Table Of Contents

neighbor timers

neighbor transport

neighbor ttl-security

neighbor unsuppress-map

neighbor update-source

neighbor version

neighbor weight

network (BGP and multiprotocol BGP)

network backdoor

redistribute (BGP to ISO IS-IS)

redistribute (ISO IS-IS to BGP)

redistribute dvmrp

router bgp

scope

set as-path

set comm-list delete

set community

set dampening

set extcommunity

set extcommunity cost

set ip next-hop (BGP)

set metric (BGP-OSPF-RIP)

set metric-type internal

set origin (BGP)

set traffic-index

set weight

show bgp nsap

show bgp nsap community

show bgp nsap community-list

show bgp nsap dampening

show bgp nsap dampened-paths

show bgp nsap filter-list

show bgp nsap flap-statistics

show bgp nsap inconsistent-as

show bgp nsap neighbors

show bgp nsap paths

show bgp nsap quote-regexp

show bgp nsap regexp

show bgp nsap summary

neighbor timers

To set the timers for a specific BGP peer or peer group, use the neighbor timers command in 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 | peer-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 holdtime argument. The range is from 0 to 65535.

Defaults

keepalive: 60 seconds
holdtime: 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 hold-time argument was added.
12.3(7)T	The min hold-time 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 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 | multi-session | single-session}

no neighbor {ip-address | peer-group-name} transport {connection-mode | path-mtu-discovery | multi-session | single-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	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.
single-session	Enables all address families to use a single TCP transport session.

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	The path-mtu-discovery keyword was added.
12.2(33)SRB	The multi-session and single-session 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	The path-mtu-discovery keyword was added.

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 Multi-Topology Routing (MTR), and the single session option is available for backwards compatibility for non-MTR configurations and for scalability purposes.

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

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-security command 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-count argument. The value for the hop-count argument is a number between 1 and 254.

Defaults

No default behavior or values

Command Modes

Address-family configuration
Router configuration

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-count argument 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
Router configuration

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 internal-map 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 IOS 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

no 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.

Defaults

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.

Usage Guidelines

This command can work in conjunction with the loopback interface feature described in the "Interface Configuration Overview" chapter of the Release 12.3 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. This keyword does not need to be 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:

router bgp 65000

  neighbor 3ffe::3 remote-as 65000 

  neighbor 3ffe::3 update-source Loopback0 

  neighbor fe80::2 remote-as 65400 

  neighbor fe80::2 update-source FastEthernet 0/0 

  address-family ipv6 

   neighbor 3ffe::3 activate 

   neighbor fe80::2 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 no form 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.

Defaults

BGP Version 4

Command Modes

Router configuration

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.

Defaults

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
Router configuration

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-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 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
Router configuration

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

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.

Defaults

No network is marked as having a back door.

Command Modes

Address family configuration
Router configuration

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.

redistribute (BGP to ISO IS-IS)

To redistribute routes from a Border Gateway Protocol (BGP) autonomous system into an International Organization for Standardization (ISO) Intermediate System-to-Intermediate System (IS-IS) routing process, use the redistribute command in router configuration mode. To remove the redistribute command from the configuration file and restore the system to its default condition where the software does not redistribute routes, use the no form of this command.

redistribute protocol as-number [route-type] [route-map map-tag]

no redistribute protocol as-number [route-type] [route-map map-tag]

Syntax Description

protocol	Source protocol from which routes are being redistributed. It must be the bgp keyword. The bgp keyword is used to redistribute dynamic routes.
as-number	The autonomous system number of the BGP routing process.
route-type	(Optional) The type of route to be redistributed. It can be one of the following keywords: clns or ip. The default is ip. The clns keyword is used to redistribute BGP routes with network service access point (NSAP) addresses into IS-IS. The ip keyword is used to redistribute BGP routes with IP addresses into IS-IS.
route-map map-tag	(Optional) Identifier of a configured route map. The route map should be examined to filter the importation of routes from this source routing protocol to IS-IS. If not specified, all routes are redistributed. If the keyword is specified, but no route map tags are listed, no routes will be imported.

Command Default

Route redistribution is disabled.

protocol: No source protocol is defined.
route-type: ip
route-map map-tag: If the route-map argument is not entered, all routes are redistributed; if no
     map-tag value is entered, no routes are imported.

Command Modes

Router configuration

Command History

Release	Modification
12.2(8)T	The clns keyword was added.
12.2(33)SRB	This command was integrated into Cisco IOS Release 12.2(33)SRB.

Usage Guidelines

The clns keyword must be specified to redistribute NSAP prefix routes from BGP into an ISO IS-IS routing process. This version of the redistribute command is used only under router configuration mode for IS-IS processes.

Examples

The following example configures NSAP prefix routes from BGP autonomous system 64500 to be redistributed into the IS-IS routing process called osi-proc-17:

router isis osi-proc-17

 redistribute bgp 64500 clns

Related Commands

Command	Description
network (BGP and multiprotocol BGP)	Specifies the list of networks for the BGP routing process.
route-map (IP)	Defines the conditions for redistributing routes from one routing protocol into another.
show route-map	Displays all route maps configured or only the one specified.

redistribute (ISO IS-IS to BGP)

To redistribute routes from an International Organization for Standardization (ISO) Intermediate System-to-Intermediate System (IS-IS) routing process into a Border Gateway Protocol (BGP) autonomous system, use the redistribute command in address family or router configuration mode. To remove the redistribute command from the configuration file and restore the system to its default condition where the software does not redistribute routes, use the no form of this command.

redistribute protocol [process-id] [route-type] [route-map [map-tag]]

no redistribute protocol [process-id] [route-type] [route-map [map-tag]]

Syntax Description

protocol	Source protocol from which routes are being redistributed. It can be one of the following keywords: isis or static. The isis keyword is used to redistribute dynamic routes. The static keyword is used to redistribute static routes.
process-id	(Optional) When IS-IS is used as a source protocol, this argument defines a meaningful name for a routing process. The process-id argument identifies from which IS-IS routing process routes will be redistributed. Routes can be redistributed only from IS-IS routing processes that involve Level 2 routes, including IS-IS Level 1-2 and Level 2 routing processes. The process-id argument is not used when the protocol keyword is static.
route-type	(Optional) The type of route to be redistributed. It can be one of the following keywords: clns or ip. The default is ip. The clns keyword is used to redistribute Connectionless Network Service (CLNS) routes with network service access point (NSAP) addresses into BGP. The ip keyword is used to redistribute IS-IS routes with IP addresses into BGP.
route-map map-tag	(Optional) Identifier of a configured route map. The route map should be examined to filter the importation of routes from this source routing protocol to BGP. If no route map is specified, all routes are redistributed. If the route-map keyword is specified, but no map-tag value is entered, no routes will be imported.

Command Default

Route redistribution is disabled.

route-type: ip
route-map map-tag: If the route-map argument is not entered, all routes are redistributed; if no
     map-tag value is entered, no routes are imported.

Command Modes

Address family configuration (Cisco IOS 12.3(8)T and later releases)
Router configuration (T-releases after Cisco IOS 12.3(8)T)

Command History

Release	Modification
12.2(8)T	The clns keyword was added.
12.3(8)T	Beginning with Cisco IOS Release 12.3(8)T this version of the redistribute command should be entered under address family mode rather than router configuration mode.
12.2(33)SRB	This command was integrated into Cisco IOS Release 12.2(33)SRB.

Usage Guidelines

The clns keyword must be specified to redistribute NSAP prefix routes from an ISO IS-IS routing process into BGP. Beginning with Cisco IOS Release 12.3(8)T, this version of the redistribute command is entered only in address family configuration mode for BGP processes.

Examples

Cisco IOS Releases Prior to Release 12.3(8)T

The following example configures CLNS NSAP routes from the IS-IS routing process called osi-proc-6 to be redistributed into BGP:

Router(config)# router bgp 64352

Router(config-router)# redistribute isis osi-proc-6 clns

Cisco IOS Releases 12.3(8)T and Later Releases

The following example configures CLNS NSAP routes from the IS-IS routing process called osi-proc-15 to be redistributed into BGP:

Router(config)# router bgp 404

Router(config-router)# address-family nsap

Router(config-router-af)# redistribute isis osi-proc-15 clns

Related Commands

Command	Description
network (BGP and multiprotocol BGP)	Specifies the list of networks for the BGP routing process.
route-map (IP)	Defines the conditions for redistributing routes from one routing protocol into another.
show route-map	Displays all route maps configured or only the one specified.

redistribute dvmrp

To configure redistribution of Distance Vector Multicast Routing Protocol (DVMRP) routes into multiprotocol BGP, use the redistribute dvmrp command in address family or router configuration mode. To stop such redistribution, use the no form of this command.

redistribute dvmrp [route-map map-name]

no redistribute dvmrp [route-map map-name]

Syntax Description

route-map map-name

(Optional) Name of the route map that contains various BGP attribute settings.

Defaults

DVMRP routes are not redistributed into multiprotocol BGP.

Command Modes

Address family configuration
Router configuration

Command History

Release	Modification
11.1(20)CC	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

Use this command if you have a subset of DVMRP routes in an autonomous system that you want to take the multiprotocol BGP path. Define a route map to further specify which DVMRP routes get redistributed.

Examples

The following router configuration mode example redistributes DVMRP routes to BGP peers that match access list 1:

router bgp 109

 redistribute dvmrp route-map dvmrp-into-mbgp

route-map dvmrp-into-mbgp

 match ip address 1

The following address family configuration mode example redistributes DVMRP routes to multiprotocol BGP peers that match access list 1:

router bgp 109

address-family ipv4 multicast

 redistribute dvmrp route-map dvmrp-into-mbgp

route-map dvmrp-into-mbgp

 match ip address 1

router bgp

To configure the BGP routing process, use the router bgp command in global configuration mode. To remove a routing process, use the no form of this command.

router bgp autonomous-system-number

no router bgp autonomous-system-number

Syntax Description

autonomous-system-number

Number of an autonomous system that identifies the router to other BGP routers and tags the routing information passed along.

Defaults

No BGP routing process is enabled by default.

Command Modes

Global configuration (config)

Command History

Release	Modification
10.0	This command was introduced.
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(31)SB2	This command was integrated into Cisco IOS Release 12.2(31)SB2.
12.2(33)SRB	Support for IPv6 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.
12.2(33)SB	Support for IPv6 was added.

Usage Guidelines

This command allows you to set up a distributed routing core that automatically guarantees the loop-free exchange of routing information between autonomous systems.

Examples

The following example configures a BGP process for autonomous system 55000:

router bgp 55000

Related Commands

Command	Description
network (BGP and multiprotocol BGP)	Specifies the list of networks for the BGP routing process.
timers bgp	Adjusts BGP network timers.

scope

To define the scope for a Border Gateway Protocol (BGP) routing session and to enter r