from the neighbor:

router bgp 65000
 neighbor 192.168.2.2 remote-as 65000
 address-family ipv4 unicast
 neighbor 192.168.2.2 send-community extended
 neighbor 192.168.2.2 announce rpki state

Related Commands

Command

Description

bgp rpki server

Connects to an RPKI server and enables the validation of BGP prefixes based on the AS from which the prefix originates.

clear ip bgp rpki server

Closes the TCP connection to the specified RPKI server, purges SOVC records downloaded from that server, renegotiates the connection, and redownloads SOVC records.

show ip bgp rpki servers

Displays the current state of communication with RPKI servers.

show ip bgp rpki table

Displays the currently cached list of networks and associated AS numbers received from the RPKI server.

neighbor as-override split-horizon

To enable split-horizon for a neighbor in a virtual routing and forwarding (VRF) instance, use the neighbor as-override split-horizon command in router address family configuration mode. To disable split-horizon for a neighbor in a VRF instance, use the no form of the command.

neighbor ip-address as-override split-horizon

no neighbor ip-address as-override split-horizon

Syntax Description

ip-address

IP address of the neighbor.

as-override

Configures a provider edge (PE) device to override the autonomous system number (ASN) of a site with the ASN of a provider.

split-horizon

Maintains split-horizon while sending updates to neighbors.

Command Default

Split-horizon is not enabled for a neighbor in a virtual routing and forwarding (VRF) instance.

Command Modes

router-address-family configuration (config-router-af)

Command History

Release Modification

Cisco IOS XE Release 3.14S

This command was introduced.

Usage Guidelines

Use the neighbor as-override split-horizon command to group all the BGP neighbors into separate replication-groups, even when they are in the same update-group, and ensure that the route updates propagated from a Customer Edge (CE) device are not sent to the same CE device. This command enables a Provider Edge (PE) or CE device to selectively send and block updates to one or more neighboring PE or CE devices in the same update-group. The PE or CE device sends or blocks a message to a neighboring PE or CE device based on the type of the message and on whether the originator of the message matches the router ID of the PE or CE device.


Note


Configuring the site-of-origin (SoO) along with the BGP AS-Override Split-Horizon feature is not recommended.



Note


The device will reset the Border Gateway Protocol (BGP) session when you configure the neighbor as-override split-horizon command.


Examples

The following example shows how to enable split-horizon for a neighbor in a virtual routing and forwarding (VRF) instance:

Device> enable
Device# configure terminal
Device(config)# router bgp 21
Device(config-router)# address-family ipv4 vrf vrf1
Device(config-router-af)# neighbor 192.0.2.1 remote-as 1
Device(config-router-af)# neighbor 192.0.2.1 activate
Device(config-router-af)# neighbor 192.0.2.1 as-override split-horizon
Device(config-router-af)# neighbor 198.51.100.1 remote-as 1
Device(config-router-af)# neighbor 198.51.100.1 activate
Device(config-router-af)# neighbor 198.51.100.1 as-override split-horizon

Related Commands

Command

Description

neighbor activate

Enables the exchange of information with a BGP neighboring device.

neighbor remote-as

Allows a neighboring device's IP address to be included in the BGP routing table.

neighbor bmp-activate

To activate the BGP Monitoring Protocol (BMP) monitoring for a BGP neighbor, use the neighbor bmp-activate command in router configuration mode. To deactivate the BMP monitoring for a BGP neighbor, use the no form of this command.

neighbor { ipv4-addr | neighbor-tag | ipv6-addr } bmp-activate { all | server server-number-1 [ server server-number-2 ... [ server server-number-n ] ] }

no neighbor { ipv4-addr | neighbor-tag | ipv6-addr } bmp-activate

Syntax Description

ipv4-addr

Specifies the IPv4 address for each BGP neighbor.

neighbor-tag

Specifies a name or tag for each BGP neighbor.

ipv6-addr

Specifies the IPv6 address for each BGP neighbor.

all

Activates BMP monitoring on all BGP BMP servers.

server server-number-n

Activates BMP monitoring on a specific BGP BMP server. The value of n ranges from 1 to 4. You can randomly specify any server number to activate BMP monitoring on it. Optionally, you can activate BMP monitoring on the other servers after you configure the first one.

Command Default

BMP monitoring is not activated on the BMP servers for BGP BMP neighbors.

Command Modes

Router configuration (config-router)

Command History

Release Modification

15.4(1)S

This command was introduced.

Cisco IOS XE Release 3.11S

This command was integrated into Cisco IOS XE Release 3.11S.

Usage Guidelines

The neighbor bmp-activate command is only used to activate BMP monitoring on the BGP BMP servers for the BGP BMP neighbors. Only after you activate BMP monitoring, you can configure a BMP server and its parameters using the bmp command, which also enables the BMP server configuration commands to configure specific servers. Use the show ip bgp bmp command to display the configuration of the BMP servers and neighbors and the connectivity between them.

Examples

The following example shows how to activate BMP on a neighbor with IP address 10.1.1.1, which is monitored by BMP servers (in this case, server 1 and 2):

Device> enable
Device# configure terminal
Device(config)# router bgp 65000
Device(config-router)# neighbor 10.1.1.1 bmp-activate server 1 server 2
Device(config-router)# end

The following example shows how to configure initial refresh delay of 30 seconds for BGP neighbors on which BMP is activated using the neighbor bmp-activate command:

Device> enable
Device# configure terminal
Device(config)# router bgp 65000
Device(config-router)# bmp initial-refresh delay 30
Device(config-router)# end

The following is sample output from the show ip bgp bmp neighbors command, which shows the status of 10 peers configured for a BGP BMP neighbor monitored by BMP server 1 and 2:

Device# show ip bgp bmp server neighbors

Number of BMP neighbors configured: 10
BMP Refresh not in progress, refresh not scheduled
Initial Refresh Delay configured, refresh value 30s
BMP buffer size configured, buffer size 2048 MB, buffer size bytes used 0 MB

Neighbor           PriQ      MsgQ      CfgSvr#             ActSvr#             RM Sent
30.1.1.1           0         0         1  2                1  2                16      
2001:DB8::2001     0         0         1  2                1  2                15      
40.1.1.1           0         0         1  2                1  2                26      
2001:DB8::2002     0         0         1  2                1  2                15      
50.1.1.1           0         0         1  2                1  2                16      
60.1.1.1           0         0         1  2                1  2                26      
2001:DB8::2002     0         0         1                   1                   9       
70.1.1.1           0         0         2                   2                   12      
Neighbor           PriQ      MsgQ      CfgSvr#             ActSvr#             RM Sent
80.1.1.1           0         0         1                   1                   10      
2001:DB8::2002     0         0         1  2                1  2                16      

Related Commands

Command

Description

bmp

Configures BMP parameters on BGP BMP servers.

show ip bgp bmp

Displays information about BMP servers and neighbors.

neighbor capability orf prefix-list

To advertise outbound route filter (ORF) capabilities to a peer router, use the neighbor capability orf prefix-list command in address family or router configuration mode. To disable ORF capabilities, use the no form of this command.

neighbor ip-address capability orf prefix-list [ receive | send | both ]

no neighbor ip-address capability orf prefix-list [ receive | send | both ]

Syntax Description

ip-address

The IP address of the neighbor router.

receive

(Optional) Enables the ORF prefix list capability in receive mode.

send

(Optional) Enables the ORF prefix list capability in send mode.

both

(Optional) Enables the ORF prefix list capability in both receive and send modes.

Command Default

No ORF capabilities are advertised to a peer router.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.0(11)ST

This command was introduced.

12.2(4)T

This command was integrated into Cisco IOS Release 12.2(4)T.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

The neighbor capability orf prefix-list command is used to reduce the number of BGP prefixes that a BGP speaker sends or receives from a peer router based on prefix filtering.

In most configurations, this command will be used to advertise both send and receive ORF capabilities with the both keyword. However, this feature can be configured in one direction between two routers with one router configured to send ORF capabilities and another router configured to receive ORF capabilities from the first router.

Examples

The following examples configure routers to advertise ORF send or receive capabilities to BGP neighbors.

Examples

The following example creates an outbound route filter and configures Router-A (10.1.1.1) to advertise the filter to Router-B (172.16.1.2). An IP prefix list named FILTER is created to specify the 192.168.1.0/24 subnet for outbound route filtering. The ORF send capability is configured on Router-A so that Router-A can advertise the outbound route filter to Router-B.

ip prefix-list FILTER seq 10 permit 192.168.1.0/24 
!
router bgp 100
 address-family ipv4 unicast 
 neighbor 172.16.1.2 remote-as 200
 neighbor 172.16.1.2 ebgp-multihop 
 neighbor 172.16.1.2 capability orf prefix-list send
 neighbor 172.16.1.2 prefix-list FILTER in
 exit 

Examples

The following example configures Router-B to advertise the ORF receive capability to Router-A. Router-B will install the outbound route filter, defined in the FILTER prefix list, after ORF capabilities have been exchanged. An inbound soft reset is initiated on Router-B at the end of this configuration to activate the outbound route filter.

router bgp 200
 address-family ipv4 unicast 
 neighbor 10.1.1.1 remote-as 100
 neighbor 10.1.1.1 ebgp-multihop 255
 neighbor 10.1.1.1 capability orf prefix-list receive
 end 
clear ip bgp 10.1.1.1 in prefix-filter

Note


The inbound soft refresh must be initiated with the clear ip bgp command in order for the BGP ORF feature to function.


Related Commands

Command

Description

neighbor prefix-list

Distributes BGP neighbor information as specified in a prefix list.

neighbor cluster-id

To set the cluster ID of a client, use the neighbor cluster-id command in router configuration mode. To remove the cluster ID, use the no form of this command.

neighbor { ip-address | ipv6-address } cluster-id cluster-id

no neighbor { ip-address | ipv6-address } cluster-id cluster-id

Syntax Description

ip-address

IPv4 address of the BGP-speaking neighbor.

ipv6-address

IPv6 address of the BGP-speaking neighbor.

cluster-id

Cluster ID of this neighbor; maximum of 4 bytes.

  • The cluster ID can be in dotted decimal (such as 192.168.7.4) or decimal format (such as 23).

  • A cluster ID that is configured in decimal format (such as 23) will appear in a configuration file in dotted decimal format (such as 0.0.0.23). The decimal format does not appear in the configuration file.

Command Default

The local router ID of the route reflector is used as the cluster ID if no cluster ID is specified.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

Cisco IOS XE Release 3.8S

This command was introduced.

   

Usage Guidelines

This command is used on an IBGP neighbor (usually a route reflector) to configure cluster IDs on a per-neighbor basis. Configuring a cluster ID per neighbor allows the following functions:

  • The loop-prevention mechanism is modified such that when receiving a route, the RR discards the route if the RR's global cluster ID or any of the cluster IDs assigned to any of the clients is contained in the CLUSTER_LIST of the route.

  • The network administrator can disable client-to-client reflection on a per-neighbor basis if, for example, clients are fully meshed and hence there is no need to reflect the routes between them. (See the example below.)

If you change a cluster ID for a neighbor, BGP automatically does an inbound soft refresh and an outbound soft refresh for all iBGP peers.


Note


Even if cluster IDs are configured on a per-neighbor basis, the global cluster ID for the route reflector can still be configured as usual; use the bgp cluster-id command.


Examples

In the following example, the neighbor/client at 192.168.1.24 is configured with cluster ID 0.0.0.4:

router bgp 60000
 neighbor 192.168.1.24 cluster-id 0.0.0.4

In the following example, intracluster client-to-client route reflection is disabled for the cluster that has cluster ID 0.0.0.5:

router bgp 60000
 neighbor 192.168.1.24 cluster-id 192.168.0.115
 no bgp client-to-client reflection intra-cluster cluster-id 0.0.0.5

Related Commands

Command

Description

bgp client-to-client reflection intra-cluster

Enables or restores intra-cluster client-to-client route reflection to clients for the specified clusters.

bgp cluster-id

Sets the global cluster ID on a route reflector for a route reflector cluster.

neighbor route-reflector-client

Configures the router as a BGP route reflector and configures the specified neighbor as its client.

show ip bgp cluster-ids

Displays cluster IDs, how many neighbors are in each cluster, and whether client-to-client route reflection is disabled for each cluster.

show ip bgp neighbor

Displays the cluster ID of the neighbor.

show ip bgp template peer-session

Displays the cluster ID assigned to the template.

show ip bgp update-group

Displays the cluster ID assigned to the update group.

neighbor default-originate

To allow a BGP speaker (the local router) to send the default route 0.0.0.0 to a neighbor for use as a default route, use the neighbor default-originate command in address family or router configuration mode. To send no route as a default, use the no form of this command.

neighbor { ip-address | peer-group-name } default-originate [ route-map map-name ]

no neighbor { ip-address | peer-group-name } default-originate [ route-map map-name ]

Syntax Description

ip-address

IP address of the neighbor.

peer-group-name

Name of a BGP peer group.

route-map map-name

(Optional) Name of the route map. The route map allows route 0.0.0.0 to be injected conditionally.

Command Default

No default route is sent to the neighbor.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

11.0

This command was introduced.

12.0

Modifications were added to permit extended access lists.

12.0(7)T

Address family configuration mode was added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

This command does not require the presence of 0.0.0.0 in the local router. When used with a route map, the default route 0.0.0.0 is injected if the route map contains a match ip address clause and there is a route that matches the IP access list exactly. The route map can contain other match clauses also.

You can use standard or extended access lists with the neighbor default-originate command.

Examples

In the following router configuration example, the local router injects route 0.0.0.0 to the neighbor 172.16.2.3 unconditionally:

router bgp 109
 network 172.16.0.0
 neighbor 172.16.2.3 remote-as 200
 neighbor 172.16.2.3 default-originate

In the following example, the local router injects route 0.0.0.0 to the neighbor 172.16.2.3 only if there is a route to 192.168.68.0 (that is, if a route with any mask exists, such as 255.255.255.0 or 255.255.0.0):

router bgp 109
 network 172.16.0.0
 neighbor 172.16.2.3 remote-as 200
 neighbor 172.16.2.3 default-originate route-map default-map
!
route-map default-map 10 permit
 match ip address 1
!
access-list 1 permit 192.168.68.0

In the following example, the last line of the configuration has been changed to show the use of an extended access list. The local router injects route 0.0.0.0 to the neighbor 172.16.2.3 only if there is a route to 192.168.68.0 with a mask of 255.255.0.0:

router bgp 109
 network 172.16.0.0
 neighbor 172.16.2.3 remote-as 200
 neighbor 172.16.2.3 default-originate route-map default-map
!
route-map default-map 10 permit
 match ip address 100
!
access-list 100 permit ip host 192.168.68.0 host 255.255.0.0

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPNv4 address prefixes.

neighbor ebgp-multihop

Accepts and attempts BGP connections to external peers residing on networks that are not directly connected.

neighbor description

To associate a description with a neighbor, use the neighbor description command in router configuration mode or address family configuration mode. To remove the description, use the no form of this command.

neighbor { ip-address | peer-group-name } description text

no neighbor { ip-address | peer-group-name } description [text]

Syntax Description

ip-address

IP address of the neighbor.

peer-group-name

Name of an EIGRP peer group. This argument is not available in address-family configuration mode.

text

Text (up to 80 characters in length) that describes the neighbor.

Command Default

There is no description of the neighbor.

Command Modes

Router configuration (config-router) Address family configuration (config-router-af)

Command History

Release

Modification

11.3

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

15.0(1)M

This command was modified. Address-family configuration mode was added.

12.2(33)SRE

This command was integrated into Cisco IOS Release 12.2(33)SRE.

Cisco IOS XE Release 2.6

This command was integrated into Cisco IOS XE Release 2.6.

Examples

In the following examples, the description of the neighbor is “peer with example.com”:

Router(config)# router bgp 109
Router(config-router)# network 172.16.0.0
Router(config-router)# neighbor 172.16.2.3 description peer with example.com

In the following example, the description of the address family neighbor is “address-family-peer”:

Router(config)# router eigrp virtual-name
Router(config-router)# address-family ipv4 autonomous-system 4453
Router(config-router-af)# 
network 172.16.0.0
Router(config-router-af)# 
neighbor 172.16.2.3 description address-family-peer

Related Commands

Command

Description

address-family (EIGRP)

Enters address family configuration mode to configure an EIGRP routing instance.

network (EIGRP)

Specifies the network for an EIGRP routing process.

router eigrp

Configures the EIGRP address family process.

neighbor disable-connected-check

To disable connection verification to establish an eBGP peering session with a single-hop peer that uses a loopback interface, use the neighbor disable-connected-check command in address family or router configuration mode. To enable connection verification for eBGP peering sessions, use the no form of this command.

neighbor { ip-address | peer-group-name } disable-connected-check

no neighbor { ip-address | peer-group-name } disable-connected-check

Syntax Description

ip-address

IP address of a neighbor.

peer-group-name

Name of a BGP peer group.

Command Default

A BGP routing process will verify the connection of single-hop eBGP peering session (TTL=254) to determine if the eBGP peer is directly connected to the same network segment by default. If the peer is not directly connected to same network segment, connection verification will prevent the peering session from being established.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.0(22)S

This command was introduced.

12.2(13)T

This command was integrated into Cisco IOS Release 12.2(13)T.

Usage Guidelines

The neighbor disable-connected-check command is used to disable the connection verification process for eBGP peering sessions that are reachable by a single hop but are configured on a loopback interface or otherwise configured with a non-directly connected IP address.

This command is required only when the neighbor ebgp-multihop command is configured with a TTL value of 1. The address of the single-hop eBGP peer must be reachable. The neighbor update-source command must be configured to allow the BGP routing process to use the loopback interface for the peering session.

Examples

In the following example, a single-hop eBGP peering session is configured between two BGP peers that are reachable on the same network segment through a local loopback interfaces on each router:

Examples

Router(config)# interface loopback 1 
Router(config-if)# ip address 10.0.0.100 255.255.255
 
Router(config-if)# exit
 
Router(config)# router bgp 64512
 
Router(config-router)# neighbor 192.168.0.200 remote-as 65534
 
Router(config-router)# neighbor 192.168.0.200 ebgp-multihop 1
 
Router(config-router)# neighbor 192.168.0.200 update-source loopback 2
 
Router(config-router)# neighbor 192.168.0.200 disable-connected-check
Router(config-router)# end 

Examples

Router(config)# interface loopback 2
 
Router(config-if)# ip address 192.168.0.200 255.255.255
 
Router(config-if)# exit
 
Router(config)# router bgp 65534 
Router(config-router)# neighbor 10.0.0.100 remote-as 64512
 
Router(config-router)# neighbor 10.0.0.100 ebgp-multihop 1
 
Router(config-router)# neighbor 10.0.0.100 update-source loopback 1
 
Router(config-router)# neighbor 10.0.0.100 disable-connected-check
Router(config-router)# end
 

Related Commands

Command

Description

neighbor ebgp-multihop

Accepts or initiates BGP connections to external peers residing on networks that are not directly connected.

neighbor update-source

Configures Cisco IOS software to allow BGP sessions to use any operational interface for TCP connections.

neighbor distribute-list

To distribute BGP neighbor information as specified in an access list, use the neighbor distribute-list command in address family or router configuration mode. To remove an entry, use the no form of this command.

neighbor { ip-address | peer-group-name } distribute-list { access-list-number | expanded-list-number | access-list-name | prefix-list-name } { in | out }

no neighbor { ip-address | peer-group-name } distribute-list { access-list-number | expanded-list-number | access-list-name | prefix-list-name } { in | out }

Syntax Description

ip-address

IP address of the neighbor.

peer-group-name

Name of a BGP peer group.

access-list-number

Number of a standard or extended access list. The range of a standard access list number is from 1 to 99. The range of an extended access list number is from 100 to 199.

expanded-list-number

Number of an expanded access list number. The range of an expanded access list is from 1300 to 2699.

access-list-name

Name of a standard or extended access list.

prefix-list-name

Name of a BGP prefix list.

in

Access list is applied to incoming advertisements to that neighbor.

out

Access list is applied to outgoing advertisements to that neighbor.

Command Default

No BGP neighbor is specified.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

11.0

The peer-group-name argument was added.

11.2

The access-list-name argument was added.

12.0

The prefix-list-name argument was added.

12.0(7)T

Address family configuration mode was added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command. Specifying the command for a neighbor overrides the inbound policy that is inherited from the peer group.

Using a distribute list is one of several ways to filter advertisements. Advertisements can also be filtered by using the following methods:

  • Autonomous system path filters can be configured with the ip as-path access-list and neighbor filter-list commands.

  • The access-list (IP standard) and access-list (IP extended) commands can be used to configure standard and extended access lists for the filtering of advertisement.

  • The route-map (IP) command can be used to filter advertisements. Route maps may be configured with autonomous system filters, prefix filters, access lists and distribute lists.

Standard access lists may be used to filter routing updates. However, in the case of route filtering when using classless interdomain routing (CIDR), standard access lists do not provide the level of granularity that is necessary to configure advanced filtering of network addresses and masks. Extended access lists, configured with the access-list (IP extended)command, should be used to configure route filtering when using CIDR because extended access lists allow the network operator to use wild card bits to filter the relevant prefixes and masks. Wild card bits are similar to the bit masks that are used with normal access lists; prefix and mask bits that correspond to wild card bits that are set to 0 are used in the comparison of addresses or prefixes and wild card bits that are set to 1 are ignored during any comparisons. This function of extended access list configuration can also be used to filter addresses or prefixes based on the prefix length.


Note


Do not apply both a neighbor distribute-list and a neighbor prefix-list command to a neighbor in any given direction (inbound or outbound). These two commands are mutually exclusive, and only one command (neighbor prefix-list or neighbor distribute-list) can be applied to each inbound or outbound direction.


Examples

The following router configuration mode example applies list 39 to incoming advertisements from neighbor172.16.4.1. List 39 permits the advertisement of network 10.109.0.0.

router bgp 109 
 network 10.108.0.0 
 neighbor 172.16.4.1 distribute-list 39 in 

The following three examples show different scenarios for using an extended access list with a distribute list. The three examples are labeled “Example A”, “Example B”, and “Example C.” Each of the example extended access list configurations are used with the neighbor distribute-list command configuration example below.

router bgp 109 
 network 10.108.0.0
 neighbor 172.16.4.1 distribute-list 101 in 

Examples

The following extended access list example will permit route 192.168.0.0 255.255.0.0 but deny any more specific routes of 192.168.0.0 (including 192.168.0.0 255.255.255.0):

access-list 101 permit ip 192.168.0.0 0.0.0.0 255.255.0.0 0.0.0.0 
access-list 101 deny ip 192.168.0.0 0.0.255.255 255.255.0.0 0.0.255.255 

Examples

The following extended access list example will permit route 10.108.0/24 but deny 10.108/16 and all other subnets of 10.108.0.0:

access-list 101 permit ip 10.108.0.0 0.0.0.0 255.255.255.0 0.0.0.0
access-list 101 deny ip 10.108.0.0 0.0.255.255 255.255.0.0 0.0.255.255 

Examples

The following extended access list example will deny all prefixes that are longer than 24 bits and permit all of the shorter prefixes:

access-list 101 deny ip 0.0.0.0 255.255.255.255 255.255.255.0 0.0.0.255 
access-list 101 permit ip 0.0.0.0 255.255.255.255 0.0.0.0 255.255.255.255 

Related Commands

Command

Description

access-list (IP extended)

Defines an extended IP access list.

access-list (IP standard)

Defines a standard IP access list.

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPNv4 address prefixes.

ip as-path access-list

Defines a BGP-related access list.

neighbor filter-list

Sets up a BGP filter.

neighbor peer-group (creating)

Creates a BGP peer group.

route-map (IP)

Defines the conditions for redistributing routes from one routing protocol into another.

neighbor dmzlink-bw

To configure Border Gateway Protocol (BGP) to advertise the bandwidth of links that are used to exit an autonomous system, use the neighbor dmzlink-bw command in address family configuration mode. To disable the linkbandwidthadvertisement, use the no form of this command.

neighbor ip-address dmzlink-bw

no neighbor ip-address dmzlink-bw

Syntax Description

ip-address

IP address of the neighbor router for which the bandwidth of the outbound link is advertised.

Command Default

This command is disabled by default.

Command Modes


Address family configuration (config-router-af)

Command History

Release

Modification

12.2(2)T

This command was introduced.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.0(24)S

This command was integrated into Cisco IOS Release 12.0(24)S.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

The neighbor dmzlink-bw command is used to configure BGP to advertise the bandwidth of the specified external interface as an extended community. This command is configured for links between directly connected external BGP (eBGP) neighbors. The link bandwidth extended community attribute is propagated to iBGP peers when extended community exchange is enabled with the neighbor send-community command. This feature is used with BGP multipath features to configure load balancing over links with unequal bandwidth. This feature is not enabled until the bgp dmzlink-bw command is entered under the address family session for each router that has a directly connected external link.

Examples

In the following example, the BGP Link Bandwidth feature is configured to allow multipath load balancing to distribute link traffic proportionally to the bandwidth of each external link, and to advertise the bandwidth of these links to iBGP peers as an extended community:

Router(config)# router bgp 100
 
Router(config-router)# neighbor 10.10.10.1 remote-as 100
 
Router(config-router)# neighbor 10.10.10.1 update-source Loopback 0
 
Router(config-router)# neighbor 10.10.10.3 remote-as 100
 
Router(config-router)# neighbor 10.10.10.3 update-source Loopback 0 
Router(config-router)# neighbor 172.16.1.1 remote-as 200
 
Router(config-router)# neighbor 172.16.1.1 ebgp-multihop 1 
Router(config-router)# neighbor 172.16.2.2 remote-as 200
 
Router(config-router)# neighbor 172.16.2.2 ebgp-multihop 1 
Router(config-router)# address-family ipv4
 
Router(config-router-af)# bgp dmzlink-bw
 
Router(config-router-af)# neighbor 10.10.10.1 activate
 
Router(config-router-af)# neighbor 10.10.10.1 next-hop-self
 
Router(config-router-af)# neighbor 10.10.10.1 send-community both
 
Router(config-router-af)# neighbor 10.10.10.3 activate
 
Router(config-router-af)# neighbor 10.10.10.3 next-hop-self
 
Router(config-router-af)# neighbor 10.10.10.3 send-community both
 
Router(config-router-af)# neighbor 172.16.1.1
 activate 
Router(config-router-af)# neighbor 172.16.1.1 dmzlink-bw
 
Router(config-router-af)# neighbor 172.16.2.2 activate 
Router(config-router-af)# neighbor 172.16.2.2 dmzlink-bw
Router(config-router-af)# maximum-paths ibgp 6
Router(config-router-af)# maximum-paths 6

Related Commands

Command

Description

bgp dmzlink-bw

Configures BGP to distribute traffic proportionally over external links with unequal bandwidth when multipath load balancing is enabled.

neighbor send-community

Specifies that a communities attribute should be sent to a BGP neighbor.

neighbor ebgp-multihop

To accept and attempt BGP connections to external peers residing on networks that are not directly connected, use the neighbor ebgp-multihop command in router configuration mode. To return to the default, use the no form of this command.

neighbor { ip-address | ipv6-address | peer-group-name } ebgp-multihop [ttl]

no neighbor { ip-address | ipv6-address | peer-group-name } ebgp-multihop

Syntax Description

ip-address

IP address of the BGP-speaking neighbor.

ipv6-address

IPv6 address of the BGP-speaking neighbor.

peer-group-name

Name of a BGP peer group.

ttl

(Optional) Time-to-live in the range from 1 to 255 hops.

Command Default

Only directly connected neighbors are allowed.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

11.0

The peer-group-name argument was added.

12.2(33)SRA

The ipv6-address argument and support for the IPv6 address family were added.

12.2(33)SB

This command was integrated into Cisco IOS Release 12.2(33)SB.

12.2(33)SXI

This command was integrated into Cisco IOS Release 12.2(33)SXI.

Cisco IOS XE Release 3.1S

This command was integrated into Cisco IOS XE Release 3.1S.

Usage Guidelines

This feature should be used only under the guidance of Cisco technical support staff.

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

To prevent the creation of loops through oscillating routes, the multihop will not be established if the only route to the multihop peer is the default route (0.0.0.0).

Examples

The following example allows connections to or from neighbor 10.108.1.1, which resides on a network that is not directly connected:

router bgp 109
 neighbor 10.108.1.1 ebgp-multihop

Related Commands

Command

Description

neighbor advertise-map non-exist-map

Allows a BGP speaker (the local router) to send the default route 0.0.0.0 to a neighbor for use as a default route.

neighbor peer-group (creating)

Creates a BGP peer group.

network (BGP and multiprotocol BGP)

Specifies the list of networks for the BGP routing process.

neighbor fall-over

To enable Border Gateway Protocol (BGP) to monitor the peering session of a specified neighbor for adjacency changes and to deactivate the peering session, use the neighbor fall-over command in address family configuration mode or router configuration mode. To disable BGP monitoring of the neighbor peering session, use the no form of this command.

neighbor { ip-address | ipv6-address } fall-over [ bfd [check-control-plane-failure] | route-map map-name ]

no neighbor { ip-address | ipv6-address } fall-over [ bfd [check-control-plane-failure] | route-map map-name ]

Syntax Description

ip-address

IPv4 address of a BGP neighbor.

ipv6-address

IPv6 address of a BGP neighbor.

bfd

(Optional) Enables Bidirectional Forwarding Detection (BFD) protocol support for fallover.

check-control-plane-failure

(Optional) Retrieves control plane dependent failure (c-bit) information from BFD for BGP graceful restart (GR)/Nonstop Forwarding (NSF) operation.

route-map map-name

(Optional) Specifies the use of a route map by name.

Note   

The route map applies only to a neighbor with an IPv4 address.

Command Default

BGP does not monitor neighbor peering sessions.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.0(29)S

This command was introduced.

12.3(14)T

This command was integrated into Cisco IOS Release 12.3(14)T.

12.4(4)T

This command was modified. The route-map keyword and map-name argument were added to support the BGP Selective Address Tracking feature.

12.2(33)SRA

This command was modified. The bfd keyword was added to support the BFD feature, and this command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SRB

This command was modified. The route-map keyword and map-name argument were added to support the BGP Selective Address Tracking feature.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

12.2(33)SB

This command was modified. The bfd keyword was added to support the BFD feature.

15.1(2)S

This command was modified. The ipv6-address argument was added.

Cisco IOS XE 3.3S

This command was modified. The ipv6-address argument was added.

15.2(3)T

This command was integrated into Cisco IOS Release 15.2(3)T.

Cisco IOS XE Release 3.6S

This command was modified. The check-control-plane-failure keyword was added.

15.2(4)S

This command was integrated into Cisco IOS Release 15.2(4)S.

Cisco IOS XE Release 3.7S

This command was implemented on the Cisco ASR 903 router.

15.1(2)SNG

This command was implemented on the Cisco ASR 901 Series Aggregation Services Routers.

15.2(1)E

This command was integrated into Cisco IOS Release 15.2(1)E.

Usage Guidelines

The neighbor fall-over command is a BGP neighbor session command that is used to enable BGP fast peering session deactivation. BGP fast peering session deactivation improves BGP convergence and response time to adjacency changes with BGP neighbors. BGP fast peering session deactivation is event-driven and is configured on a per-neighbor basis. When BGP fast peering session deactivation is enabled, BGP will monitor the peering session with the specified neighbor. Adjacency changes are detected, and terminated peering sessions are deactivated in between the default or configured BGP scanning interval.

In Cisco IOS Release 12.4(4)T, 12.2(33)SRB, and later releases, the optional route-map keyword and map-name argument are used with this command to determine if a peering session with a BGP neighbor should be deactivated (reset) when a route to the BGP peer changes. The route map is evaluated against the new route, and if a deny statement is returned, the peer session is reset. The route map is not used for session establishment.


Note


Only the match ip address and match source-protocol commands are supported in the route map. No set commands or other match commands are supported.


In Cisco IOS Release 12.2(33)SRA, 12.2(33)SB, and later releases, the optional bfd keyword is used to enable BFD protocol support for fallover. BFD provides fast forwarding path failure detection and a consistent failure detection method for network administrators. Because the network administrator can use BFD to detect forwarding path failures at a uniform rate, rather than the variable rates for different routing protocol hello mechanisms, network profiling and planning is easier, and reconvergence time is consistent and predictable. The main benefit of implementing BFD for BGP is a marked decrease in reconvergence time.

In Cisco IOS Release 15.1(2)S, Cisco IOS XE Release 3.3S, and later releases, an IPv6 address can be specified with the bfd keyword. Once it has been verified that BFD neighbors are up, the output from the show bgp ipv6 unicast neighbors command with a specified IPv6 address will display that BFD is being used to detect fast fallover.

Examples

In the following example, the BGP routing process is configured to monitor and use fast peering session deactivation for the neighbor session with the neighbor at 192.168.1.2:

router bgp 45000 
 neighbor 192.168.1.2 remote-as 40000 
 neighbor 192.168.1.2 fall-over 
 end

In the following example, the BGP peering session is reset if a route with a prefix of /28 or a more specific route to a peer destination is no longer available:

router bgp 45000 
 neighbor 192.168.1.2 remote-as 40000 
 neighbor 192.168.1.2 fall-over route-map CHECK-NBR
 exit
ip prefix-list FILTER28 seq 5 permit 0.0.0.0/0 ge 28
route-map CHECK-NBR permit 10
 match ip address prefix-list FILTER28
 end

In the following example, BFD is enabled for Fast Ethernet interface 0/1/1 with a specified BFD interval. The BGP peering session is also BFD enabled, which will result in a decreased reconvergence time for BGP if any of the forwarding paths to specified neighbors fail.

interface FastEthernet 0/1/1
 ip address 172.16.10.1 255.255.255.0
 bfd interval 50 min_rx 50 multiplier 3
 exit
router bgp 40000
 bgp log-neighbor-changes
 neighbor 172.16.10.2 remote-as 45000 
 neighbor 172.16.10.2 fall-over bfd
 exit

In the following IPv6 example, BFD is enabled for Fast Ethernet interface 0/1/1 with a specified BFD interval. The BGP peering session is also BFD enabled and this will result in a decreased reconvergence time for BGP if any of the forwarding paths to the specified neighbor at 2001:DB8:2:1::4 fail.

ipv6 unicast-routing
ipv6 cef
interface fastethernet 0/1/1
 ipv6 address 2001:DB8:1:1::1/64
 bfd interval 500 min_rx 500 multiplier 3
 no shutdown
 exit
router bgp 65000
 no bgp default ipv4-unicast
 address-family ipv6 unicast
 bgp log-neighbor-changes
 neighbor 2001:DB8:2:1::4 remote-as 45000 
 neighbor 2001:DB8:2:1::4 fall-over bfd
 end

Related Commands

Command

Description

bfd

Sets the baseline BFD session parameters on an interface.

match ip address

Matches IP addresses defined by a prefix list.

match source-protocol

Matches the route type based on the source protocol.

show bgp ipv6 unicast neighbors

Displays information about BGP IPv6 neighbors.

neighbor filter-list

To set up a BGP filter, use the neighbor filter-list command in address family or router configuration mode. To disable this function, use the no form of this command.

neighbor { ip-address | peer-group-name } filter-list access-list-number { in | out }

no neighbor { ip-address | peer-group-name } filter-list access-list-number { in | out }

Syntax Description

ip-address

IP address of the neighbor.

peer-group-name

Name of a BGP peer group.

access-list-number

Number of an autonomous system path access list. You define this access list with the ip as-path access-list command.

in

Access list is applied to incoming routes.

out

Access list is applied to outgoing routes.

Command Default

No BGP filter is used.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

12.0(7)T

Address family configuration mode was added.

12.1

The weight keyword was removed.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

This command establishes filters on both inbound and outbound BGP routes.

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command. Specifying the command with an IP address will override the value inherited from the peer group.


Note


Do not apply both a neighbor distribute-list and a neighbor prefix-list command to a neighbor in any given direction (inbound or outbound). These two commands are mutually exclusive, and only one command ( neighbor distribute-list or neighbor prefix-list) can be applied to each inbound or outbound direction.


Examples

In the following router configuration mode example, the BGP neighbor with IP address 172.16.1.1 is not sent advertisements about any path through or from the adjacent autonomous system 123:

ip as-path access-list 1 deny _123_
ip as-path access-list 1 deny ^123$
 router bgp 109
 network 10.108.0.0
 neighbor 192.168.6.6 remote-as 123
 neighbor 172.16.1.1 remote-as 47
 neighbor 172.16.1.1 filter-list 1 out

In the following address family configuration mode example, the BGP neighbor with IP address 172.16.1.1 is not sent advertisements about any path through or from the adjacent autonomous system 123:

ip as-path access-list 1 deny _123_
ip as-path access-list 1 deny ^123$
router bgp 109
 address-family ipv4 unicast
  network 10.108.0.0
  neighbor 192.168.6.6 remote-as 123
  neighbor 172.16.1.1 remote-as 47
  neighbor 172.16.1.1 filter-list 1 out

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPNv4 address prefixes.

ip as-path access-list

Defines a BGP-related access list.

match as-path

Matches BGP autonomous system path access lists.

neighbor distribute-list

Distributes BGP neighbor information as specified in an access list.

neighbor peer-group (creating)

Creates a BGP peer group.

neighbor prefix-list

Prevents distribution of BGP neighbor information as specified in a prefix list, a CLNS filter expression, or a CLNS filter set.

neighbor weight

Assigns a weight to a neighbor connection.

set weight

Specifies the BGP weight for the routing table.

neighbor ha-mode graceful-restart

To enable or disable the Border Gateway Protocol (BGP) graceful restart capability for a BGP neighbor or peer group, use the neighbor ha-mode graceful-restart command in router configuration mode. To remove from the configuration the BGP graceful restart capability for a neighbor, use the no form of this command.

neighbor { ip-address | peer-group-name } ha-mode graceful-restart [disable]

no neighbor { ip-address | peer-group-name } ha-mode graceful-restart [disable]

Syntax Description

ip-address

IP address of the neighbor.

peer-group-name

Name of a BGP peer group.

disable

(Optional) Disables BGP graceful restart capability for a neighbor.

Command Default

BGP graceful restart capability is disabled.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

12.2(33)SRC

This command was introduced.

12.2(33)SB

This command was integrated into Cisco IOS Release 12.2(33)SB.

15.1(1)SG

This command was integrated into Cisco IOS Release 15.1(1)SG.

Cisco IOS XE 3.3SG

This command was integrated into Cisco IOS XE Release 3.3SG.

Usage Guidelines

The neighbor ha-mode graceful-restart command is used to enable or disable the graceful restart capability for an individual BGP neighbor or peer group in a BGP network. Use the disable keyword to disable the graceful restart capability when graceful restart has been previously enabled for the BGP peer.

The graceful restart capability is negotiated between nonstop forwarding (NSF)-capable and NSF-aware peers in OPEN messages during session establishment. If the graceful restart capability is enabled after a BGP session has been established, the session will need to be restarted with a soft or hard reset.

The graceful restart capability is supported by NSF-capable and NSF-aware routers. A router that is NSF-capable can perform a stateful switchover (SSO) operation (graceful restart) and can assist restarting peers by holding routing table information during the SSO operation. A router that is NSF-aware functions like a router that is NSF-capable but cannot perform an SSO operation.

To enable the BGP graceful restart capability globally for all BGP neighbors, use the bgp graceful-restartcommand. When the BGP graceful restart capability is configured for an individual neighbor, each method of configuring graceful restart has the same priority, and the last configuration instance is applied to the neighbor.

Use the show ip bgp neighbors command to verify the BGP graceful restart configuration for BGP neighbors.

Examples

The following example enables the BGP graceful restart capability for the BGP neighbor, 172.21.1.2:

router bgp 45000
 bgp log-neighbor-changes
 address-family ipv4 unicast
 neighbor 172.21.1.2 remote-as 45000
 neighbor 172.21.1.2 activate
 neighbor 172.21.1.2 ha-mode graceful-restart
 end

The following example enables the BGP graceful restart capability globally for all BGP neighbors and then disables the BGP graceful restart capability for the BGP peer group PG1. The BGP neighbor 172.16.1.2 is configured as a member of the peer group PG1 and inherits the disabling of the BGP graceful restart capability.

router bgp 45000
 bgp log-neighbor-changes
 bgp graceful-restart
 address-family ipv4 unicast
 neighbor PG1 peer-group
 neighbor PG1 remote-as 45000
 neighbor PG1 ha-mode graceful-restart disable
 neighbor 172.16.1.2 peer-group PG1
 end

Related Commands

Command

Description

bgp graceful-restart

Enables the BGP graceful restart capability globally for all BGP neighbors.

ha-mode graceful-restart

Enables or disables the BGP graceful restart capability for a BGP peer session template.

show ip bgp neighbors

Displays information about the TCP and BGP connections to neighbors.

neighbor ha-mode sso

To configure a Border Gateway Protocol (BGP) neighbor to support BGP nonstop routing (NSR) with stateful switchover (SSO), use the neighbor ha-mode sso command in the appropriate command mode. To remove the configuration, use the no form of this command.

neighbor { ip-address | ipv6-address } ha-mode sso

no neighbor { ip-address | ipv6-address } ha-mode sso

Syntax Description

ip-address

IP address of the neighboring router.

ipv6-address

IPv6 address of the neighboring router.

Command Default

BGP NSR with SSO support is disabled.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Session-template configuration

Command History

Release

Modification

12.2(28)SB

This command was introduced.

15.0(1)S

This command was integrated into Cisco IOS Release 15.0(1)S.

Cisco IOS XE 3.1S

This command was integrated into Cisco IOS XE Release 3.1S.

Cisco IOS XE 3.6S

This command was modified. It is supported in router configuration mode.

15.2(2)S

This command was modified. It is supported in router configuration mode.

Cisco IOS XE 3.7S

This command was implemented on the Cisco ASR 903 router.

Usage Guidelines

The neighbor ha-mode sso command is used to configure a BGP neighbor to support BGP NSR with SSO. BGP NSR with SSO is disabled by default.

BGP NSR with SSO is supported in BGP peer, BGP peer group, and BGP session template configurations. To configure BGP NSR with SSO in BGP peer and BGP peer group configurations, use the neighbor ha-mode sso command in address family configuration mode for address family BGP peer sessions. To include support for Cisco BGP NSR with SSO in a peer session template, use the ha-mode sso command in session-template configuration mode.

Examples

The following example shows how to configure a BGP neighbor to support SSO:

Router(config-router-af)# neighbor 10.3.32.154 ha-mode sso

Related Commands

Command

Description

show ip bgp sso summary

Displays the state of NSR established sessions for the IPv4 address family or all address families.

show ip bgp vpnv4

Displays VPN address information from the BGP table.

show ip bgp vpnv4 all sso summary

Displays the number of BGP neighbors that support SSO.

neighbor inherit peer-policy

To send a peer policy template to a neighbor so that the neighbor can inherit the configuration, use the neighbor inherit peer-policycommand in address family or router configuration mode. To stop sending the peer policy template, use the no form of this command.

neighbor ip-address inherit peer-policy policy-template-name

no neighbor ip-address inherit peer-policy policy-template-name

Syntax Description

ip-address

IP address of the neighbor.

policy-template-name

Name or tag for the peer policy template.

Command Default

No default behavior or values

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.0(24)S

This command was introduced.

12.2(18)S

This command was integrated into Cisco IOS Release 12.2(18)S.

12.3(4)T

This command was integrated into Cisco IOS Release 12.3(4)T.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

This command is used to send locally configured policy templates to the specified neighbor. If the policy template is configured to inherit configurations from other peer policy templates, the specified neighbor will also indirectly inherit these configurations from the other peer policy templates. A directly applied peer policy template can directly or indirectly inherit configurations from up to seven peer policy templates. So, a total of eight peer policy templates can be applied to a neighbor or neighbor group.


Note


A Border Gateway Protocol (BGP) neighbor cannot be configured to work with both peer groups and peer templates. A BGP neighbor can be configured to belong only to a peer group or to inherit policies only from peer templates.


Examples

The following example configures the 10.0.0.1 neighbor in address family configuration mode to inherit the peer policy template name CUSTOMER-A. The 10.0.0.1 neighbor will also indirectly inherit the peer policy templates in CUSTOMER-A. The explicit remote-as statement is required for the neighbor inherit statement to work. If a peering is not configured, the specified neighbor will not accept the session template.

Router(config)# router bgp 101
Router(config-router)# neighbor 10.0.0.1 remote-as 202
Router(config-router)# address-family ipv4 unicast
Router(config-router-af)# neighbor 10.0.0.1 inherit peer-policy CUSTOMER-A
Router(config-router-af)# exit

Related Commands

Command

Description

exit peer-policy

Exits policy-template configuration mode and enters router configuration mode.

inherit peer-policy

Configures a peer policy template to inherit the configuration from another peer policy template.

show ip bgp neighbors

Displays information about the TCP and BGP connections to neighbors.

show ip bgp template peer-policy

Displays locally configured peer policy templates.

template peer-policy

Creates a peer policy template and enters policy-template configuration mode.

neighbor inherit peer-session

To send a peer session template to a neighbor so that the neighbor can inherit the configuration, use the neighbor inherit peer-sessioncommand in address family or router configuration mode. To stop sending the peer session template, use the no form of this command.

neighbor ip-address inherit peer-session session-template-name

no neighbor ip-address inherit peer-session session-template-name

Syntax Description

ip-address

IP address of the neighbor.

session-template-name

Name or tag for the peer session template.

Command Default

No default behavior or values

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.0(24)S

This command was introduced.

12.2(18)S

This command was integrated into Cisco IOS Release 12.2(18)S.

12.3(4)T

This command was integrated into Cisco IOS Release 12.3(4)T.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

This command is used to send locally configured session templates to the specified neighbor. If the session template is configured to inherit configurations from other session templates, the specified neighbor will also indirectly inherit these configurations from the other session templates. A neighbor can directly inherit only one peer session template and indirectly inherit up to seven peer session templates.


Note


A Border Gateway Protocol (BGP) neighbor cannot be configured to work with both peer groups and peer templates. A BGP neighbor can be configured to belong only to a peer group or to inherit policies only from peer templates.


Examples

The following example configures the 172.16.0.1 neighbor to inherit the CORE1 peer session template. The 172.16.0.1 neighbor will also indirectly inherit the configuration from the peer session template named INTERNAL-BGP. The explicit remote-as statement is required for the neighbor inherit statement to work. If a peering is not configured, the specified neighbor will not accept the session template.

Router(config)# router bgp 101
Router(config)# neighbor 172.16.0.1 remote-as 202
Router(config-router)# neighbor 172.16.0.1 inherit peer-session CORE1

Related Commands

Command

Description

exit peer-session

Exits session-template configuration mode and enters router configuration mode.

inherit peer-session

Configures a peer session template to inherit the configuration from another peer session template.

show ip bgp neighbors

Displays information about the TCP and BGP connections to neighbors.

show ip bgp template peer-session

Displays locally configured peer session templates.

template peer-session

Creates a peer session template and enters session-template configuration mode.

neighbor internal-vpn-client

To enable provider edge (PE) or customer edge (CE) devices to exchange Border Gateway Protocol (BGP) routing by peering as internal BGP(iBGP), use the neighbor internal-vpn-client command in address family configuration mode. To disable this command, use the no form of this command.

neighbor { ip-address | peer-group-name | ipv6-address } internal-vpn-client

no neighbor { ip-address | peer-group-name | ipv6-address } internal-vpn-client

Syntax Description

ip-address

IP address of the neighboring device.

peer-group-name

Name of the BGP peer group.

ipv6-address

IPv6 address of the iBGP neighbor.

Command Default

No default behavior or values

Command Modes

Address family configuration (config-router-af)

Command History

Release Modification

Cisco IOS XE Release 3.10S

This command was introduced.

15.4(1)T

This command was integrated into Cisco IOS Release 15.4(1)T.

Usage Guidelines

The neighbor ip-address internal-vpn-client command enables PE devices to make the entire VPN cloud act like an internal VPN client to the CE devices connected internally. This command is used so that existing internal BGP VRF lite scenarios are not affected.

You need not configure autonomous system override for CE devices after enabling this command..

Examples

The following example shows how to enable neighbor ip-address internal-vpn-client command.

Device(config-router)# address-family ipv4 vrf blue
Device(config-router-af)# neighbor 10.0.0.1 internal-vpn-client

Related Commands

Command

Description

neighbor activate

Enables the exchange of information with a BGP neighbor.

neighbor local-as

To customize the AS_PATH attribute for routes received from an external Border Gateway Protocol (eBGP) neighbor, or to configure the BGP—Support for iBGP Local-AS feature, use the neighbor local-as command in address family or router configuration mode. To disable AS_PATH attribute customization or iBGP Local-AS support, use the no form of this command.

neighbor { ip-address | ipv6-address | peer-group-name } local-as [ autonomous-system-number [ no-prepend [ replace-as [dual-as] ] ] ]

no neighbor { ip-address | ipv6-address | peer-group-name } local-as

Syntax Description

ip-address

IPv4 address of the eBGP neighbor.

ipv6-address

IPv6 address of the eBGP neighbor.

peer-group

Name of a BGP peer group.

autonomous-system-number

(Optional) Number of an autonomous system to prepend to the AS_PATH attribute. The range of values for this argument is any valid autonomous system number from 1 to 65535.

  • In Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, and later releases, 4-byte autonomous system numbers are supported in the range from 65536 to 4294967295 in asplain notation and in the range from 1.0 to 65535.65535 in asdot notation.

  • In Cisco IOS Release 12.0(32)S12, 12.4(24)T, and Cisco IOS XE Release 2.3, 4-byte autonomous system numbers are supported in the range from 1.0 to 65535.65535 in asdot notation only.

For more details about autonomous system number formats, see the router bgp command.

Note   

With this argument, you cannot specify the autonomous system number from the local BGP routing process or from the network of the remote peer.

no-prepend

(Optional) Does not prepend the local autonomous system number to any routes received from the eBGP neighbor.

replace-as

(Optional) Replaces the real autonomous system number with the local autonomous system number in the eBGP updates. The autonomous system number from the local BGP routing process is not prepended.

dual-as

(Optional) Configures the eBGP neighbor to establish a peering session by using the real autonomous system number (from the local BGP routing process) or by using the autonomous system number configured with the autonomous-system-number argument (local-as).

Command Default

The autonomous system number from the local BGP routing process is prepended to all external routes by default.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.0(5)S

This command was introduced.

12.0(5)T

CLI support for address family configuration mode was added.

12.2(8)T

The no-prepend keyword was added.

12.2(14)S

The no-prepend keyword was integrated into Cisco IOS Release 12.2(14)S.

12.0(18)S

The no-prepend keyword was integrated into Cisco IOS Release 12.0(18)S.

12.0(27)S

The replace-as and dual-as keywords were added.

12.2(25)S

The replace-as and dual-as keywords were integrated into Cisco IOS Release 12.2(25)S.

12.3(11)T

The replace-as and dual-as keywords were integrated into Cisco IOS Release 12.3(11)T.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.

12.0(32)S12

This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.

12.0(32)SY8

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

12.4(24)T

This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.

Cisco IOS XE Release 2.3

This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.

12.2(33)SXI1

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

12.0(33)S3

This command was modified. Support for asplain notation was added and the default format for 4-byte autonomous system numbers is now asplain.

Cisco IOS XE Release 2.4

This command was modified. Support for asplain notation was added and the default format for 4-byte autonomous system numbers is now asplain.

12.2(33)SRE

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

12.2(33)XNE

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

15.1(1)SG

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

Cisco IOS XE Release 3.3SG

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

15.3(2)S

This command was modified. It can be used to configure the iBGP Local-AS feature.

Cisco IOS XE Release 3.9S

This command was modified. It can be used to configure the iBGP Local-AS feature.

15.2(1)E

This command was integrated into Cisco IOS Release 15.2(1)E.

Usage Guidelines

The neighbor local-as command is used to customize the AS_PATH attribute by adding and removing autonomous system numbers for routes received from eBGP neighbors. The configuration of this command allows a router to appear to external peers as a member of another autonomous system for the purpose of autonomous system number migration. This feature simplifies the process of changing the autonomous system number in a BGP network by allowing the network operator to migrate customers to new configurations during normal service windows without disrupting existing peering arrangements.


Caution


BGP prepends the autonomous system number from each BGP network that a route traverses to maintain network reachability information and to prevent routing loops. This command should be configured only for autonomous system migration, and should be deconfigured after the transition has been completed. This procedure should be attempted only by an experienced network operator. Routing loops can be created through improper configuration.


This command can be used for only true eBGP peering sessions. This command does not work for two peers in different subautonomous systems of a confederation.

This command supports individual peering sessions and configurations applied through peer groups and peer templates. If this command is applied to a group of peers, the individual peers cannot be customized.

In Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, and later releases, the Cisco implementation of 4-byte autonomous system numbers uses asplain—65538 for example—as the default regular expression match and output display format for autonomous system numbers, but you can configure 4-byte autonomous system numbers in both the asplain format and the asdot format as described in RFC 5396. To change the default regular expression match and output display of 4-byte autonomous system numbers to asdot format, use the bgp asnotation dot command followed by the clear ip bgp * command to perform a hard reset of all current BGP sessions.

In Cisco IOS Release 12.0(32)S12, 12.4(24)T, and Cisco IOS XE Release 2.3, the Cisco implementation of 4-byte autonomous system numbers uses asdot—1.2 for example—as the only configuration format, regular expression match, and output display, with no asplain support.

To ensure a smooth transition, we recommend that all BGP speakers within an AS that is identified using a 4-byte AS number be upgraded to support 4-byte AS numbers.

BGP—Support for iBGP Local-AS

There can be scenarios where the network administrator wants iBGP attributes to be passed unmodified, typically to facilitate the merging of two autonomous systems. The BGP—Support for iBGP Local-AS feature causes BGP to treat an iBGP local-AS connection as an iBGP connection and pass the LOCAL_PREF, ORIGINATOR_ID, CLUSTER_ID, and CLUSTER_LIST attributes unmodified. If a BGP peer has a neighbor remote-as command and a neighbor local-as command that specify the same AS number, the session with that neighbor is treated as iBGP when advertising routes received in this session to iBGP peers that have no neighbor local-as command configured. That means that during re-advertisement, BGP will pass the LOCAL_PREF, ORIGINATOR_ID, CLUSTER_ID, and CLUSTER_LIST attributes unmodified instead of dropping them.


Note


The other keywords in the neighbor local-as command (no-prepend, replace-as, and dual-as) do not affect an iBGP local-AS client. Even if these keywords are configured for an iBGP client, no action is taken to modify the AS_PATH.

Examples

The following example establishes peering between Router 1 and Router 2 through autonomous system 300, using the local-as feature:

router bgp 100
 address-family ipv4 unicast 
  neighbor 172.16.1.1 remote-as 200
  neighbor 172.16.1.1 local-as 300

router bgp 200
 address-family ipv4 unicast 
  neighbor 10.0.0.1 remote-as 300

The following example configures BGP to not prepend autonomous system 500 to routes received from the 192.168.1.1 neighbor:

router bgp 400
 address-family ipv4 multicast
  network 192.168.0.0
  neighbor 192.168.1.1 local-as 500 no-prepend 

The following example strips private autonomous system 64512 from outbound routing updates for the 172.20.1.1 neighbor and replaces it with autonomous system 600:

router bgp 64512 
 address-family ipv4 unicast 
  neighbor 172.20.1.1 local-as 600 no-prepend replace-as 
  neighbor 172.20.1.1 remove-private-as 

The following examples show the configurations for two provider networks and one customer network. Router 1 belongs to AS 100, and Router 2 belongs to AS 200. AS 200 is being merged into AS 100. This transition must occur without interrupting service to Router 3 in AS 300 (customer network). The neighbor local-as command is configured on Router 1 to allow Router 3 to maintain peering with AS 200 during this transition. After the transition is complete, the configuration on Router 3 can be updated to peer with AS 100 during a normal maintenance window or during other scheduled downtime.

interface Serial3/0
 ip address 10.3.3.11 255.255.255.0
!
router bgp 100
 no synchronization
 bgp router-id 100.0.0.11
 neighbor 10.3.3.33 remote-as 300
 neighbor 10.3.3.33 local-as 200 no-prepend replace-as dual-as

interface Serial3/0
 ip address 10.3.3.11 255.255.255.0
 !
router bgp 200 
 bgp router-id 100.0.0.11
 neighbor 10.3.3.33 remote-as 300

interface Serial3/0
 ip address 10.3.3.33 255.255.255.0
 !
router bgp 300
 bgp router-id 100.0.0.3
 neighbor 10.3.3.11 remote-as 200 

To complete the migration after the two autonomous systems have merged, the peering session is updated on Router 3:

neighbor 10.3.3.11 remote-as 100

The following example configures BGP to not prepend the 4-byte AS number of 65536 in asplain format to routes received from the 192.168.1.2 neighbor. This example requires Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, or a later release.

router bgp 65538
 address-family ipv4 multicast
  network 192.168.0.0
  neighbor 192.168.1.2 local-as 65536 no-prepend

The following example configures BGP to not prepend the 4-byte AS number of 1.0 in asdot format to routes received from the 192.168.1.2 neighbor. This example requires Cisco IOS Release 12.0(32)SY8, 12.0(32)S12, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, 12.4(24)T, or Cisco IOS XE Release 2.3.

router bgp 1.2
 address-family ipv4 multicast
  network 192.168.0.0
  neighbor 192.168.1.2 local-as 1.0 no-prepend

The following example configures a route reflector (RR) in AS 4000 to treat BGP sessions with the neighbor in AS 2500 as iBGP sessions. That is, iBGP attributes (LOCAL_PREF, ORIGINATOR_ID, CLUSTER_ID, and CLUSTER_LIST) will not be dropped from routes in advertisements to and from the neighbor; the attributes will be preserved. AS 2500 will be prepended to the AS_PATH attribute in all routes to and from the neighbor. Additionally, the RR is enabled so that it can be configured with iBGP policies (by using a route map, which is not shown here).

router bgp 4000 
 neighbor 192.168.1.1 remote-as 2500
 neighbor 192.168.1.1 local-as 2500
 neighbor 192.168.1.1 route-reflector-client
 address-family vpnv4
  neighbor 192.168.1.1 allow-policy
! 
 address-family vpnv6
  neighbor 192.168.1.1 allow-policy

Related Commands

Command

Description

bgp asnotation dot

Changes the default display and the regular expression match format of BGP 4-byte autonomous system numbers from asplain (decimal values) to dot notation.

neighbor allow-policy

Allows iBGP policies to be preserved and passed on to a peer in a different AS.

neighbor remote-as

Adds an entry to the BGP or multiprotocol BGP neighbor table.

neighbor remove-private-as

Removes private autonomous system numbers from outbound routing updates.

router bgp

Configures the BGP routing process.

show ip bgp

Displays entries in the BGP routing table.

show ip bgp neighbors

Displays information about BGP neighbors.

neighbor maximum-prefix (BGP)

To control how many prefixes can be received from a neighbor, use the neighbor maximum-prefix command in router configuration mode. To disable this function, use the no form of this command.

neighbor { ip-address | peer-group-name } maximum-prefix maximum [threshold] [ restart restart-interval ] [warning-only]

no neighbor { ip-address | peer-group-name } maximum-prefix maximum

Syntax Description

ip-address

IP address of the neighbor.

peer-group-name

Name of a Border Gateway Protocol (BGP) peer group.

maximum

Maximum number of prefixes allowed from the specified neighbor. The number of prefixes that can be configured is limited only by the available system resources on a router.

threshold

(Optional) Integer specifying at what percentage of the maximum-prefix limit the router starts to generate a warning message. The range is from 1 to 100; the default is 75.

restart

(Optional) Configures the router that is running BGP to automatically reestablish a peering session that has been disabled because the maximum-prefix limit has been exceeded. The restart timer is configured with the restart-interval argument.

restart-interval

(Optional) Time interval (in minutes) that a peering session is reestablished. The range is from 1 to 65535 minutes.

warning-only

(optional) Allows the router to generate a sys-log message when the maximum-prefix limitis exceeded, instead of terminating the peering session.

Command Default

This command is disabled by default. Peering sessions are disabled when the maximum number of prefixes is exceeded. If the restart-interval argument is not configured, a disabled session will stay down after the maximum-prefix limit is exceeded.

threshold : 75 percent

Command Modes


Router configuration (config-router)

Command History

Release

Modification

11.3

This command was introduced.

12.0(22)S

The restart keyword was introduced.

12.2(15)T

The restart keyword was integrated into Cisco IOS Release 12.2(15)T.

12.2(18)S

The restart keyword was integrated into Cisco IOS Release 12.2(18)S.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

15.2(4)S

This command was integrated into Cisco IOS Release 15.2(4)S.

Usage Guidelines

The neighbor maximum-prefixcommand allows you to configure a maximum number of prefixes that a Border Gateway Protocol (BGP) routing process will accept from the specified peer. This feature provides a mechanism (in addition to distribute lists, filter lists, and route maps) to control prefixes received from a peer.

When the number of received prefixes exceeds the maximum number configured, BGP disables the peering session (by default). If the restart keyword is configured, BGP will automatically reestablish the peering session at the configured time interval. If the restart keyword is not configured and a peering session is terminated because the maximum prefix limit has been exceed, the peering session will not be be reestablished until the clear ip bgp command is entered. If the warning-only keyword is configured, BGP sends only a log message and continues to peer with the sender.

There is no default limit on the number of prefixes that can be configured with this command. Limitations on the number of prefixes that can be configured are determined by the amount of available system resources.

Examples

In the following example, the maximum prefixes that will be accepted from the 192.168.1.1 neighbor is set to 1000:

Router(config)# router bgp 40000
 
Router(config-router)# network 192.168.0.0
 
Router(config-router)# neighbor 192.168.1.1 maximum-prefix 1000

In the following example, the maximum number of prefixes that will be accepted from the 192.168.2.2 neighbor is set to 5000. The router is also configured to display warning messages when 50 percent of the maximum-prefix limit (2500 prefixes) has been reached.

Router(config)# router bgp 40000 
Router(config-router)# network 192.168.0.0
 
Router(config-router)# neighbor 192.168.2.2 maximum-prefix 5000 50

In the following example, the maximum number of prefixes that will be accepted from the 192.168.3.3 neighbor is set to 2000. The router is also configured to reestablish a disabled peering session after 30 minutes.

Router(config)# router bgp 40000
 
Router(config-router) network 192.168.0.0
 
Router(config-router)# neighbor 192.168.3.3 maximum-prefix 2000 restart 30

In the following example, warning messages will be displayed when the threshold of the maximum-prefix limit (500 x 0.75 = 375) for the 192.168.4.4 neighbor is exceeded:

Router(config)# router bgp 40000
 
Router(config-router)# network 192.168.0.0
 
Router(config-router)# neighbor 192.168.4.4 maximum-prefix 500 warning-only
 

Related Commands

Command

Description

clear ip bgp

Resets a BGP connection using BGP soft reconfiguration.

neighbor next-hop-self

To configure a router as the next hop for a BGP-speaking neighbor or peer group, use the neighbor next-hop-self command in router configuration mode. To disable this feature, use the no form of this command.

neighbor { ip-address | peer-group-name } next-hop-self [ all ]

no neighbor { ip-address | peer-group-name } next-hop-self [ all ]

Syntax Description

ip-address

IP address of the BGP-speaking neighbor.

peer-group-name

Name of a BGP peer group.

all

(Optional) Specifies that the next hop of both eBGP- and iBGP-learned routes is updated by the route reflector (RR).

Command Default

This command is disabled by default.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

11.0

The peer-group-name argument was added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

15.1(1)SY

This command was modified. The optional all keyword was added.

15.2(2)SNG

This command was implemented on the Cisco ASR 901 Series Aggregation Services Routers.

Usage Guidelines

This command is useful in unmeshed networks (such as Frame Relay or X.25) where BGP neighbors may not have direct access to all other neighbors on the same IP subnet.

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command. Specifying the command with an IP address will override the value inherited from the peer group.

For a finer granularity of control, see the set ip next-hop command.

If you do not use the optional all keyword, the next hop of only eBGP-learned routes will be updated by the RR. With the all keyword configured, the next hop of both eBGP- and iBGP-learned routes will be updated by the RR.

Both the no neighbor {ip-address | peer-group-name} next-hop-self and the no neighbor {ip-address | peer-group-name} next-hop-self all commands can be used to disable next-hop-self for both eBGP and iBGP paths (if any or both of them are configured).

Examples

The following example forces all updates destined for 10.108.1.1 to advertise this router as the next hop:

router bgp 109
 neighbor 10.108.1.1 next-hop-self

Related Commands

Command

Description

neighbor peer-group (creating)

Creates a BGP peer group.

set ip next-hop (BGP)

Indicates where to output packets that pass a match clause of a route map for policy routing.

neighbor next-hop-unchanged

To enable an external BGP (eBGP) peer that is configured as multihop to propagate the next hop unchanged, use the neighbor next-hop-unchanged command in address family or router configuration mode. To disable that propagation of the next hop being unchanged, use the no form of this command.

neighbor { ip-address | ipv6-address | peer-group-name } next-hop-unchanged [allpaths]

no neighbor { ip-address | ipv6-address | peer-group-name } next-hop-unchanged [allpaths]

Syntax Description

ip-address

Propagate the iBGP path’s next hop unchanged for this IPv4 neighbor.

ipv6-address

Propagate the iBGP path’s next hop unchanged for this IPv6 neighbor.

peer-group-name

Propagate the iBGP path’s next hop unchanged for this BGP peer group.

allpaths

(Optional) Propagate the next hop unchanged, for all paths (iBGP and eBGP) to this neighbor.

Command Default

This command is disabled by default.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.0(16)ST

This command was introduced.

12.2

This command was integrated into Cisco IOS Release 12.2.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SRB

This command was modified. The allpaths keyword was added.

12.2(33)SB

This command was integrated into Cisco IOS Release 12.2(33)SB.

12.2(33)SXI

This command was integrated into Cisco IOS Release 12.2(33)SXI.

Cisco IOS XE 2.1

This command was integrated into Cisco IOS XE Release 2.1.

Usage Guidelines

By default, for eBGP, the next hop to reach a connected network is the IP address of the neighbor that sent the update. Therefore, as an update goes from router to router, the next hop typically changes to be the address of the neighbor that sent the update (the router’s own address).

However, there might be a scenario where you want the next hop to remain unchanged. The neighbor next-hop-unchanged command is used to propagate the next hop unchanged for multihop eBGP peering sessions. This command is configured on an eBGP neighbor, but the neighbor propagates routes learned from iBGP;that is, the neighbor propagates the next hop of iBGP routes toward eBGP.


Caution


Using the neighbor next-hop-unchanged command or incorrectly altering the BGP next hop can cause inconsistent routing, routing loops, or a loss of connectivity. It should only be attempted by someone who has a good understanding of the design implications.


This command can be used to configure MPLS VPNs between service providers by not modifying the next hop attribute when advertising routes to an eBGP peer.

Examples

The following example configures a multihop eBGP peer at 10.0.0.100 in a remote autonomous system (AS). When the local router sends updates to that peer, it will send them without modifying the next hop attribute.

router bgp 65535
 address-family ipv4
 neighbor 10.0.0.100 remote-as 65600
 neighbor 10.0.0.100 activate 
 neighbor 10.0.0.100 ebgp-multihop 255
 neighbor 10.0.0.100 next-hop-unchanged
 end

Related Commands

Command

Description

address-family ipv4

Enters address family configuration mode for configuring routing sessions, such as BGP, RIP, or static routing sessions, that use standard IPv4 address prefixes.

address-family vpnv4

Enters address family configuration mode for configuring routing sessions, such as BGP, RIP, or static routing sessions, that use standard VPNv4 address prefixes.

neighbor ebgp-multihop

Accepts and attempts BGP connections to external peers residing on networks that are not directly connected.

neighbor next-hop-self

Configures the router as the next hop for a BGP-speaking neighbor or peer group.

neighbor password

To enable message digest5 (MD5) authentication on a TCP connection between two BGP peers, use the neighbor password command in router configuration mode. To disable this function, use the no form of this command.

neighbor { ip-address | peer-group-name } password string

no neighbor { ip-address | peer-group-name } password

Syntax Description

ip-address

IP address of the BGP-speaking neighbor.

peer-group-name

Name of a BGP peer group.

string

Case-sensitive password of up to 25 characters in length. The first character cannot be a number. The string can contain any alphanumeric characters, including spaces. You cannot specify a password in the format number-space-anything. The space after the number can cause authentication to fail.

Command Default

MD5 is not authenticated on a TCP connection between two BGP peers.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

11.0

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

12.4(24)T

This command was integrated into Cisco IOS Release 12.2(24)T. The password was restricted to 25 characters regardless of whether the service password-encryptioncommand was enabled.

Usage Guidelines

You can configure MD5 authentication between two BGP peers, meaning that each segment sent on the TCP connection between the peers is verified. MD5 authentication must be configured with the same password on both BGP peers; otherwise, the connection between them will not be made. Configuring MD5 authentication causes the Cisco IOS software to generate and check the MD5 digest of every segment sent on the TCP connection.

When configuring you can provide a case-sensitive password of up to 25 characters regardless of whether the service password-encryption command is enabled . If the length of password is more than 25 characters, an error message is displayed and the password is not accepted. The string can contain any alphanumeric characters, including spaces. A password cannot be configured in the number-space-anything format. The space after the number can cause authentication to fail. You can also use any combination of the following symbolic characters along with alphanumeric characters:

` ~ ! @ # $ % ^ & * ( ) - _ = + | \ } ] { [ “ ‘ : ; / > < . , ?


Caution


If the authentication string is configured incorrectly, the BGP peering session will not be established. We recommend that you enter the authentication string carefully and verify that the peering session is established after authentication is configured.


If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

If a router has a password configured for a neighbor, but the neighbor router does not, a message such as the following will appear on the console while the routers attempt to establish a BGP session between them:

%TCP-6-BADAUTH: No MD5 digest from [peer’s IP address]:11003 to [local router’s IP address]:179

Similarly, if the two routers have different passwords configured, a message such as the following will appear on the screen:

%TCP-6-BADAUTH: Invalid MD5 digest from [peer’s IP address]:11004 to [local router’s IP address]:179

Configuring an MD5 Password in an Established BGP Session

If you configure or change the password or key used for MD5 authentication between two BGP peers, the local router will not tear down the existing session after you configure the password. The local router will attempt to maintain the peering session using the new password until the BGP hold-down timer expires. The default time period is 180 seconds. If the password is not entered or changed on the remote router before the hold-down timer expires, the session will time out.


Note


Configuring a new timer value for the hold-down timer will only take effect after the session has been reset. So, it is not possible to change the configuration of the hold-down timer to avoid resetting the BGP session.


Examples

The following example configures MD5 authentication for the peering session with the 10.108.1.1 neighbor. The same password must be configured on the remote peer before the hold-down timer expires.

router bgp 109
 neighbor 10.108.1.1 password bla4u00=2nkq

The following example configures a password for more than 25 characters when the service password-encryption command is disabled.

Router(config)# router bgp 200
Router(config-router)# bgp router-id 2.2.2.2
Router(config-router)# neighbor remote-as 3
Router(config-router)# neighbor 209.165.200.225 password 1234567891234567891234567890   
% BGP: Password length must be less than or equal to 25.
Router(config-router)# do show run | i password
no service password-encryption
 neighbor 209.165.200.225 password 1234567891234567891234567

In the following example an error message occurs when you configure a password for more than 25 characters when the service password-encryption command is enabled.

Router(config)# service password-encryption
Router(config)# router bgp 200
Router(config-router)# bgp router-id 2.2.2.2
Router(config-router)# neighbor 209.165.200.225 remote-as 3
Router(config-router)# neighbor 209.165.200.225 password 1234567891234567891234567890   
% BGP: Password length must be less than or equal to 25.
Router(config-router)# do show run | i password
service password-encryption
 neighbor 209.165.200.225 password 1234567891234567891234567

Related Commands

Command

Description

neighbor peer-group (creating)

Creates a BGP peer group.

service password-encryption

Encrypts passwords.

neighbor path-attribute discard

To configure the device to discard specific path attributes from Update messages from the specified neighbor, use the neighbor path-attribute discard command in router configuration mode. To disable this function, use the no form of this command.

neighbor { ip-address | ipv6-address } path-attribute discard { attribute-value | range start-value end-value } in

no neighbor { ip-address | ipv6-address } path-attribute discard { attribute-value | range start-value end-value } in

Syntax Description

ip-address

IP address of the neighbor.

ipv6-address

IPv6 address of the neighbor.

attribute-value

Value of a path attribute to discard, in the range from 1 to 255.

range start

Starting value of a range of path attributes to discard, in the range from 1 to 255.

end

Ending value of a range of path attributes to discard, in the range from 1 to 255.

in

Discard is applied to incoming Update messages.

Command Default

No path attributes are removed from Update messages.

Command Modes

Router configuration (config-router)

Command History

Release

Modification

15.2(4)S

This command was introduced.

Cisco IOS XE Release 3.7S

This command was integrated into Cisco IOS Release XE 3.7S.

15.3(1)T

This command was integrated into Cisco IOS Release 15.3(1)T.

Usage Guidelines

This command provides a security mechanism whereby one or more unwanted path attributes are dropped (discarded) from Update messages. The rest of the Update message is processed normally. Specify either a single attribute value or a range of attribute values to be discarded.

Attribute types 1, 2, 3, 4, 8, 14, 15, and 16 cannot be specified to be discarded. Attribute type 5 (localpref), type 9 (Originator), and type 10 (Cluster-ID) can be specified for discard for eBGP neighbors only.

Configuring this command will trigger an inbound Route Refresh to ensure that the BGP routing table is up to date.

Examples

In the following example, path attributes 100 and 128 are dropped from Update messages from the specified neighbor:

router bgp 65000
 neighbor 2001:DB8:1::1 path-attribute discard 100 in
 neighbor 2001:DB8:1::1 path-attribute discard 128 in
 

In the following example, all path attributes in the range from 17 to 255 are dropped from Update messages from the specified neighbor:


router bgp 65000
 neighbor 2001:DB8:1::1 path-attribute discard range 17 255 in 

Related Commands

Command

Description

neighbor path-attribute treat-as-withdraw

Configures the device to treat as withdrawn any unwanted path attributes from the specified neighbor, so those prefixes are removed from the BGP routing table.

show ip bgp neighbor

Displays the configured discard and treat-as-withdraw attribute values and counters of incoming Update messages containing those attributes.

show ip bgp path-attribute discard

Displays all prefixes for which an attribute has been discarded.

show ip bgp path-attribute unknown

Displays all prefixes that have an unknown attribute.

show ip bgp vpnv4 all

Displays the unknown attributes and discarded attributes associated with a prefix.

neighbor path-attribute treat-as-withdraw

To treat-as-withdraw updates from specified neighbors containing specified path attributes, use the neighbor path-attribute discard command in router configuration mode. To disable this function, use the no form of this command.

neighbor { ip-address | ipv6-address } path-attribute treat-as-withdraw { attribute-value | range start-value end-value } in

no neighbor { ip-address | ipv6-address } path-attribute treat-as-withdraw { attribute-value | range start-value end-value } in

Syntax Description

ip-address

IP address of the neighbor.

ipv6-address

IPv6 address of the neighbor.

attribute-value

Value of a path attribute, in the range from 1 to 255.

range start

Starting value of a range of path attributes, in the range from 1 to 255.

end

Ending value of a range of path attributes, in the range from 1 to 255.

in

Command is applied to incoming Update messages.

Command Default

No prefixes are withdrawn from the BGP routing table based on path attribute.

Command Modes

Router configuration (config-router)

Command History

Release

Modification

15.2(4)S

This command was introduced.

Cisco IOS XE Release 3.7S

This command was integrated into Cisco IOS Release XE 3.7S.

15.3(1)T

This command was integrated into Cisco IOS Release 15.3(1)T.

Usage Guidelines

This command provides a security mechanism whereby updates from the specified neighbor containing the specified path attributes are “treat-as-withdraw”. Treat-as-withdraw means that the prefixes in that Update are removed from the BGP routing table.

Attribute types 1, 2, 3, 4, 8, 14, 15, and 16 cannot be specified to cause the withdrawal of a prefix. Attribute type 5 (localpref), type 9 (Originator), and type 10 (Cluster-ID) can be specified for withdrawal for eBGP neighbors only.

Configuring this command will trigger an inbound Route Refresh to ensure that the routing table is up to date.

Examples

In the following example, updates from the specified neighbor that contain path attribute 100 or 128 are treat-as-withdraw and the prefixes are withdrawn from the BGP routing table:

router bgp 65000
 neighbor 2001:DB8:1::1 path-attribute treat-as-withdraw 100 in
 neighbor 2001:DB8:1::1 path-attribute treat-as-withdraw 128 in
 

In the following example, updates from the specified neighbor that contain path attributes in the range from 17 to 255 are treat-as-withdraw and the prefixes are withdrawn from the BGP routing table:


router bgp 65000
 neighbor 2001:DB8:1::1 path-attribute treat-as-withdraw range 17 255 in 

Related Commands

Command

Description

neighbor path-attribute discard

Configures the device to discard specific path attributes from Update messages from the specified neighbor.

show ip bgp neighbor

Displays the configured discard and treat-as-withdraw attribute values and counters of incoming Update messages containing those attributes.

show ip bgp path-attribute discard

Displays all prefixes for which an attribute has been discarded.

show ip bgp path-attribute unknown

Displays all prefixes that have an unknown attribute.

show ip bgp vpnv4 all

Displays the unknown attributes and discarded attributes associated with a prefix.

neighbor peer-group (assigning members)

To configure a BGP neighbor to be a member of a peer group, use the neighbor peer-group command in address family or router configuration mode. To remove the neighbor from the peer group, use the noform of this command.

neighbor { ip-address | ipv6-address } peer-group peer-group-name

no neighbor { ip-address | ipv6-address } peer-group peer-group-name

Syntax Description

ip-address

IP address of the BGP neighbor that belongs to the peer group specified by the peer-group-name argument.

ipv6-address

IPv6 address of the BGP neighbor that belongs to the peer group specified by the peer-group-name argument.

peer-group-name

Name of the BGP peer group to which this neighbor belongs.

Command Default

There are no BGP neighbors in a peer group.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

11.0

This command was introduced.

12.0(7)T

Address family configuration mode was added.

12.2(2)T

Support for IPv6 was added.

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Cisco IOS XE Release 2.1

This command was introduced on Cisco ASR 1000 Series Routers.

Usage Guidelines

The neighbor at the IP address indicated inherits all the configured options of the peer group.


Note


Using the no form of the neighbor peer-group command removes all of the BGP configuration for that neighbor, not just the peer group association.


Examples

The following router configuration mode example assigns three neighbors to the peer group named internal:

router bgp 100
 neighbor internal peer-group
 neighbor internal remote-as 100
 neighbor internal update-source loopback 0
 neighbor internal route-map set-med out
 neighbor internal filter-list 1 out
 neighbor internal filter-list 2 in
 neighbor 172.16.232.53 peer-group internal
 neighbor 172.16.232.54 peer-group internal
 neighbor 172.16.232.55 peer-group internal
 neighbor 172.16.232.55 filter-list 3 in

The following address family configuration mode example assigns three neighbors to the peer group named internal:

router bgp 100
address-family ipv4 unicast
 neighbor internal peer-group
 neighbor internal remote-as 100
 neighbor internal update-source loopback 0
 neighbor internal route-map set-med out
 neighbor internal filter-list 1 out
 neighbor internal filter-list 2 in
 neighbor 172.16.232.53 peer-group internal
 neighbor 172.16.232.54 peer-group internal
 neighbor 172.16.232.55 peer-group internal
 neighbor 172.16.232.55 filter-list 3 in

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPNv4 address prefixes.

neighbor peer-group (creating)

Creates a BGP peer group.

neighbor shutdown

Disables a neighbor or peer group.

neighbor peer-group (creating)

To create a BGP or multiprotocol BGP peer group, use the neighbor peer-group command in address family or router configuration mode. To remove the peer group and all of its members, use the noform of this command.

neighbor peer-group-name peer-group

no neighbor peer-group-name peer-group

Syntax Description

peer-group-name

Name of the BGP peer group.

Command Default

There is no BGP peer group.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

11.0

This command was introduced.

11.1(20)CC

The nlri unicast, nlri multicast, and nlri unicast multicast keywords were added.

12.0(2)S

The nlri unicast, nlri multicast, and nlri unicast multicast keywords were added.

12.0(7)T

The nlri unicast, nlri multicast, and nlri unicast multicast keywords were removed.

Address family configuration mode was added.

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

Often in a BGP or multiprotocol BGP speaker, many neighbors are configured with the same update policies (that is, same outbound route maps, distribute lists, filter lists, update source, and so on). Neighbors with the same update policies can be grouped into peer groups to simplify configuration and make update calculation more efficient.


Note


Peer group members can span multiple logical IP subnets, and can transmit, or pass along, routes from one peer group member to another.


Once a peer group is created with the neighbor peer-group command, it can be configured with the neighbor commands. By default, members of the peer group inherit all the configuration options of the peer group. Members also can be configured to override the options that do not affect outbound updates.

All the peer group members will inherit the current configuration as well as changes made to the peer group. Peer group members will always inherit the following configuration options by default:

  • remote-as (if configured)

  • version

  • update-source

  • outbound route-maps

  • outbound filter-lists

  • outbound distribute-lists

  • minimum-advertisement-interval

  • next-hop-self

If a peer group is not configured with a remote-as option, the members can be configured with the neighbor {ip-address | peer-group-name} remote-as command. This command allows you to create peer groups containing external BGP (eBGP) neighbors.

Examples

The following example configurations show how to create these types of neighbor peer group:

  • internal Border Gateway Protocol (iBGP) peer group

  • eBGP peer group

  • Multiprotocol BGP peer group

In the following example, the peer group named internal configures the members of the peer group to be iBGP neighbors. By definition, this is an iBGP peer group because the router bgp command and the neighbor remote-as command indicate the same autonomous system (in this case, autonomous system 100). All the peer group members use loopback 0 as the update source and use set-med as the outbound route map. The neighbor internal filter-list 2 in command shows that, except for 172.16.232.55, all the neighbors have filter list 2 as the inbound filter list.

router bgp 100
 neighbor internal peer-group
 neighbor internal remote-as 100
 neighbor internal update-source loopback 0
 neighbor internal route-map set-med out
 neighbor internal filter-list 1 out
 neighbor internal filter-list 2 in
 neighbor 172.16.232.53 peer-group internal
 neighbor 172.16.232.54 peer-group internal
 neighbor 172.16.232.55 peer-group internal
 neighbor 172.16.232.55 filter-list 3 in

The following example defines the peer group named external-peers without the neighbor remote-as command. By definition, this is an eBGP peer group because each individual member of the peer group is configured with its respective autonomous system number separately. Thus the peer group consists of members from autonomous systems 200, 300, and 400. All the peer group members have the set-metric route map as an outbound route map and filter list 99 as an outbound filter list. Except for neighbor 172.16.232.110, all of them have 101 as the inbound filter list.

router bgp 100
 neighbor external-peers peer-group
 neighbor external-peers route-map set-metric out
 neighbor external-peers filter-list 99 out
 neighbor external-peers filter-list 101 in
 neighbor 172.16.232.90 remote-as 200
 neighbor 172.16.232.90 peer-group external-peers
 neighbor 172.16.232.100 remote-as 300
 neighbor 172.16.232.100 peer-group external-peers
 neighbor 172.16.232.110 remote-as 400
 neighbor 172.16.232.110 peer-group external-peers
 neighbor 172.16.232.110 filter-list 400 in

In the following example, all members of the peer group are multicast-capable:

router bgp 100
neighbor 10.1.1.1 remote-as 1
neighbor 172.16.2.2 remote-as 2
address-family ipv4 multicast
 neighbor mygroup peer-group
 neighbor 10.1.1.1 peer-group mygroup
 neighbor 172.16.2.2 peer-group mygroup
 neighbor 10.1.1.1 activate
 neighbor 172.16.2.2 activate

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPNv4 address prefixes.

clear ip bgp peer-group

Removes all the members of a BGP peer group.

show ip bgp peer-group

Displays information about BGP peer groups.

neighbor prefix-list

To prevent distribution of Border Gateway Protocol (BGP) neighbor information as specified in a prefix list, a Connectionless Network Service (CLNS) filter expression, or a CLNS filter set, use the neighbor prefix-list command in address family or router configuration mode. To remove a filter list, use the no form of this command.

neighbor { ip-address | peer-group-name } prefix-list { prefix-list-name | clns-filter-expr-name | clns-filter-set-name } { in | out }

no neighbor { ip-address | peer-group-name } prefix-list { prefix-list-name | clns-filter-expr-name | clns-filter-set-name } { in | out }

Syntax Description

ip-address

IP address of neighbor.

peer-group-name

Name of a BGP peer group.

prefix-list-name

Name of a prefix list. This argument is used only under router configuration mode.

clns-filter-expr-name

Name of a CLNS filter expression. This argument is used only under network service access point (NSAP) address family configuration mode.

clns-filter-set-name

Name of a CLNS filter set. This argument is used only under NSAP address family configuration mode.

in

Filter list is applied to incoming advertisements from that neighbor.

out

Filter list is applied to outgoing advertisements to that neighbor.

Command Default

All external and advertised address prefixes are distributed to BGP neighbors.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.0

This command was introduced.

12.0(7)T

Address family configuration mode was added.

12.2(8)T

Under address family configuration mode, the prefix-list-nameargument was amended to specify the name of a CLNS filter expression or a CLNS filter set.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SRB

This command was integrated into Cisco IOS Release 12.2(33)SRB.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Cisco IOS XE 2.6

This command was integrated into Cisco IOS XE Release 2.6.

Usage Guidelines

Using prefix lists is one of three ways to filter BGP advertisements. You can also use AS-path filters, defined with the ip as-path access-list global configuration command and used in the neighbor filter-list command to filter BGP advertisements. The third way to filter BGP advertisements uses access or prefix lists with the neighbor distribute-listcommand.

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command. Specifying the command with an IP address will override the value inherited from the peer group.

Use the neighbor prefix-list command in address family configuration mode to filter NSAP BGP advertisements.


Note


Do not apply both a neighbor distribute-list and a neighbor prefix-list command to a neighbor in any given direction (inbound or outbound). These two commands are mutually exclusive, and only one command (neighbor distribute-listor neighbor prefix-list) can be applied to each inbound or outbound direction.


Examples

The following router configuration mode example applies the prefix list named abc to incoming advertisements from neighbor 10.23.4.1:

router bgp 65200
 network 192.168.1.2
 neighbor 10.23.4.1 prefix-list abc in 

The following address family configuration mode example applies the prefix list named abc to incoming advertisements from neighbor 10.23.4.2:

router bgp 65001
address-family ipv4 unicast
 network 192.168.2.4
 neighbor 10.23.4.2 prefix-list abc in 

The following router configuration mode example applies the prefix list named CustomerA to outgoing advertisements to neighbor 10.23.4.3:

router bgp 64800
 network 192.168.3.6
 neighbor 10.23.4.3 prefix-list CustomerA out

The following address family configuration mode example applies the CLNS filter list set named default-prefix-only to outbound advertisements to neighbor 10.1.2.1:

clns filter-set default-prefix-only deny 49...
clns filter-set default-prefix-only permit default
!
router bgp 65202
 address-family nsap
  neighbor 10.1.2.1 activate
  neighbor 10.1.2.1 default-originate
  neighbor 10.1.2.1 prefix-list default-prefix-only out 

Related Commands

Command

Description

address-family ipv4 (BGP)

Enters the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.

address-family vpnv4

Enters the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPNv4 address prefixes.

clear ip prefix-list

Resets the hit count of the prefix list entries.

clns filter-expr

Creates an entry in a CLNS filter expression.

clns filter-set

Creates an entry in a CLNS filter set.

ip as-path access-list

Defines a BGP-related access list.

ip prefix-list

Creates an entry in a prefix list.

ip prefix-list description

Adds a text description of a prefix list.

ip prefix-list sequence-number

Enables the generation of sequence numbers for entries in a prefix list.

neighbor filter-list

Sets up a BGP filter.

show bgp nsap filter-list

Displays information about a filter list or filter list entries.

show ip bgp peer-group

Displays information about BGP peer groups.

show ip prefix-list

Displays information about a prefix list or prefix list entries.

neighbor remote-as

To add an entry to the BGP or multiprotocol BGP neighbor table, use the neighbor remote-as command in router configuration mode. To remove an entry from the table, use the no form of this command.

neighbor { ip-address | ipv6-address% | peer-group-name } remote-as autonomous-system-number [ alternate-as autonomous-system-number ... ]

no neighbor { ip-address | ipv6-address% | peer-group-name } remote-as autonomous-system-number [ alternate-as autonomous-system-number ... ]

Syntax Description

ip-address

IP address of the neighbor.

ipv6-address

IPv6 address of the neighbor.

%

(Optional) IPv6 link-local address identifier. This keyword needs to be added whenever a link-local IPv6 address is used outside the context of its interface.

peer-group-name

Name of a BGP peer group.

autonomous-system-number

Number of an autonomous system to which the neighbor belongs in the range from 1 to 65535.

  • In Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, and later releases, 4-byte autonomous system numbers are supported in the range from 65536 to 4294967295 in asplain notation and in the range from 1.0 to 65535.65535 in asdot notation.

  • In Cisco IOS Release 12.0(32)S12, 12.4(24)T, and Cisco IOS XE Release 2.3, 4-byte autonomous system numbers are supported in the range from 1.0 to 65535.65535 in asdot notation only.

For more details about autonomous system number formats, see the router bgp command.

When used with the alternate-as keyword, up to five autonomous system numbers may be entered.

alternate-as

(Optional) Specifies an alternate autonomous system in which a potential dynamic neighbor can be identified. Up to five autonomous system numbers may be entered when this keyword is specified.

Command Default

There are no BGP or multiprotocol BGP neighbor peers.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

11.0

The peer-group-name argument was added.

11.1(20)CC

The nlri unicast, nlri multicast, and nlri unicast multicast keywords were added.

12.0(7)T

The nlri unicast, nlri multicast, and nlri unicast multicast keywords were removed.

12.2(4)T

Support for the IPv6 address family was added.

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SRB

This command was modified. The % keyword was added.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH. The alternate-as keyword was added to support BGP dynamic neighbors.

12.2(33)SB

This command was integrated into Cisco IOS Release 12.2(33)SB.

Cisco IOS XE Release 2.1

This command was introduced on Cisco ASR 1000 Series Routers.

12.0(32)S12

This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.

12.0(32)SY8

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

12.4(24)T

This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.

Cisco IOS XE Release 2.3

This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.

12.2(33)SXI1

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

12.0(33)S3

This command was modified. Support for asplain notation was added and the default format for 4-byte autonomous system numbers is now asplain.

Cisco IOS XE Release 2.4

This command was modified. Support for asplain notation was added and the default format for 4-byte autonomous system numbers is now asplain.

12.2(33)SRE

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

12.2(33)XNE

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

15.0(1)S

This command was integrated into Cisco IOS Release 15.0(1)S.

15.1(1)SG

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

Cisco IOS XE Release 3.3SG

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

15.1(2)SNG

This command was implemented on the Cisco ASR 901 Series Aggregation Services Routers.

15.2(1)E

This command was integrated into Cisco IOS Release 15.2(1)E.

Usage Guidelines

Specifying a neighbor with an autonomous system number that matches the autonomous system number specified in the router bgp global configuration command identifies the neighbor as internal to the local autonomous system. Otherwise, the neighbor is considered external.

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

By default, neighbors that are defined using the neighbor remote-as command in router configuration mode exchange only unicast address prefixes. To exchange other address prefix types, such as multicast and Virtual Private Network (VPN) Version 4, neighbors must also be activated in the appropriate address family configuration mode.

Use the alternate-as keyword introduced in Cisco IOS Release 12.2(33)SXH to specify up to five alternate autonomous systems in which a dynamic BGP neighbor may be identified. BGP dynamic neighbor support allows BGP peering to a group of remote neighbors that are defined by a range of IP addresses. BGP dynamic neighbors are configured using a range of IP addresses and BGP peer groups. After a subnet range is configured and associated with a BGP peer group using the bgp listen command and a TCP session is initiated for an IP address in the subnet range, a new BGP neighbor is dynamically created as a member of that group. The new BGP neighbor will inherit any configuration or templates for the group.

The % keyword is used whenever link-local IPv6 addresses are used outside the context of their interfaces. This keyword does not need to be used for non-link-local IPv6 addresses.

In Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, and later releases, the Cisco implementation of 4-byte autonomous system numbers uses asplain--65538 for example--as the default regular expression match and output display format for autonomous system numbers, but you can configure 4-byte autonomous system numbers in both the asplain format and the asdot format as described in RFC 5396. To change the default regular expression match and output display of 4-byte autonomous system numbers to asdot format, use the bgp asnotation dot command followed by the clear ip bgp * command to perform a hard reset of all current BGP sessions.

In Cisco IOS Release 12.0(32)S12, 12.4(24)T, and Cisco IOS XE Release 2.3, the Cisco implementation of 4-byte autonomous system numbers uses asdot--1.2 for example--as the only configuration format, regular expression match, and output display, with no asplain support.


Note


In Cisco IOS releases that include 4-byte ASN support, command accounting and command authorization that include a 4-byte ASN number are sent in the asplain notation irrespective of the format that is used on the command-line interface.


To ensure a smooth transition, we recommend that all BGP speakers within an autonomous system that is identified using a 4-byte autonomous system number, be upgraded to support 4-byte autonomous system numbers.

Examples

The following example specifies that a router at the address 10.108.1.2 is an internal BGP (iBGP) neighbor in autonomous system number 65200:

router bgp 65200
 network 10.108.0.0
 neighbor 10.108.1.2 remote-as 65200

The following example specifies that a router at the IPv6 address 2001:0DB8:1:1000::72a is an external BGP (eBGP) neighbor in autonomous system number 65001:

router bgp 65300
 address-family ipv6 vrf site1
 neighbor 2001:0DB8:1:1000::72a remote-as 65001

The following example assigns a BGP router to autonomous system 65400, and two networks are listed as originating in the autonomous system. Then the addresses of three remote routers (and their autonomous systems) are listed. The router being configured will share information about networks 10.108.0.0 and 192.168.7.0 with the neighbor routers. The first router is a remote router in a different autonomous system from the router on which this configuration is entered (an eBGP neighbor); the second neighbor remote-as command shows an internal BGP neighbor (with the same autonomous system number) at address 10.108.234.2; and the last neighbor remote-as command specifies a neighbor on a different network from the router on which this configuration is entered (also an eBGP neighbor).

router bgp 65400
 network 10.108.0.0
 network 192.168.7.0
 neighbor 10.108.200.1 remote-as 65200
 neighbor 10.108.234.2 remote-as 65400
 neighbor 172.29.64.19 remote-as 65300

The following example configures neighbor 10.108.1.1 in autonomous system 65001 to exchange only multicast routes:

router bgp 65001
 neighbor 10.108.1.1 remote-as 65001
 neighbor 172.31 1.2 remote-as 65001
 neighbor 172.16.2.2 remote-as 65002
 address-family ipv4 multicast
  neighbor 10.108.1.1 activate
  neighbor 172.31 1.2 activate
  neighbor 172.16.2.2 activate
  exit-address-family

The following example configures neighbor 10.108.1.1 in autonomous system 65001 to exchange only unicast routes:

router bgp 65001
 neighbor 10.108.1.1 remote-as 65001
 neighbor 172.31 1.2 remote-as 65001
 neighbor 172.16.2.2 remote-as 65002

The following example, configurable only in Cisco IOS Release 12.2(33)SXH and later releases, configures a subnet range of 192.168.0.0/16 and associates this listen range with a BGP peer group. Note that the listen range peer group that is configured for the BGP dynamic neighbor feature can be activated in the IPv4 address family using the neighbor activate command. After the initial configuration on Router 1, when Router 2 starts a BGP router session and adds Router 1 to its BGP neighbor table, a TCP session is initiated, and Router 1 creates a new BGP neighbor dynamically because the IP address of the new neighbor is within the listen range subnet.

Examples

enable
configure terminal
router bgp 45000
 bgp log-neighbor-changes
 neighbor group192 peer-group 
 bgp listen range 192.168.0.0/16 peer-group group192   
 neighbor group192 remote-as 40000 alternate-as 50000
 address-family ipv4 unicast 
 neighbor group192 activate
 end

Examples

enable
configure terminal
router bgp 50000
 neighbor 192.168.3.1 remote-as 45000
 exit

If the show ip bgp summary command is now entered on Router 1, the output shows the dynamically created BGP neighbor, 192.168.3.2.

Router1# show ip bgp summary
BGP router identifier 192.168.3.1, local AS number 45000
BGP table version is 1, main routing table version 1
Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
*192.168.3.2    4 50000       2       2        0    0    0 00:00:37        0
* Dynamically created based on a listen range command
Dynamically created neighbors: 1/(200 max), Subnet ranges: 1
BGP peergroup group192 listen range group members: 
  192.168.0.0/16 

The following example configures a BGP process for autonomous system 65538 and configures two external BGP neighbors in different autonomous systems using 4-byte autonomous system numbers in asplain format. This example is supported only on Cisco IOS Release 12.0(32)SY8, 12.0(33)S3, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, Cisco IOS XE Release 2.4, or later releases.

router bgp 65538
 neighbor 192.168.1.2 remote-as 65536
 neighbor 192.168.3.2 remote-as 65550
 neighbor 192.168.3.2 description finance
 !
 address-family ipv4
  neighbor 192.168.1.2 activate
  neighbor 192.168.3.2 activate
  no auto-summary
  no synchronization
  network 172.17.1.0 mask 255.255.255.0
  exit-address-family

The following example configures a BGP process for autonomous system 1.2 and configures two external BGP neighbors in different autonomous systems using 4-byte autonomous system numbers in asdot format. This example requires Cisco IOS Release 12.0(32)SY8, 12.0(32)S12, 12.2(33)SRE, 12.2(33)XNE, 12.2(33)SXI1, 12.4(24)T, Cisco IOS XE Release 2.3, or a later release.

router bgp 1.2
 neighbor 192.168.1.2 remote-as 1.0
 neighbor 192.168.3.2 remote-as 1.14
 neighbor 192.168.3.2 description finance
 !
 address-family ipv4
  neighbor 192.168.1.2 activate
  neighbor 192.168.3.2 activate
  no auto-summary
  no synchronization
  network 172.17.1.0 mask 255.255.255.0
  exit-address-family

Related Commands

Command

Description

bgp asnotation dot

Changes the default display and the regular expression match format of BGP 4-byte autonomous system numbers from asplain (decimal values) to dot notation.

bgp listen

Associates a subnet range with a BGP peer group and activates the BGP dynamic neighbors feature.

neighbor peer-group

Creates a BGP peer group.

router bgp

Configures the BGP routing process.

neighbor remove-private-as

To remove private autonomous system numbers from the autonomous system path (a list of autonomous systems that a route passes through to reach a BGP peer) in eBGP outbound routing updates, use the neighbor remove-private-as command in router configuration, address family configuration, or peer-group template mode. To disable this function, use the no form of this command.

neighbor { ip-address | peer-group-name } remove-private-as [ all [replace-as] ]

no neighbor { ip-address | peer-group-name } remove-private-as

Syntax Description

ip-address

IP address of the BGP-speaking neighbor.

peer-group-name

Name of a BGP peer group.

all

(Optional) Removes all private AS numbers from the AS path in outgoing updates.

replace-as

(Optional) As long as the all keyword is specified, the replace-as keyword causes all private AS numbers in the AS path to be replaced with the router’s local AS number.

Command Default

No private AS numbers are removed from the AS path.

Command Modes

Router configuration (config-router)

Address family configuration (config-router-af) [Release 15.1(2)T and later]

Peer-group template [Release 15.1(2)T and later]

Command History

Release

Modification

10.3

This command was introduced.

11.0

The peer-group-name argument was added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

15.1(2)T

This command was modified. The all keyword and the replace-as keyword were added.

15.0(1)S

This command was integrated into Cisco IOS Release 15.0(1)S.

Cisco IOS XE Release 3.1S

This command was integrated into Cisco IOS XE Release 3.1S.

15.1(1)SY

This command was integrated into Cisco IOS Release 15.1(1)SY.

Usage Guidelines

This command is available for external BGP (eBGP) neighbors only. The private AS values are 64512 to 65535.

When an update is passed to the external neighbor, if the AS path includes private AS numbers, the software will drop the private AS numbers.

Behavior Before Release 15.1(2)T

  • If the AS path includes both private and public AS numbers, the software considers this to be a configuration error and does not remove the private AS numbers.

  • If the AS path contains the AS number of the eBGP neighbor, the private AS numbers are not removed.

  • If this command is used with confederation, it will work as long as the private AS numbers follow the confederation portion of the AS path.

Behavior in Release 15.1(2)T and Later

  • The neighbor remove-private-as command removes private AS numbers from the AS path even if the path contains both public and private ASNs.

  • The neighbor remove-private-as command removes private AS numbers even if the AS path contains only private AS numbers. There is no likelihood of a 0-length AS path because this command can be applied to eBGP peers only, in which case the AS number of the local router is appended to the AS path.

  • The neighbor remove-private-as command removes private AS numbers even if the private ASNs appear before the Confederation segments in the AS path.

  • Upon removing private AS numbers from the AS path, the path length of prefixes being sent out will decrease. Because the AS path length is a key element of BGP best path selection, it might be necessary to retain the path length. The replace-as keyword ensures that the path length is retained by replacing all removed AS numbers with the local router’s AS number.

  • The feature can be applied to neighbors per address family. Therefore, you can apply the feature to a neighbor in one address family and not in another, affecting update messages on the outbound side for only the address family for which the feature is configured.

Examples

The following example shows a configuration that removes the private AS number from the updates sent to 172.16.2.33. The result is that the AS path for the paths advertised by 10.108.1.1 through AS 100 will contain only “100” (as seen by autonomous system 2051).

router bgp 100 
 neighbor 10.108.1.1 description peer with private-as 
 neighbor 10.108.1.1 remote-as 65001 
 neighbor 172.16.2.33 description eBGP peer 
 neighbor 172.16.2.33 remote-as 2051 
 neighbor 172.16.2.33 remove-private-as 
Router-in-AS100# show ip bgp 10.0.0.0 
BGP routing table entry for 10.0.0.0/8, version 15 
Paths: (1 available, best #1) 
  Advertised to non peer-group peers: 
    172.16.2.33 
  65001 
    10.108.1.1 from 10.108.1.1 
      Origin IGP, metric 0, localpref 100, valid, external, best 
Router-in-AS2501# show ip bgp 10.0.0.0 
BGP routing table entry for 10.0.0.0/8, version 3 
Paths: (1 available, best #1) 
  Not advertised to any peer 
  2 
    172.16.2.32 from 172.16.2.32 
      Origin IGP, metric 0, localpref 100, valid, external, best 

The following is an example of removing and replacing private ASNs using Cisco IOS Release 15.1(2)T or later. In this example, when Router A sends prefixes to the peer 172.30.0.7, all private ASNs in the AS path are replaced with the router’s own ASN, which is 100.

Examples

router bgp 100
 bgp log-neighbor-changes
 neighbor 172.16.101.1 remote-as 1001
 neighbor 172.16.101.1 update-source Loopback0
 neighbor 172.30.0.7 remote-as 200
 neighbor 172.30.0.7 remove-private-as all replace-as
 no auto-summary

Router A receives 1.1.1.1 from peer 172.16.101.1, which has some private ASNs (65200, 65201, and 65201) in the AS path list, as shown in the following output:

RouterA# show ip bgp 1.1.1.1

BGP routing table entry for 1.1.1.1/32, version 2
Paths: (1 available, best #1, table default)
   Advertised to update-groups:
      1          2
   1001 65200 65201 65201 1002 1003 1003
     172.16.101.1 from 172.16.101.1 (172.16.101.1)
       Origin IGP, localpref 100, valid, external, best RouterA#

Because Router A is configured with neighbor 172.30.0.7 remove-private-as all replace-as, Router A sends prefix 1.1.1.1 with all private ASNs replaced with 100:

Examples

RouterB# show ip bgp 1.1.1.1

BGP routing table entry for 1.1.1.1/32, version 3
Paths: (1 available, best #1, table default)
   Not advertised to any peer
   100 1001 100 100 100 1002 1003 1003
     172.30.0.6 from 172.30.0.6 (192.168.1.2)
       Origin IGP, localpref 100, valid, external, best RouterB#

Examples

router bgp 200
 bgp log-neighbor-changes
 neighbor 172.30.0.6 remote-as 100
 no auto-summary

Related Commands

Command

Description

neighbor remote-as

Allows entries to the BGP neighbor table.

show ip bgp neighbor

Displays entries in the BGP routing table.

show ip bgp update-group

Displays entries in the BGP routing table.

neighbor route-map

To apply a route map to incoming or outgoing routes, use the neighbor route-map command in address family or router configuration mode. To remove a route map, use the no form of this command.

neighbor { ip-address | peer-group-name | ipv6-address [ % ] } route-map map-name { in | out }

no neighbor { ip-address | peer-group-name | ipv6-address [ % ] } route-map map-name { in | out }

Syntax Description

ip-address

IP address of the neighbor.

peer-group-name

Name of a BGP or multiprotocol BGP peer group.

ipv6-address

IPv6 address of the neighbor.

%

(Optional) IPv6 link-local address identifier. This keyword needs to be added whenever a link-local IPv6 address is used outside the context of its interface.

map-name

Name of a route map.

in

Applies route map to incoming routes.

out

Applies route map to outgoing routes.

Command Default

No route maps are applied to a peer.

Command Modes

Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

12.0(7)T

Address family configuration mode was added.

12.2(4)T

Support for IPv6 was added.

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SRB

The % keyword was added.

12.2(33)SB

This command was integrated into Cisco IOS Release 12.2(33)SB.

Cisco IOS XE Release 2.1

This command was introduced on Cisco ASR 1000 Series Routers.

12.2(33)SXI

This command was integrated into Cisco IOS Release 12.2(33)SXI.

Usage Guidelines

When specified in address family configuration mode, this command applies a route map to that particular address family only. When specified in router configuration mode, this command applies a route map to IPv4 or IPv6 unicast routes only.

If an outbound route map is specified, it is proper behavior to only advertise routes that match at least one section of the route map.

If you specify a BGP or multiprotocol BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command. Specifying the command for a neighbor overrides the inbound policy that is inherited from the peer group.

The % keyword is used whenever link-local IPv6 addresses are used outside the context of their interfaces. This keyword does not need to be used for non-link-local IPv6 addresses.

Examples

The following router configuration mode example applies a route map named internal-map to a BGP incoming route from 172.16.70.24:

router bgp 5
 neighbor 172.16.70.24 route-map internal-map in
route-map internal-map
 match as-path 1
 set local-preference 100

The following address family configuration mode example applies a route map named internal-map to a multiprotocol BGP incoming route from 172.16.70.24:

router bgp 5
address-family ipv4 multicast
 neighbor 172.16.70.24 route-map internal-map in
route-map internal-map
 match as-path 1
 set local-preference 100

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IP Version 4 address prefixes.

address-family ipv6

Enters address family configuration mode for configuring routing sessions such as BGP that use standard IPv6 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPN Version 4 address prefixes.

address-family vpnv6

Places the router in address family configuration mode for configuring routing sessions that use standard VPNv6 address prefixes.

neighbor remote-as

Creates a BGP peer group.

neighbor route-reflector-client

To configure the router as a BGP route reflector and configure the specified neighbor as its client, use the neighbor route-reflector-client command in address family or router configuration mode. To indicate that the neighbor is not a client, use the no form of this command.

neighbor { ip-address | ipv6-address | peer-group-name } route-reflector-client

no neighbor { ip-address | ipv6-address | peer-group-name } route-reflector-client

Syntax Description

ip-address

IP address of the BGP neighbor being identified as a client.

ipv6-address

IPv6 address of the BGP neighbor being identified as a client.

peer-group-name

Name of a BGP peer group.

Command Default

There is no route reflector in the autonomous system.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

11.1

This command was introduced.

12.0(7)T

Address family configuration mode was added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SRB

This command was modified. The ipv6-address and peer-group-name arguments were added.

12.2(33)SB

This command was integrated into Cisco IOS Release 12.2(33)SB.

12.2(33)SXI

This command was integrated into Cisco IOS Release 12.2(33)SXI.

Cisco IOS XE Release 3.1S

This command was integrated into Cisco IOS XE Release 3.1S.

Usage Guidelines

By default, all internal BGP (iBGP) speakers in an autonomous system must be fully meshed, and neighbors do not readvertise iBGP learned routes to neighbors, thus preventing a routing information loop. When all the clients are disabled, the local router is no longer a route reflector.

If you use route reflectors, all iBGP speakers need not be fully meshed. In the route reflector model, an Internal BGP peer is configured to be a route reflector responsible for passing iBGP learned routes to iBGP neighbors. This scheme eliminates the need for each router to talk to every other router.

Use the neighbor route-reflector-client command to configure the local router as the route reflector and the specified neighbor as one of its clients. All the neighbors configured with this command will be members of the client group and the remaining iBGP peers will be members of the nonclient group for the local route reflector.

The bgp client-to-client reflection command controls client-to-client reflection.

Examples

In the following router configuration mode example, the local router is a route reflector. It passes learned iBGP routes to the neighbor at 172.16.70.24.

router bgp 5
 neighbor 172.16.70.24 route-reflector-client

In the following address family configuration mode examples, the local router is a route reflector. It passes learned iBGP routes to the neighbor at 172.16.70.24.

router bgp 5
address-family ipv4 unicast
 neighbor 172.16.70.24 route-reflector-client

router bgp 5
address-family l2vpn evpn
 neighbor 172.16.70.24 route-reflector-client

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.

address-family ipv6

Enters address family configuration mode for configuring routing sessions such as BGP that use standard IPv6 address prefixes.

address-family l2vpn

Enters address family configuration mode for configuring routing sessions using Layer 2 Virtual Private Network (L2VPN) endpoint provisioning address information.

address-family vpnv6

Places the router in address family configuration mode for configuring routing sessions such as BGP that use standard VPNv6 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPNv4 address prefixes.

address-family vpnv6

Places the router in address family configuration mode for configuring routing sessions such as BGP that use standard VPNv6 address prefixes.

bgp client-to-client reflection

Restores route reflection from a BGP route reflector to clients.

bgp cluster-id

Configures the cluster ID if the BGP cluster has more than one route reflector.

show bgp ipv6

Displays entries in the IPv6 BGP routing table.

show ip bgp

Displays entries in the BGP routing table.

neighbor route-server-client

To specify on a BGP route server that a neighbor is a route server client, use the neighbor route-server-client command in IPv4 or IPv6 address family configuration mode. To remove that neighbor as a route server client, use the no form of this command.

neighbor { ipv4-address | ipv6-address } route-server-client [ context context-name ]

no neighbor { ipv4-address | ipv6-address } route-server-client [ context context-name ]

Syntax Description

ipv4-address

IPv4 address of a BGP neighbor.

ipv6-address

IPv6 address of a BGP neighbor.

context context-name

(Optional) Assigns a route server context to the specified neighbor. Specify the name of a route server context, which you configure in the route-server-context command, when you want flexible policy handling.

Command Default

There are no BGP route servers or BGP route server clients.

Command Modes


IPv4 or IPv6 address family configuration (config-router-af)

Command History

Release

Modification

Cisco IOS XE 3.3S

This command was introduced.

15.2(3)T

This command was integrated into Cisco IOS Release 15.2(3)T.

Usage Guidelines

Use this command on a BGP route server to specify the neighbors that are route server clients.

If you want to configure flexible policy handling, you must create a route server context, which includes an import map. The import map points to a route map. The route map points to one or more match commands. The match command in the example below matches on autonomous system numbers by pointing to an access list. The access list is configured with at least one permit statement. The access list that is based on autonomous system numbers is configured by the ip as-path access-list command.

Examples

In the following example, the local router is a BGP route server. Its neighbors at 10.0.0.1 and 10.0.0.5 are its route server clients. This example enables basic route server functionality (nexthop, AS-path, and MED transparency).

router bgp 900
 neighbor 10.0.0.1 remote-as 100
 neighbor 10.0.0.5 remote-as 500
 address-family ipv4 unicast
 neighbor 10.0.0.1 route-server-client
 neighbor 10.0.0.5 route-server-client
 neighbor 10.0.0.1 activate
 neighbor 10.0.0.5 activate

In the following example, the local router is a BGP route server. Its neighbors at 10.10.10.12 and 10.10.10.13 are its route server clients. A route server context named ONLY_AS27_CONTEXT is created and applied to the neighbor at 10.10.10.13. The context uses an import map that references a route map named only_AS27_routemap. The route map matches routes permitted by access list 27. Access list 27 permits routes that have 27 in the autonomous system path.

router bgp 65000
   route-server-context ONLY_AS27_CONTEXT
      address-family ipv4 unicast
         import-map only_AS27_routemap
      exit-address-family
   exit-route-server-context
   !
   neighbor 10.10.10.12 remote-as 12
   neighbor 10.10.10.12 description Peer12
   neighbor 10.10.10.13 remote-as 13
   neighbor 10.10.10.13 description Peer13
   neighbor 10.10.10.21 remote-as 21
   neighbor 10.10.10.27 remote-as 27
   !
   address-family ipv4
      neighbor 10.10.10.12 activate
      neighbor 10.10.10.12 route-server-client
      neighbor 10.10.10.13 activate
      neighbor 10.10.10.13 route-server-client context ONLY_AS27_CONTEXT
      neighbor 10.10.10.21 activate
      neighbor 10.10.10.27 activate
   exit-address-family
!
ip as-path access-list 27 permit 27
!
route-map only_AS27_routemap permit 10
   match as-path 27
!

Related Commands

Command

Description

route-server-context

Creates a route-server context in order to provide flexible policy handling for a BGP route server

neighbor send-community

To specify that a communities attribute should be sent to a BGP neighbor, use the neighbor send-community command in address family or router configuration mode. To remove the entry, use the no form of this command.

neighbor { ip-address | ipv6-address | peer-group-name } send-community [ both | standard | extended ]

no neighbor { ip-address | ipv6-address | peer-group-name } send-community

Syntax Description

ip-address

IP address of the neighbor.

ipv6-address

IPv6 address of the neighbor.

peer-group-name

Name of a BGP peer group.

both

(Optional) Specifies that both standard and extended communities will be sent.

standard

(Optional) Specifies that only standard communities will be sent.

extended

(Optional) Specifies that only extended communities will be sent.

Command Default

No communities attribute is sent to any neighbor.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

10.3

This command was introduced.

11.0

The peer-group-name argument was added.

12.0(7)T

Address family configuration mode was added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SRB

The ipv6-address argument was added.

12.2(33)SB

This command was integrated into Cisco IOS Release 12.2(33)SB.

12.2(33)SXI

This command was integrated into Cisco IOS Release 12.2(33)SXI.

Cisco IOS XE Release 3.7S

This command was integrated into Cisco IOS XE Release 3.7S.

15.1(2)SNG

This command was implemented on the Cisco ASR 901 Series Aggregation Services Routers.

Usage Guidelines

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

Examples

In the following router configuration mode example, the router belongs to autonomous system 109 and is configured to send the communities attribute to its neighbor at IP address 172.16.70.23:

router bgp 109
 neighbor 172.16.70.23 send-community

In the following address family configuration mode example, the router belongs to autonomous system 109 and is configured to send the communities attribute to its neighbor at IP address 172.16.70.23:

router bgp 109
address-family ipv4 multicast
 neighbor 172.16.70.23 send-community

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IP Version 4 address prefixes.

address-family ipv6

Places the router in address family configuration mode for configuring routing sessions such as BGP that use standard IPv6 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPN Version 4 address prefixes.

address-family vpnv6

Places the router in address family configuration mode for configuring routing sessions, such as BGP, that use standard VPNv6 address prefixes.

match community

Matches a BGP community.

neighbor remote-as

Creates a BGP peer group.

set community

Sets the BGP communities attribute.

neighbor shutdown

To disable a neighbor or peer group or to gracefully shut down a link for maintenance, use the neighbor shutdown command in router configuration mode or address family configuration mode. To reenable the neighbor or peer group, use the no form of this command.

neighbor { ip-address | peer-group-name } shutdown graceful seconds [ community value] [ local-preference value ] [ community value ] [ local-preference value]

no neighbor { ip-address | peer-group-name } shutdown graceful seconds [ community value] [ local-preference value ] [ community value ] [ local-preference value]

Syntax Description

ip-address

IP address of the neighbor.

peer-group-name

Name of a BGP peer group.

graceful

(Optional) Configures BGP graceful shutdown, and advertises the route with the GSHUT community and the other community, if specified.

seconds

(Optional) Number of seconds in which BGP graceful shutdown will occur.

  • Range is 30 to 65535 seconds.

  • Configure adequate time to allow iBGP peers to converge and to choose an alternate path as the best path.

community

Specifies whether another community value needs to added or not.

value

Specifies whether a value needs to added or not.

  • The GSHUT community is set by default. You may specify a community other than the GSHUT community, which the receiving router can use to apply a routing policy. Number from 1-4294967295.

local-preference

Advertises the route with the GSHUT community and the specified local preference value.

value

Value of the local preference assigned to routes to the neighbor.

  • The range is from 1 to 4294967295.

Command Default

No change is made to the status of any BGP neighbor or peer group.

Command Modes

Router configuration (config-router)

Address family configuration (config-router-af)

Command History

Release

Modification

12.0

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

15.2(2)S

This command was modified. The graceful seconds keyword and argument, the community value keyword and argument, and the local-preference value keyword and argument were added.

Cisco IOS XE 3.6S

This command was modified. The graceful seconds keyword and argument, the community value keyword and argument, and the local-preference value keyword and argument were added.

Cisco IOS XE 3.7S

This command was implemented on the Cisco ASR 903 router.

15.2(4)M

This command was integrated into Cisco IOS Release 15.2(4)M.

15.2(4)S

This command was implemented on the Cisco 7200 series router.

Usage Guidelines

The neighbor shutdown command terminates any active session for the specified neighbor or peer group and removes all associated routing information. In the case of a peer group, a large number of peering sessions could be terminated suddenly.

To display a summary of BGP neighbors and peer group connections, use the show ip bgp summary command. Those neighbors with an Idle status and the Admin entry have been disabled by the neighbor shutdown command.

“State/PfxRcd” shows the current state of the BGP session or the number of prefixes the router has received from a neighbor or peer group. When the maximum number (as set by the neighbor maximum-prefix command) is reached, the string “PfxRcd” appears in the entry, the neighbor is shut down, and the connection is idle.

BGP Graceful Shutdown

Use the BGP Graceful Shutdown feature to shut down a link for planned, manual, maintenance operations and thereby reduce or eliminate packet loss. The feature can be configured globally (for all address families) or for the IPv4 VRF or IPv6 VRF address family.

Keep in mind that you should configure adequate time to allow iBGP peers to converge and to choose an alternate path as the best path. BGP will not prevent a network administrator from specifying too low a number of seconds, in which case there might not be enough time for graceful shutdown to occur.

If you use the graceful keyword, you must also configure at least one of the community or local-preference keywords. You may use both the community and local-preference keywords.

During graceful shutdown timer, there is no nvgen. There will be nvgen of the neighbor shutdown command only after the shutdown.

neighbor ip-address shutdown graceful seconds local-pref value community value

Once the graceful shutdown timer expires, the command will be nvgened as follows:

neighbor ip-address shutdown

If you reset the sessions using the clear ip bgp command, all timers will be reset. Therefore, there will be no graceful shutdown.

Examples

The following example disables any active session for the neighbor 172.16.70.23:

neighbor 172.16.70.23 shutdown

The following example disables all peering sessions for the peer group named internal:

neighbor internal shutdown

The following example configures the specified neighbor to be gracefully shut down in 1200 seconds and advertises the route with the well-known GSHUT community and a local preference of 400:

neighbor 2001:db8:a::1 shutdown graceful 1200 local-preference 400

Related Commands

Command

Description

ip community-list

Creates a BGP community list.

neighbor maximum-prefix

Controls how many prefixes can be received from a neighbor.

show ip bgp community

Displays the neighbors that belong to various communities.

show ip bgp summary

Displays the status of all BGP connections.

neighbor slow-peer detection

To specify a threshold time that dynamically determines a slow peer, use the neighbor slow-peer detection command in address-family configuration mode. To remove dynamic slow peer detection for a neighbor, use the no form of this command.

neighbor { neighbor-address | peer-group-name } slow-peer detection [ disable | threshold seconds ]

no neighbor { neighbor-address | peer-group-name } slow-peer detection

Syntax Description

neighbor-address

IP address of a BGP neighbor whose update messages are being compared to the current time to determine slowness.

peer-group-name

Peer group name of the bgp neighbors whose update messages are being compared to the current time to determine slowness.

disable

(Optional) Disables slow peer detection for the specified neighbor even if slow peer detection is enabled at the global, address-family level.

threshold seconds

(Optional) Threshold time in seconds that the timestamp of the oldest message in a peers queue can be lagging behind the current time before the peer is determined to be a slow peer. The range is from 120 to 3600; the default is 300.

Command Default

No neighbor is configured as a dynamic slow peer.

Command Modes


Address-family configuration (config-router-af)

Command History

Release

Modification

15.0(1)S

This command was introduced.

Cisco IOS XE 3.1S

This command was introduced.

Usage Guidelines

Update messages are timestamped when they are formatted. The timestamp of the oldest message in a peers queue is compared to the current time to determine if the peer is lagging more than the configured number of seconds. When a peer is dynamically detected to be a slow peer, the system will send a syslog message. The peer will be marked as recovered and another syslog message will be generated only after the peer’s update group converges.

You can use this command alone just to detect a slow peer, or you can use this command with the neighbor slow-peer split-update-group dynamic command to move the peer to a slow update group.


Note


The neighbor slow-peer detection command performs the same function as the bgp slow-peer detection command (at the address-family level). The neighbor slow-peer detection command overrides the global, address-family level command. If the neighbor slow-peer detection command is unconfigured or if no neighbor slow-peer detection is configured, the system will inherit the global, address-family level configuration.



Note


The slow-peer detection command performs the same function through a peer policy template.


Examples

The following example sets a threshold of 400 seconds for the BGP peer at 10.4.4.4. Once the current time is more than 400 seconds later than the timestamp on the oldest message in that peers queue, the peer is determined to be a slow peer.

Router(config-router)# address-family ipv4
Router(config-router-af)# neighbor 10.4.4.4 slow-peer detection threshold 400
Router(config-router-af)# neighbor 10.4.4.4 slow-peer split-update-group dynamic

In the following example, both neighbors 4.4.4.4 and 6.6.6.6 have slow peer detection enabled for them due to the global command bgp slow-peer detection:

Router(config)# router bgp 100
Router(config-router)# bgp log-neighbor-changes
Router(config-router)# neighbor 4.4.4.4 remote-as 100
Router(config-router)# neighbor 6.6.6.6 remote-as 100
Router(config-router)# address-family ipv4
Router(config-router-af)# bgp slow-peer detection
Router(config-router-af)# neighbor 4.4.4.4 activate
Router(config-router-af)# neighbor 6.6.6.6 activate
Router(config-router-af)# no auto-summary
Router(config-router-af)# exit-address-family
Router(config-router)# 

To disable slow peer detection for a particular peer, use the disable keyword. The following example disables slow peer detection for the neighbor 4.4.4.4:

Router(config)# router bgp 100
Router(config-router)# bgp log-neighbor-changes
Router(config-router)# neighbor 4.4.4.4 remote-as 100
Router(config-router)# neighbor 6.6.6.6 remote-as 100
Router(config-router)# address-family ipv4
Router(config-router-af)# bgp slow-peer detection
Router(config-router-af)# neighbor 4.4.4.4 activate
Router(config-router-af)# neighbor 4.4.4.4 slow-peer detection disable
Router(config-router-af)# neighbor 6.6.6.6 activate
Router(config-router-af)# no auto-summary
Router(config-router-af)# exit-address-family
Router(config-router)# 

Related Commands

Command

Description

bgp slow-peer detection

Specifies a threshold time that dynamically determines a slow peer at the global, address family level.

clear ip bgp slow

Moves dynamically configured slow peers back to their original update groups.

neighbor slow-peer split-update-group dynamic

Moves a dynamically detected slow peer to a slow update group.

neighbor slow-peer split-update-group dynamic

To move a dynamically detected slow peer to a slow update group, use the neighbor slow-peer split-update-group dynamiccommand in address-family configuration mode. To cancel this method of moving dynamically detected slow peers to a slow update group, use the no form of this command.

neighbor { neighbor-address | peer-group-name } slow-peer split-update-group dynamic [ permanent | disable ]

no neighbor { neighbor-address | peer-group-name } slow-peer split-update-group dynamic

Syntax Description

neighbor-address

IP address of a BGP neighbor peer that is moved to the slow peer group if dynamically determined to be slow.

peer-group-name

Peer group name of the BGP neighbor peers that are moved to the slow peer group if dynamically determined to be slow.

permanent

(Optional) Specifies that after the slow peer becomes a regular peer (converges), it is not moved back to its original update group automatically. The network administrator can use one of the clear commands to move the peer to its original update group.

disable

(Optional) Disables slow peer protection for the specified neighbor even if slow peer protection is enabled at the global, address-family level.

Command Default

No dynamically detected slow peer is moved to a slow peer update group.

Command Modes


Address-family configuration (config-router-af)

Command History

Release

Modification

15.0(1)S

This command was introduced.

Cisco IOS XE 3.1S

This command was introduced.

Usage Guidelines

When a peer is dynamically detected to be a slow peer, the slow peer is moved to a slow update group. If a static slow peer update group exists, the dynamic slow peer is moved to the static slow peer update group; otherwise, a new slow peer updated group is created and the peer is moved to that group.

  • If the permanent keyword is not configured, the slow peer will be moved back to its regular original update group after it becomes a regular peer (converges).

  • If the permanent keyword is configured, the peer is not automatically moved to its original update group. You can use one of the clear commands to move the peer back to its original update group.

If no slow peer detection is configured, the detection will be done at the default threshold of 300 seconds.

The neighbor slow-peer-split-update-group dynamic command will override the global configuration. However, if the no neighbor slow-peer-split-update-group dynamic command is configured, then the peers will inherit the global address family configuration specified by the bgp slow-peer detection command.

Examples

In the following example, the timestamp of the oldest message in a peers queue is compared to the current time to determine if the peer is lagging more than 360 seconds. If it is, the neighbor who sent the message is determined to be a slow peer, and is put in the slow peer update group. Because the permanent keyword is not configured, the slow peer will be moved back to its regular original update group after it becomes a regular peer (converges).

Router(config-router)# address-family ipv4
Router(config-router-af)# neighbor 10.4.4.4 slow-peer detection threshold 360
Router(config-router-af)# neighbor 10.4.4.4 slow-peer split-update-group dynamic

In the following example, both neighbors 4.4.4.4 and 6.6.6.6 have slow peer protection enabled for them due to the global command bgp slow-peer split-update-group dynamic:

Router(config)# router bgp 100
Router(config-router)# bgp log-neighbor-changes
Router(config-router)# neighbor 4.4.4.4 remote-as 100
Router(config-router)# neighbor 6.6.6.6 remote-as 100
Router(config-router)# address-family ipv4
Router(config-router-af)# bgp slow-peer split-update-group dynamic
Router(config-router-af)# neighbor 4.4.4.4 activate
Router(config-router-af)# neighbor 6.6.6.6 activate
Router(config-router-af)# no auto-summary
Router(config-router-af)# exit-address-family
Router(config-router)# 

To disable slow peer protection for a particular peer, use the disable keyword. The following example disables slow peer protection for the neighbor 4.4.4.4:

Router(config)# router bgp 100
Router(config-router)# bgp log-neighbor-changes
Router(config-router)# neighbor 4.4.4.4 remote-as 100
Router(config-router)# neighbor 6.6.6.6 remote-as 100
Router(config-router)# address-family ipv4
Router(config-router-af)# bgp slow-peer detection
Router(config-router-af)# neighbor 4.4.4.4 activate
Router(config-router-af)# neighbor 4.4.4.4 slow-peer split-update-group dynamic disable
Router(config-router-af)# neighbor 6.6.6.6 activate
Router(config-router-af)# no auto-summary
Router(config-router-af)# exit-address-family
Router(config-router)# 

Related Commands

Command

Description

clear ip bgp slow

Moves dynamically configured slow peers back to their original update groups.

neighbor slow-peer detection

Specifies a threshold time that dynamically determines a slow peer in neighbor address family configuration mode.

neighbor slow-peer split-update-group static

To mark a BGP neighbor as a slow peer and move it to a slow update group, use the neighbor slow-peer split-update-group staticcommand in address-family configuration mode. To unmark the slow peer and return it to its original update group, use the no form of this command.

neighbor { neighbor-address | peer-group-name } slow-peer split-update-group static

no neighbor { neighbor-address | peer-group-name } slow-peer split-update-group static

Syntax Description

neighbor-address

IP address of a BGP neighbor peer that is marked as slow and moved to a slow peer group.

peer-group-name

Peer group name of the BGP neighbor peers that are marked as slow and moved to a slow peer group.

Command Default

No peer is statically marked as slow and moved to a slow peer update group, unless through a peer policy template or configured at neighbor or peer group.

Command Modes


Address-family configuration (config-router-af)

Command History

Release

Modification

15.0(1)S

This command was introduced.

Cisco IOS XE 3.1S

This command was introduced.

Usage Guidelines

Configure a static slow peer when the peer is known to be slow (perhaps due to a slow link or low processing power).

The slow-peer split-update-group staticcommand performs the same function through a peer policy template.

Examples

In the following example, the neighbor with the specified IP address is marked as a slow peer and is moved to a slow update group.

Router(config-router)# address-family ipv4
Router(config-router-af)# neighbor 172.20.2.2 slow-peer split-update-group static

Related Commands

Command

Description

slow-peer split-update-group static

Marks a BGP neighbor as a static slow peer and moves it to a slow update group.

neighbor soft-reconfiguration

To configure the Cisco IOS software to start storing updates, use the neighbor soft-reconfiguration command in router configuration mode. To not store received updates, use the noform of this command.

neighbor { ip-address | peer-group-name } soft-reconfiguration inbound

no neighbor { ip-address | peer-group-name } soft-reconfiguration inbound

Syntax Description

ip-address

IP address of the BGP-speaking neighbor.

peer-group-name

Name of a BGP peer group.

inbound

Indicates that the update to be stored is an incoming update.

Command Default

Soft reconfiguration is not enabled.

Command Modes


Router configuration (config-router)

Command History

Release

Modification

11.2

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

Entering this command starts the storage of updates, which is required to do inbound soft reconfiguration. Outbound BGP soft reconfiguration does not require inbound soft reconfiguration to be enabled.

To use soft reconfiguration, or soft reset, without preconfiguration, both BGP peers must support the soft route refresh capability, which is advertised in the open message sent when the peers establish a TCP session. Routers running Cisco IOS software releases prior to Release 12.1 do not support the route refresh capability and must clear the BGP session using the neighbor soft-reconfiguration command. Clearing the BGP session using the neighbor soft-reconfiguration command has a negative effect on network operations and should only be used as a last resort. Routers running Cisco IOS software Release 12.1 or later releases support the route refresh capability and dynamic soft resets, and can use the clear ip bgp{*| address| peer-group name} in command to clear the BGP session.

To determine whether a BGP router supports this capability, use the show ip bgp neighborscommand. If a router supports the route refresh capability, the following message is displayed:

Received route refresh capability from peer.

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

Examples

The following example enables inbound soft reconfiguration for the neighbor 10.108.1.1. All the updates received from this neighbor will be stored unmodified, regardless of the inbound policy. When inbound soft reconfiguration is done later, the stored information will be used to generate a new set of inbound updates.

router bgp 100
 neighbor 10.108.1.1 remote-as 200
 neighbor 10.108.1.1 soft-reconfiguration inbound

Related Commands

Command

Description

clear ip bgp

Resets a BGP connection using BGP soft reconfiguration.

neighbor remote-as

Creates a BGP peer group.

show ip bgp neighbors

Display information about the TCP and BGP connections to neighbors.

neighbor soo

To set the site-of-origin (SoO) value for a Border Gateway Protocol (BGP) neighbor or peer group, use the neighbor soo command in address family IPv4 VRF configuration mode. To remove the SoO value for a BGP neighbor or peer group, use the no form of this command.

neighbor { ip-address | peer-group-name } soo extended-community-value

no neighbor { ip-address | peer-group-name } soo

Syntax Description

ip-address

IP address of a neighboring router.

peer-group-name

Name of a BGP peer group.

extended-community-value

Specifies the VPN extended community value. The value takes one of the following formats:

  • A 16-bit autonomous system number, a colon, and a 32-bit number, for example: 45000:3

  • A 32-bit IP address, a colon, and a 16-bit number, for example: 192.168.10.2:51

In Cisco IOS Release 12.4(24)T, 4-byte autonomous system numbers are supported in the range from 1.0 to 65535.65535 in asdot notation only.

In Cisco IOS XE Release 2.4, and later releases, 4-byte autonomous system numbers are supported in the range from 65536 to 4294967295 in asplain notation and in the range from 1.0 to 65535.65535 in asdot notation.

For more details about autonomous system number formats, see the router bgp command.

Command Default

No SoO value is set for a BGP neighbor or peer group.

Command Modes


Address family IPv4 VRF configuration (config-router-af)

Command History

Release

Modification

12.4(11)T

This command was introduced.

12.2(33)SRB

This command was integrated into Cisco IOS Release 12.2(33)SRB.

12.2(33)SB

This command was integrated into Cisco IOS Release 12.2(33)SB.

12.4(24)T

This command was modified. Support for 4-byte autonomous system numbers in asdot notation only was added.

Cisco IOS XE Release 2.4

This command was modified. Support for asplain notation was added and the default format for 4-byte autonomous system numbers is now asplain.

12.2(33)SRE

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

12.2(33)XNE

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

15.0(1)SY

This command was integrated into Cisco IOS Release 15.0(1)SY.

15.1(1)SG

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

Cisco IOS XE Release 3.3SG

This command was modified. Support for 4-byte autonomous system numbers in asplain and asdot notation was added.

Usage Guidelines

Use this command to set the SoO value for a BGP neighbor. The SoO value is set under address family IPv4 VRF configuration mode either directly for a neighbor or for a BGP peer group.

The SoO extended community is a BGP extended community attribute that is used to identify routes that have originated from a site so that the readvertisement of that prefix back to the source site can be prevented. The SoO extended community uniquely identifies the site from which a router has learned a route. BGP can use the SoO value associated with a route to prevent routing loops.

In releases prior to Cisco IOS Release 12.4(11)T, 12.2(33)SRB, and 12.2(33)SB, the SoO extended community attribute is configured using an inbound route map that sets the SoO value during the update process. The introduction of the neighbor soo and soo commands simplifies the SoO value configuration.


Note


A BGP neighbor or peer policy template-based SoO configuration takes precedence over an SoO value configured in an inbound route map.


In Cisco IOS Release 12.4(24)T, the Cisco implementation of 4-byte autonomous system numbers uses asdot--1.2 for example--as the only configuration format, regular expression match, and output display, with no asplain support.

In Cisco IOS XE Release 2.4, and later releases, the Cisco implementation of 4-byte autonomous system numbers uses asplain--65538 for example--as the default regular expression match and output display format for autonomous system numbers, but you can configure 4-byte autonomous system numbers in both the asplain format and the asdot format as described in RFC 5396. To change the default regular expression match and output display of 4-byte autonomous system numbers to asdot format, use the bgp asnotation dot command followed by the clear ip bgp * command to perform a hard reset of all current BGP sessions.

Examples

The following example shows how to configure an SoO value for a BGP neighbor. Under address family IPv4 VRF, a neighbor is identified and an SoO value is configured for the neighbor.

router bgp 45000
 address-family ipv4 vrf VRF_SOO
  neighbor 192.168.1.2 remote-as 40000
  neighbor 192.168.1.2 activate
  neighbor 192.168.1.2 soo 45000:40
  end

The following example shows how to configure an SoO value for a BGP peer group. Under address family IPv4 VRF, a BGP peer group is configured, an SoO value is configured for the peer group, a neighbor is identified, and the neighbor is configured as a member of the peer group.

router bgp 45000
 address-family ipv4 vrf VRF_SOO
  neighbor SOO_GROUP peer-group
  neighbor SOO_GROUP soo 45000:65
  neighbor 192.168.1.2 remote-as 40000
  neighbor 192.168.1.2 activate
  neighbor 192.168.1.2 peer-group SOO_GROUP 
  end

The following example shows how to configure an SoO value for a BGP neighbor using 4-byte autonomous system numbers. Under address family IPv4 VRF, a neighbor is identified and an SoO value of 1.2:1 is configured for the neighbor. This example requires Cisco IOS Release 12.4(24)T, Cisco IOS XE Release 2.4, or a later release.

router bgp 1.2
 address-family ipv4 vrf site1
  neighbor 192.168.1.2 remote-as 1.14
  neighbor 192.168.1.2 activate
  neighbor 192.168.1.2 soo 1.2:1
  end

Related Commands

Command

Description

address-family ipv4 (BGP)

Enters address family configuration mode to configure a routing session using standard IP Version 4 address prefixes.

router bgp

Configures the BGP routing process.

soo

Sets the SoO value for a BGP peer policy template.

neighbor suppress-signaling-protocol

To suppress a Virtual Private LAN Service (VPLS) signaling protocol use the neighbor suppress-signaling-protocol command in address family configuration or router configuration mode. To remove the entry, use the no form of this command.

neighbor { ipv4-address | ipv6-address | peer-group-name } suppress-signaling-protocol ldp

no neighbor { ipv4-address | ipv6-address | peer-group-name } suppress-signaling-protocol ldp

Syntax Description

ipv4-address

IP address of the neighbor.

ipv6-address

IPv6 address of the neighbor.

peer-group-name

Name of a BGP peer group.

ldp

Specifies that Label Distribution Protocol (LDP) signaling will be suppressed.

Command Default

LDP signaling is not suppressed.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

Cisco IOS XE Release 3.8S

This command was introduced.

   

Usage Guidelines

If you specify that LDP signaling is suppressed by using the ldp keyword, BGP signaling will be enabled.

Examples

Device(config-router-af)# neighbor 10.10.10.1 suppress-signaling-protocol ldp 

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IP Version 4 address prefixes.

address-family ipv6

Places the router in address family configuration mode for configuring routing sessions such as BGP that use standard IPv6 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPN Version 4 address prefixes.

address-family vpnv6

Places the router in address family configuration mode for configuring routing sessions, such as BGP, that use standard VPNv6 address prefixes.

neighbor remote-as

Creates a BGP peer group.

neighbor timers

To set the timers for a specific BGP peer or peer group, use the neighbor timers command in address family or router configuration mode. To clear the timers for a specific BGP peer or peer group, use the no form of this command.

neighbor [ ip-address | p eer-group-name ] timers keepalive holdtime [min-holdtime]

no neighbor [ ip-address | peer-group-name ] timers

Syntax Description

ip-address

(Optional) A BGP peer or peer group IP address.

peer-group-name

(Optional) Name of the BGP peer group.

keepalive

Frequency (in seconds) with which the Cisco IOS software sends keepalive messages to its peer. The default is 60 seconds.The range is from 0 to 65535.

holdtime

Interval (in seconds) after not receiving a keepalive message that the software declares a peer dead. The default is 180 seconds. The range is from 0 to 65535.

min-holdtime

(Optional) Interval (in seconds) specifying the minimum acceptable hold-time from a BGP neighbor. The minimum acceptable hold-time must be less than, or equal to, the interval specified in the holdtimeargument. The range is from 0 to 65535.

Command Default

keepalive : 60 secondsholdtime: 180 seconds

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.0

This command was introduced.

12.0(26)S

The min-holdtime argument was added.

12.3(7)T

The min-holdtime argument was added.

12.2(22)S

The min-holdtime argument was added.

12.2(27)SBC

The min-holdtime argument was added and this command was integrated into Cisco IOS Release 12.2(27)SBC.

12.2(33)SRA

The min-holdtime argument was added and this command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SXH

The min-holdtime argument was added and this command was integrated into Cisco IOS Release 12.2(33)SXH.

Usage Guidelines

The timers configured for a specific neighbor or peer group override the timers configured for all BGP neighbors using the timers bgp command.

When configuring the holdtime argument for a value of less than twenty seconds, the following warning is displayed:

% Warning: A hold time of less than 20 seconds increases the chances of peer flapping

If the minimum acceptable hold-time interval is greater than the specified hold-time, a notification is displayed:

% Minimum acceptable hold time should be less than or equal to the configured hold time 

Note


When the minimum acceptable hold-time is configured on a BGP router, a remote BGP peer session is established only if the remote peer is advertising a hold-time that is equal to, or greater than, the minimum acceptable hold-time interval. If the minimum acceptable hold-time interval is greater than the configured hold-time, the next time the remote session tries to establish, it will fail and the local router will send a notification stating “unacceptable hold time.”


Examples

The following example changes the keepalive timer to 70 seconds and the hold-time timer to 210 seconds for the BGP peer 192.168.47.0:

router bgp 109
 neighbor 192.168.47.0 timers 70 210

The following example changes the keepalive timer to 70 seconds, the hold-time timer to 130 seconds, and the minimum hold-time interval to 100 seconds for the BGP peer 192.168.1.2:

router bgp 45000
 neighbor 192.168.1.2 timers 70 130 100

neighbor translate-update

To enable customer-edge (CE) devices, which are not capable of multicast BGP (mBGP) routing, to participate in a multicast session, use the neighbor translate-update command in address-family configuration mode. To disable mBGP routing on CE devices, use the no form of the command.

neighbor { ipv4-address | ipv6-address } translate-update multicast [unicast]

no neighbor { ipv4-address | ipv6-address } translate-update multicast [unicast]

Syntax Description

ipv4-address

Specifies the multicast IPv4 address for the BGP neighbor.

ipv6-address

Specifies the multicast IPv6 address for the BGP neighbor.

multicast

Specifies multicast address prefixes.

unicast

(Optional) Specifies unicast address prefixes.

Command Default

Command Modes

Address family configuration (config-router-af)

Command History

Release

Modification

12.0(26)S

This command was introduced.

12.3(4)T

This command was integrated into Cisco IOS Release 12.3(4)T.

12.2(25)S

This command was integrated into Cisco IOS Release 12.2(25)S.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.

Cisco IOS XE Release 2.1

This command was introduced on Cisco ASR 1000 Series Routers.

15.4(1)S

This command was modified. Support for translate-update was extended to VRF address-families.

Cisco IOS XE Release 3.11S

This command was modified. Support for translate-update was extended to VRF address-families.

Usage Guidelines

The translate-update keyword in the neighbor command enables CE devices, which cannot send BGP Reverse Path Forwarding (RPF) multicast routes, to advertise its routes to multicast VRF-Lite and multicast VPN (mVPN) for VPNv4 and VPNv6 neighbors. These routes are also advertised through IPv6 over IPv4 tunnel. The translate-update keyword is configured on the provider-edge (PE) devices for multicast routing to neighbor CE devices using the address-family ipv4 vrf or the address-family ipv6 vrf command. The PE devices translate the updates from unicast to multicast on CE devices and put them in the BGP VRF routing table of the PE devices, as multicast updates, for processing. If the optional keyword unicast is also configured, the updates that are not translated to multicast are also placed in the unicast queue of the PE devices and populate the unicast BGP VRF table. The translation from unicast to multicast occurs from CE devices to PE devices only. Prefixes are only advertised from CE devices to the multicast neighbors of the PE devices.

Prior to configuring the translate-update feature, you must enable multicast VRF on the PE devices, along with an active VRF session with the CE devices.

Examples

The following example shows how to configure the translate-update feature for an IPv4 VRF address-family named v1 and BGP neighbor n2:


Note


Peer-template configuration for BGP neighbor is not supported for this feature due to conflicts with the earlier versions of Cisco software.
Device> enable
Device# configure terminal
Device(config)# router bgp 65000
Device(config-router)# address-family ipv4 vrf v1
Device(config-router-af)# neighbor n2 peer-group
Device(config-router-af)# neighbor n2 remote-as 4
Device(config-router-af)# neighbor 10.1.1.1 peer-group n2
Device(config-router-af)# neighbor 10.1.1.1 activate
Device(config-router-af)# neighbor 10.1.1.1 translate-update multicast unicast
Device(config-router-af)# end

The following is sample output from the show bgp vpnv4 multicast vrf command. If the “State/PfxRcd” field displays “NoNeg”, it indicates that the neighbor has a translate-update session:

Device# show bgp vpnv4 multicast vrf v1 summary

BGP router identifier 10.1.3.1, local AS number 65000
BGP table version is 8, main routing table version 8
7 network entries using 1792 bytes of memory
8 path entries using 960 bytes of memory
5/3 BGP path/bestpath attribute entries using 1280 bytes of memory
3 BGP AS-PATH entries using 88 bytes of memory
2 BGP extended community entries using 48 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 4168 total bytes of memory
BGP activity 23/2 prefixes, 33/9 paths, scan interval 60 secs
 
Neighbor        V           AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
10.1.1.1        4            4       5      10        1    0    0 00:01:10 (NoNeg)                         
10.1.3.2        4            2      12      10        8    0    0 00:01:33  

Related Commands

Command

Description

address-family ipv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.

address-family ipv6

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv6 address prefixes.

neighbor peer-group

Creates a BGP or multiprotocol BGP peer group.

neighbor remote-as

Adds an entry to a BGP or multiprotocol BGP neighbor table.

neighbor activate

Enables exchange of information with a BGP neighbor.

show bgp vpnv4 multicast

Displays Virtual Private Network Version 4 (VPNv4) multicast entries in a BGP table.

neighbor transport

To enable a TCP transport session option for a Border Gateway Protocol (BGP) session, use the neighbor transport command in router or address family configuration mode. To disable a TCP transport session option for a BGP session, use the no form of this command.

neighbor { ip-address | peer-group-name } transport { connection-mode { active | passive } | path-mtu-discovery [disable] | multi-session }

no neighbor { ip-address | peer-group-name } transport { connection-mode | path-mtu-discovery | multi-session }

Syntax Description

ip-address

IP address of the BGP neighbor.

peer-group-name

Name of a BGP peer group.

connection-mode

Specifies the type of connection (active or passive).

active

Specifies an active connection.

passive

Specifies a passive connection.

path-mtu-discovery

Enables TCP transport path maximum transmission unit (MTU) discovery. TCP path MTU discovery is enabled by default.

multi-session

Enables a separate TCP transport session for each address family.

disable

Disables TCP path MTU discovery.

Command Default

If this command is not configured, TCP path MTU discovery is enabled by default, but no other TCP transport session options are enabled.

Command Modes

Router configuration (config-router)

Address family configuration (config-router-af)

Command History

Release

Modification

12.4

This command was introduced.

12.2(33)SRA

This command was modified. The path-mtu-discovery keyword was added.

12.2(33)SRB

This command was modified. The multi-session, single-session, and disable keywords were added.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

12.4(20)T

This command was modified. The path-mtu-discovery keyword was added.

Cisco IOS XE Release 2.5

This command was integrated into Cisco IOS XE Release 2.5.

15.1(03)S

This command was modified. The single-session keyword was removed. Support for single-session and multi-session transport was integrated in this command.

Usage Guidelines

This command is used to specify various transport options. An active or passive transport connection can be specified for a BGP session. TCP transport path MTU discovery can be enabled to allow a BGP session to take advantage of larger MTU links. Use the show ip bgp neighbors command to determine whether TCP path MTU discovery is enabled.

In Cisco IOS Release 12.2(33)SRB and later releases, options can be specified for the transport of address family traffic using a single TCP session or to enable a separate TCP session for each address family. Multiple TCP sessions are used to support Multitopology Routing (MTR), and the single session option is available for backwards compatibility for non-MTR configurations and for scalability purposes.

In Cisco IOS Release 12.2(33)SRB and later releases, the ability to disable TCP path MTU discovery, for a single neighbor or for an inheriting peer or peer group, was added. If you use the disable keyword to disable discovery, discovery is also disabled on any peer or peer group that inherits the template in which you disabled discovery.

Examples:

The following example shows how to configure the TCP transport connection to be active for a single internal BGP (iBGP) neighbor:

router bgp 45000
neighbor 172.16.1.2 remote-as 45000
neighbor 172.16.1.2 activate
neighbor 172.16.1.2 transport connection-mode active
end

The following example shows how to configure the TCP transport connection to be passive for a single external BGP (eBGP) neighbor:

router bgp 45000
neighbor 192.168.1.2 remote-as 40000
neighbor 192.168.1.2 activate
neighbor 192.168.1.2 transport connection-mode passive
end

The following example shows how to disable TCP path MTU discovery for a single BGP neighbor:

router bgp 45000
neighbor 172.16.1.2 remote-as 45000
neighbor 172.16.1.2 activate
no neighbor 172.16.1.2 transport path-mtu-discovery
end

The following example shows how to reenable TCP path MTU discovery for a single BGP neighbor, if TCP path MTU discovery is disabled:

router bgp 45000
neighbor 172.16.1.2 remote-as 45000
neighbor 172.16.1.2 activate
neighbor 172.16.1.2 transport path-mtu-discovery
end

The following example shows how to enable a separate TCP session for each address family for an MTR topology configuration:

router bgp 45000
scope global
neighbor 172.16.1.2 remote-as 45000
neighbor 172.16.1.2 transport multi-session
address-family ipv4
topology VIDEO 
bgp tid 100
neighbor 172.16.1.2 activate
end

The following example shows how to disable TCP path MTU discovery and verify that it is disabled:

router bgp 100
bgp log-neighbor-changes
timers bgp 0 0
redistribute static
neighbor 10.4.4.4 remote-as 100
neighbor 10.4.4.4 update-source Loopback 0
!end

Device# show ip bgp neighbors 10.4.4.4 | include path
Used as bestpath:             n/a          0
Used as multipath:            n/a          0
Transport(tcp) path-mtu-discovery is enabled 
Option Flags: nagle, path mtu capable
Device#
Device# configure terminal
Device(config)# router bgp 100
Device(config-router)# neighbors 10.4.4.4 transport path-mtu-discovery disable 
Device(config-router)# end
Device# show ip bgp neighbor 10.4.4.4 | include path
Used as bestpath:             n/a          0
Used as multipath:            n/a          0
Transport(tcp) path-mtu-discovery is disabled 

Related Commands

Command

Description

bgp tid

Configures BGP to accept routes with a specified topology ID.

bgp transport

Enables transport session parameters globally for all BGP neighbor sessions.

scope

Defines the scope for a BGP routing session and enters router scope configuration mode.

show ip bgp neighbors

Displays information about BGP and TCP connections to neighbors.

topology (BGP)

Configures a process to route IP traffic under the specified topology instance.

neighbor ttl-security

To secure a Border Gateway Protocol (BGP) peering session and to configure the maximum number of hops that separate two external BGP (eBGP) peers, use the neighbor ttl-securitycommand in address-family or router configuration mode. To disable this feature, use the no form of this command.

neighbor neighbor-address ttl-security hops hop-count

no neighbor neighbor-address ttl-security hops hop-count

Syntax Description

neighbor-address

IP address of the neighbor.

hops hop-count

Number of hops that separate the eBGP peers. The TTL value is calculated by the router from the configured hop-countargument. The value for the hop-count argument is a number between 1 and 254.

Command Default

No default behavior or values

Command Modes

Address-family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.0(27)S

This command was introduced.

12.3(7)T

This command was integrated into Cisco IOS Release 12.3(7)T.

12.2(25)S

This command was integrated into Cisco IOS Release 12.2(25)S.

12.2(18)SXE

This command was integrated into Cisco IOS Release 12.3(7)T.

12.2(27)SBC

This command was integrated into Cisco IOS Release 12.2(27)SBC.

Usage Guidelines

The neighbor ttl-security command provides a lightweight security mechanism to protect BGP peering sessions from CPU utilization-based attacks. These types of attacks are typically brute force Denial of Service (DoS) attacks that attempt to disable the network by flooding the network with IP packets that contain forged source and destination IP addresses in the packet headers.

This feature leverages designed behavior of IP packets by accepting only IP packets with a TTL count that is equal to or greater than the locally configured value. Accurately forging the TTL count in an IP packet is generally considered to be impossible. Accurately forging a packet to match the TTL count from a trusted peer is not possible without internal access to the source or destination network.

This feature should be configured on each participating router. It secures the BGP session in the incoming direction only and has no effect on outgoing IP packets or the remote router. When this feature is enabled, BGP will establish or maintain a session only if the TTL value in the IP packet header is equal to or greater than the TTL value configured for the peering session. This feature has no effect on the BGP peering session, and the peering session can still expire if keepalive packets are not received. If the TTL value in a received packet is less than the locally configured value, the packet is silently discarded and no Internet Control Message Protocol (ICMP) message is generated. This is designed behavior; a response to a forged packet is not necessary.

To maximize the effectiveness of this feature, the hop-count value should be strictly configured to match the number of hops between the local and external network. However, you should also take path variation into account when configuring this feature for a multihop peering session.

The following restrictions apply to the configuration of this command:

  • This feature is not supported for internal BGP (iBGP) peers or iBGP peer groups.

  • The neighbor ttl-security command cannot be configured for a peer that is already configured with the neighbor ebgp-multihop command. The configuration of these commands is mutually exclusive, and only one of these commands is needed to enable a multihop eBGP peering session. An error message will be displayed in the console if you attempt to configure both commands for the same peering session.

  • The effectiveness of this feature is reduced in large-diameter multihop peerings. In the event of a CPU utilization-based attack against a BGP router that is configured for large-diameter peering, you may still need to shut down the affected peering sessions to handle the attack.

  • This feature is not effective against attacks from a peer that has been compromised inside of your network. This restriction also includes peers that are on the network segment between the source and destination network.

Examples

The following example sets the hop count to 2 for a directly connected neighbor. Because the hop-countargument is set to 2, BGP will accept only IP packets with a TTL count in the header that is equal to or greater than 253. If a packet is received with any other TTL value in the IP packet header, the packet will be silently discarded.

neighbor 10.0.0.1 ttl-security hops 2

Related Commands

Command

Description

neighbor ebgp-multihop

Accepts or initiates BGP connections to external peers residing on networks that are not directly connected.

show ip bgp neighbors

Displays information about the TCP and BGP connections to neighbors.

neighbor unsuppress-map

To selectively advertise routes previously suppressed by the aggregate-address command, use the neighbor unsuppress-map command in address family or router configuration mode. To restore the system to the default condition, use the no form of this command.

neighbor { ip-address | peer-group-name } unsuppress-map route-map-name

no neighbor { ip-address | peer-group-name } unsuppress-map route-map-name

Syntax Description

ip-address

IP address of the BGP-speaking neighbor.

peer-group-name

Name of a BGP peer group.

route-map-name

Name of a route map.

Command Default

No routes are unsuppressed.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

12.0(5)T

This command was introduced.

12.0(5)T

Address family configuration mode was added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

Use of the neighbor unsuppress-map command allows specified suppressed routes to be advertised.

Examples

The following BGP router configuration shows that routes specified by a route map named map1 are suppressed:

access-list 3 deny 172.16.16.6
access-list 3 permit any
route-map map1 permit 10
match ip address 3
!
router bgp 65000 
network 172.16.0.0
neighbor 192.168.1.2 remote-as 40000
aggregate-address 172.0.0.0 255.0.0.0 suppress-map map1
neighbor 192.168.1.2 unsuppress-map map1
neighbor 192.168.1.2 activate

The following example shows the routes specified by internal-map being unsuppressed for neighbor 172.16.16.6:

router bgp 100
address-family ipv4 multicast
 network 172.16.0.0
 neighbor 172.16.16.6 unsuppress-map internal-map

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IPv4 address prefixes.

address-family vpnv4

Places the routing in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPNv4 address prefixes.

aggregate-address

Creates an aggregate entry in a BGP routing table.

neighbor route-map

Applies a route map to inbound or outbound routes.

neighbor update-source

To have the Cisco software allow Border Gateway Protocol (BGP) sessions to use any operational interface for TCP connections, use the neighbor update-source command in router configuration mode. To restore the interface assignment to the closest interface, which is called the best local address, use the no form of this command.

neighbor { ip-address | ipv6-address [ % ] | peer-group-name } update-source interface-type interface-number

neighbor { ip-address | ipv6-address [ % ] | peer-group-name } update-source interface-type interface-number

Syntax Description

ip-address

IPv4 address of the BGP-speaking neighbor.

ipv6-address

IPv6 address of the BGP-speaking neighbor.

%

(Optional) IPv6 link-local address identifier. This keyword needs to be added whenever a link-local IPv6 address is used outside the context of its interface.

peer-group-name

Name of a BGP peer group.

interface-type

Interface type.

interface-number

Interface number.

Command Default

Best local address

Command Modes


Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

12.2(4)T

The ipv6-address argument was added.

12.0(21)ST

This command was integrated into Cisco IOS Release 12.0(21)ST.

12.0(22)S

This command was integrated into Cisco IOS Release 12.0(22)S.

12.2(14)S

This command was integrated into Cisco IOS Release 12.2(14)S.

12.2(28)SB

This command was integrated into Cisco IOS Release 12.2(28)SB.

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SRB

The % keyword was added.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Cisco IOS XE Release 2.1

This command was introduced on Cisco ASR 1000 series routers.

15.1(2)SNG

This command was implemented on the Cisco ASR 901 Series Aggregation Services Routers.

Usage Guidelines

This command can work in conjunction with the loopback interface feature described in the “Interface Configuration Overview” chapter of the Cisco IOS Interface and Hardware Component Configuration Guide.

If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

The neighbor update-source command must be used to enable IPv6 link-local peering for internal or external BGP sessions.

The % keyword is used whenever link-local IPv6 addresses are used outside the context of their interfaces and for these link-local IPv6 addresses you must specify the interface they are on. The syntax becomes <IPv6 local-link address>%<interface name>, for example, FE80::1%Ethernet1/0. Note that the interface type and number must not contain any spaces, and be used in full-length form because name shortening is not supported in this situation. The % keyword and subsequent interface syntax is not used for non-link-local IPv6 addresses.

Examples

The following example sources BGP TCP connections for the specified neighbor with the IP address of the loopback interface rather than the best local address:

router bgp 65000
 network 172.16.0.0
 neighbor 172.16.2.3 remote-as 110
 neighbor 172.16.2.3 update-source Loopback0

The following example sources IPv6 BGP TCP connections for the specified neighbor in autonomous system 65000 with the global IPv6 address of loopback interface 0 and the specified neighbor in autonomous system 65400 with the link-local IPv6 address of Fast Ethernet interface 0/0. Note that the link-local IPv6 address of FE80::2 is on Ethernet interface 1/0.

router bgp 65000
 neighbor 3ffe::3 remote-as 65000 
 neighbor 3ffe::3 update-source Loopback0 
 neighbor fe80::2%Ethernet1/0 remote-as 65400 
 neighbor fe80::2%Ethernet1/0 update-source FastEthernet 0/0 
 address-family ipv6 
  neighbor 3ffe::3 activate 
  neighbor fe80::2%Ethernet1/0 activate 
  exit-address-family 

Related Commands

Command

Description

neighbor activate

Enables the exchange of information with a BGP neighboring router.

neighbor remote-as

Adds an entry to the BGP or multiprotocol BGP neighbor table.

neighbor version

To configure the Cisco IOS software to accept only a particular BGP version, use the neighbor version command in router configuration mode. To use the default version level of a neighbor, use the noform of this command.

neighbor { ip-address | peer-group-name } version number

no neighbor { ip-address | peer-group-name } version number

Syntax Description

ip-address

IP address of the BGP-speaking neighbor.

peer-group-name

Name of a BGP peer group.

number

BGP version number. The version can be set to 2 to force the software to use only Version 2 with the specified neighbor. The default is to use Version 4 and dynamically negotiate down to Version 2 if requested.

Command Default

BGP Version 4

Command Modes


Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

Entering this command disables dynamic version negotiation.


Note


The Cisco implementation of BGP in Cisco IOS Release 12.0(5)T or earlier releases supports BGP Versions 2, 3, and 4, with dynamic negotiation down to Version 2 if a neighbor does not accept BGP Version 4 (the default version). The Cisco implementation of BGP in Cisco IOS Release 12.0(6)T or later releases supports BGP Version 4 only and does not support dynamic negotiation down to Version 2.


If you specify a BGP peer group by using the peer-group-name argument, all the members of the peer group will inherit the characteristic configured with this command.

Examples

The following example locks down to Version 4 of the BGP protocol:

router bgp 109
 neighbor 172.16.27.2 version 4

Related Commands

Command

Description

neighbor remote-as

Creates a BGP peer group.

neighbor weight

To assign a weight to a neighbor connection, use the neighbor weight command in address family or router configuration mode. To remove a weight assignment, use the no form of this command.

neighbor { ip-address | peer-group-name } weight number

no neighbor { ip-address | peer-group-name } weight number

Syntax Description

ip-address

IP address of the neighbor.

peer-group-name

Name of a BGP peer group.

number

Weight to assign. Acceptable values are from 0 to 65535.

Command Default

Routes learned through another BGP peer have a default weight of 0 and routes sourced by the local router have a default weight of 32768.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

12.0(7)T

Address family configuration mode was added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

All routes learned from this neighbor will have the assigned weight initially. The route with the highest weight will be chosen as the preferred route when multiple routes are available to a particular network.

The weights assigned with the set weight route-map command override the weights assigned using the neighbor weight command.


Note


For weight changes to take effect, use of the clear ip bgp peer-group * command may be necessary.


If you specify a BGP peer group by using the peer-group-nameargument, all the members of the peer group will inherit the characteristic configured with this command.

Examples

The following router configuration mode example sets the weight of all routes learned via 172.16.12.1 to 50:

router bgp 109
 neighbor 172.16.12.1 weight 50

The following address family configuration mode example sets the weight of all routes learned via 172.16.12.1 to 50:

router bgp 109
address-family ipv4 multicast
 neighbor 172.16.12.1 weight 50

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IP Version 4 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard Virtual Private Network (VPN) Version 4 address prefixes.

neighbor distribute-list

Distributes BGP neighbor information as specified in an access list.

neighbor filter-list

Sets up a BGP filter.

neighbor remote-as

Creates a BGP peer group.

network (BGP and multiprotocol BGP)

To specify the networks to be advertised by the Border Gateway Protocol (BGP) and multiprotocol BGP routing processes, use the network command in address family or router configuration mode. To remove an entry from the routing table, use the no form of this command.

network { network-number [ mask network-mask ] | nsap-prefix } [ route-map map-tag ]

no network { network-number [ mask network-mask ] | nsap-prefix } [ route-map map-tag ]

Syntax Description

network-number

Network that BGP or multiprotocol BGP will advertise.

mask network-mask

(Optional) Network or subnetwork mask with mask address.

nsap-prefix

Network service access point (NSAP) prefix of the Connectionless Network Service (CLNS) network that BGP or multiprotocol BGP will advertise. This argument is used only under NSAP address family configuration mode.

route-map map-tag

(Optional) Identifier of a configured route map. The route map should be examined to filter the networks to be advertised. If not specified, all networks are advertised. If the keyword is specified, but no route map tags are listed, no networks will be advertised.

Command Default

No networks are specified.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

12.0

The limit of 200 network commands per BGP router was removed.

11.1(20)CC

The nlri unicast, nlri multicast, and nlri unicast multicast keywords were added.

12.0(7)T

The nlri unicast, nlri multicast, and nlri unicast multicast keywords were removed.

Address family configuration mode was added.

12.2(8)T

The nsap-prefix argument was added to address family configuration mode.

12.2(25)SG

This command was integrated into Cisco IOS Release 12.2(25)SG.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2(33)SRB

This command was integrated into Cisco IOS Release 12.2(33)SRB.

12.2(33)SXH

This command was integrated into Cisco IOS Release 12.2(33)SXH.

Cisco IOS XE 2.6

This command was integrated into Cisco IOS XE Release 2.6.

Usage Guidelines

BGP and multiprotocol BGP networks can be learned from connected routes, from dynamic routing, and from static route sources.

The maximum number of network commands you can use is determined by the resources of the router, such as the configured NVRAM or RAM.

Examples

The following example sets up network 10.108.0.0 to be included in the BGP updates:

router bgp 65100
 network 10.108.0.0

The following example sets up network 10.108.0.0 to be included in the multiprotocol BGP updates:

router bgp 64800
address family ipv4 multicast
 network 10.108.0.0

The following example advertises NSAP prefix 49.6001 in the multiprotocol BGP updates:

router bgp 64500
 address-family nsap
  network 49.6001

Related Commands

Command

Description

address-family ipv4 (BGP)

Enters the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IP Version 4 address prefixes.

address-family vpnv4

Enters the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPNv4 address prefixes.

default-information originate (BGP)

Allows the redistribution of network 0.0.0.0 into BGP.

route-map (IP)

Defines the conditions for redistributing routes from one routing protocol into another.

router bgp

Configures the BGP routing process.

network backdoor

To specify a backdoor route to a BGP-learned prefix that provides better information about the network, use the network backdoor command in address family or router configuration mode. To remove an address from the list, use the no form of this command.

network ip-address backdoor

no network ip-address backdoor

Syntax Description

ip-address

IP address of the network to which you want a backdoor route.

Command Default

No network is marked as having a back door.

Command Modes

Address family configuration (config-router-af)

Router configuration (config-router)

Command History

Release

Modification

10.0

This command was introduced.

12.0(7)T

Address family configuration mode was added.

12.2(33)SRA

This command was integrated into Cisco IOS Release 12.2(33)SRA.

12.2SX

This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.

Usage Guidelines

A backdoor network is assigned an administrative distance of 200. The objective is to make Interior Gateway Protocol (IGP) learned routes preferred. A backdoor network is treated as a local network, except that it is not advertised. A network that is marked as a back door is not sourced by the local router, but should be learned from external neighbors. The BGP best path selection algorithm does not change when a network is configured as a back door.

Examples

The following address family configuration example configures network 10.108.0.0 as a local network and network 192.168.7.0 as a backdoor network:

router bgp 109
address-family ipv4 multicast
 network 10.108.0.0
 network 192.168.7.0 backdoor

The following router configuration example configures network 10.108.0.0 as a local network and network 192.168.7.0 as a backdoor network:

router bgp 109
 network 10.108.0.0
 network 192.168.7.0 backdoor

Related Commands

Command

Description

address-family ipv4 (BGP)

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard IP Version 4 address prefixes.

address-family vpnv4

Places the router in address family configuration mode for configuring routing sessions such as BGP, RIP, or static routing sessions that use standard VPN Version 4 address prefixes.

distance bgp

Allows the use of external, internal, and local administrative distances that could be a better route to a node.

network (BGP and multiprotocol BGP)

Specifies networks to be advertised by the BGP and multiprotocol BGP routing processes.

router bgp

Assigns an absolute weight to a BGP network.