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Cisco IOS IP Command Reference, Volume 2 of 4: Routing Protocols, Release 12.3
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Introduction
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IP Routing Protocol Commands: A through B
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IP Routing Protocols Commands: C through H
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IP Routing Protocols Commands: I
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IP Routing Protocols Commands: K through M
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IP Routing Protocols Commands: N
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IP Routing Protocols Commands: O through R
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IP Routing Protocols Commands: send-lifetime through set-overload-bit
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IP Routing Protocols Commands: show bgp nsap through show ip local policy
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IP Routing Protocols Commands: show ip ospf through version
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Table Of Contents
neighbor advertisement-interval
neighbor database-filter all out
neighbor disable-connected-check
neighbor peer-group (assigning members)
neighbor peer-group (creating)
neighbor route-reflector-client
network (BGP and multiprotocol BGP)
neighbor (EIGRP)
To define a neighboring router with which to exchange routing information on a router that is running Enhanced Interior Gateway Routing Protocol (EIGRP), use the neighbor command in router configuration mode. To remove an entry, use the no form of this command.
neighbor ip-address interface-type interface-number
no neighbor ip-address interface-type interface-number
Syntax Description
Command Default
No neighboring routers are defined.
Command Modes
Router configuration
Command History
Usage Guidelines
Multiple neighbor statements can be used to establish peering sessions with specific EIGRP neighbors. The interface through which EIGRP will exchange routing updates must be specified in the neighbor statement. The interfaces through which two EIGRP neighbors exchange routing updates must be configured with IP addresses from the same network.
Note
Configuring the passive-interface command suppresses all incoming and outgoing routing updates and hello messages. EIGRP neighbor adjacencies cannot be established or maintained over an interface that is configured as passive.
Examples
The following example configures EIGRP peering sessions with the 192.168.1.1 and 192.168.2.2 neighbors:
router eigrp 1network 192.168.0.0neighbor 192.168.1.1 Ethernet 0/0neighbor 192.168.2.2 Ethernet 1/1Related Commands
neighbor (OSPF)
To configure OSPF routers interconnecting to nonbroadcast networks, use the neighbor command in router configuration mode. To remove a configuration, use the no form of this command.
neighbor ip-address [priority number] [poll-interval seconds] [cost number] [database-filter all]
no neighbor ip-address [priority number] [poll-interval seconds] [cost number] [database-filter all]
Syntax Description
Defaults
No configuration is specified.
Command Modes
Router configuration
Command History
Usage Guidelines
X.25 and Frame Relay provide an optional broadcast capability that can be configured in the map to allow OSPF to run as a broadcast network. At the OSPF level you can configure the router as a broadcast network. Refer to the x25 map and frame-relay map commands in the "X.25 Commands" and "Frame Relay Commands" chapters, respectively, in the Cisco IOS Wide-Area Networking Command Reference for more detail.
One neighbor entry must be included in the Cisco IOS software configuration for each known nonbroadcast network neighbor. The neighbor address must be on the primary address of the interface.
If a neighboring router has become inactive (hello packets have not been received for the Router Dead Interval period), it may still be necessary to send hello packets to the dead neighbor. These hello packets will be sent at a reduced rate called Poll Interval.
When the router first starts up, it sends only hello packets to those routers with nonzero priority, that is, routers that are eligible to become designated routers (DRs) and backup designated routers (BDRs). After the DR and BDR are selected, DR and BDR will then start sending hello packets to all neighbors in order to form adjacencies.
Note
Prior to Cisco IOS Release 12.0, the neighbor command applied to NBMA networks only. With Release 12.0, the neighbor command applies to NBMA networks and point-to-multipoint networks. On NBMA networks, the cost keyword is not accepted.
Examples
The following example declares a router at address 192.168.3.4 on a nonbroadcast network, with a priority of 1 and a poll interval of 180 seconds:
router ospf 1neighbor 192.168.3.4 priority 1 poll-interval 180The following example illustrates a point-to-multipoint network with nonbroadcast:
interface Serial0ip address 10.0.1.1 255.255.255.0ip ospf network point-to-multipoint non-broadcastencapsulation frame-relayno keepaliveframe-relay local-dlci 200frame-relay map ip 10.0.1.3 202frame-relay map ip 10.0.1.4 203frame-relay map ip 10.0.1.5 204no shut!router ospf 1network 10.0.1.0 0.0.0.255 area 0neighbor 10.0.1.3 cost 5neighbor 10.0.1.4 cost 10neighbor 10.0.1.5 cost 15Related Commands
ip ospf priority
Sets the router priority, which helps determine the designated router for this network.
neighbor (RIP)
To define a neighboring router with which to exchange routing information, use the neighbor command in router configuration mode. To remove an entry, use the no form of this command.
neighbor ip-address
no neighbor ip-address
Syntax Description
Defaults
No neighboring routers are defined.
Command Modes
Router configuration
Command History
Usage Guidelines
This command permits the point-to-point (nonbroadcast) exchange of routing information. When it is used in combination with the passive-interface router configuration command, routing information can be exchanged between a subset of routers and access servers on a LAN.
Multiple neighbor commands can be used to specify additional neighbors or peers.
Examples
In the following example, RIP updates are sent to all interfaces on network 10.108.0.0 except Ethernet interface 1. However, in this case a neighbor router configuration command is included. This command permits the sending of routing updates to specific neighbors. One copy of the routing update is generated per neighbor.
router ripnetwork 10.108.0.0passive-interface ethernet 1neighbor 10.108.20.4Related Commands
neighbor advertise-map
To install a Border Gateway Protocol (BGP) route as a locally originated route in the BGP routing table for conditional advertisement, use the neighbor advertise-map command in router configuration mode. To disable conditional advertisement, use the no form of this command.
neighbor ip-address advertise-map map-name {exist-map map-name | non-exist-map map-name}
no neighbor ip-address advertise-map map-name {exist-map map-name | non-exist-map map-name}
Syntax Description
Defaults
No default behavior or values
Command Modes
Address family
Router configurationCommand History
11.1CC
This command was introduced.
11.2
This command was integrated into Cisco IOS Release 11.2.
Usage Guidelines
Use the neighbor advertise-map router configuration command to conditionally advertise selected routes. The routes or prefixes that will be conditionally advertised are defined in 2 route-maps, an advertise map and an exist map or nonexist map. The route map associated with the exist map or nonexist 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. When configuring an exist map, the condition is met when the prefix exists in both the advertise map and the exist map. When configuring a nonexist map, the condition is met when the prefix exists in the advertise map but does not exist in the nonexist 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 conditionally advertise a prefix to the 10.2.1.1 neighbor using an exist map. If the prefix exists in MAP1 and MAP2, the condition is met and the prefix is advertised.
router bgp 50000neighbor 10.2.1.1 advertise-map MAP1 exist-map MAP2The following address family configuration example configures BGP to conditionally advertise a prefix to the 10.1.1.1 neighbor using a nonexist map. If the prefix exists in MAP3 but not MAP4, the condition is met and the prefix is advertised.
router bgp 50000address-family ipv4 multicastneighbor 10.1.1.1 advertise-map MAP3 non-exist-map MAP4Related Commands
neighbor advertisement-interval
To set the minimum interval between the sending of BGP routing updates, use the neighbor advertisement-interval 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} advertisement-interval seconds
no neighbor {ip-address | peer-group-name} advertisement-interval seconds
Syntax Description
ip-address
IP address of the number.
peer-group-name
Name of a BGP peer group.
seconds
Time (in seconds) is specified by an integer ranging from 0 to 600.
Defaults
30 seconds for external peers and 5 seconds for internal peers.
Command Modes
Address family configuration
Router configuration
Command History
10.3
This command was introduced.
12.0(7)T
Address family configuration mode was added.
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
The following router configuration mode example sets the minimum time between sending BGP routing updates to 10 seconds:
router bgp 50000neighbor 10.4.4.4 advertisement-interval 10The following address family configuration mode example sets the minimum time between sending BGP routing updates to 10 seconds:
router bgp 50000address-family ipv4 unicastneighbor 10.4.4.4 advertisement-interval 10Related Commands
neighbor database-filter all out
To filter outgoing link-state advertisements (LSAs) to an Open Shortest Path First (OSPF) neighbor, use the neighbor database-filter all out command in router configuration mode. To restore the forwarding of LSAs to the neighbor, use the no form of this command.
neighbor ip-address database-filter all out [cost metric]
no neighbor ip-address database-filter all out
Syntax Description
ip-address
IP address of the neighbor to which outgoing LSAs are blocked.
cost metric
(Optional) Cost metric configured for the specified neighbor. The range of this value is from 0 to 65535.
Defaults
This command is disabled by default. All outgoing LSAs are flooded to the neighbor.
Command Modes
Router configuration
Command History
12.0
This command was introduced.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
Usage Guidelines
This command performs the same function that the ip ospf database-filter all outcommand performs on an interface basis.
Examples
The following example prevents flooding of OSPF LSAs to point-to-multipoint networks to the neighbor at IP address 10.2.3.4:
router ospf 109neighbor 10.2.3.4 database-filter all outRelated Commands
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.
Defaults
No default route is sent to the neighbor.
Command Modes
Address family configuration
Router configuration
Command History
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.
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 50000network 172.16.0.0neighbor 172.16.2.3 remote-as 6000neighbor 172.16.2.3 default-originateIn the following address family configuration example, the local router injects route 0.0.0.0 to the neighbor 172.16.2.3 unconditionally:
router bgp 50000neighbor 172.16.2.3 remote-as 6000address-family ipv4 unicastnetwork 172.16.0.0neighbor 172.16.2.3 default-originateIn 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 192.168.0.0 (that is, if a route with any mask exists, such as 255.255.255.0 or 255.255.0.0):
router bgp 50000network 172.16.0.0neighbor 172.16.2.3 remote-as 60000neighbor 172.16.2.3 default-originate route-map default-map!route-map default-map 10 permitmatch ip address 1!access-list 1 permit 192.168.0.0In 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 192.168.0.0 with a mask of 255.255.0.0:
router bgp 50000network 172.16.0.0neighbor 172.16.2.3 remote-as 60000neighbor 172.16.2.3 default-originate route-map default-map!route-map default-map 10 permitmatch ip address 1!access-list 100 permit ip host 192.168.0.0 host 255.255.255.0Related Commands
neighbor description
To associate a description with a neighbor, use the neighbor description command in router 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 a BGP peer group.
text
Text (up to 80 characters) that describes the neighbor.
Defaults
There is no description of the neighbor.
Command Modes
Router configuration
Command History
Examples
In the following example, the description of the neighbor is "peer with xyz.com":
router bgp 50000network 172.16.0.0neighbor 172.16.2.3 description peer with xyz.comneighbor 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
Defaults
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
Router ConfigurationCommand History
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:
BGP Peer 1
Router(config)# interface loopback 1Router(config-if)# ip address 10.0.0.100 255.255.255Router(config-if)# exitRouter(config)# router bgp 64512Router(config-router)# neighbor 192.168.0.200 remote-as 65534Router(config-router)# neighbor 192.168.0.200 ebgp-multihop 1Router(config-router)# neighbor 192.168.0.200 update-source loopback 2Router(config-router)# neighbor 192.168.0.200 disable-connected-checkRouter(config-router)# endBGP Peer 2
Router(config)# interface loopback 2Router(config-if)# ip address 192.168.0.200 255.255.255Router(config-if)# exitRouter(config)# router bgp 65534Router(config-router)# neighbor 10.0.0.100 remote-as 64512Router(config-router)# neighbor 10.0.0.100 ebgp-multihop 1Router(config-router)# neighbor 10.0.0.100 update-source loopback 1Router(config-router)# neighbor 10.0.0.100 disable-connected-checkRouter(config-router)# endRelated Commands
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
Defaults
No BGP neighbor is specified.
Command Modes
Address family configuration
Router configuration
Command History
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:
•
•
•
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
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 10.108.0.0.
router bgp 50000network 10.108.0.0neighbor 172.16.4.1 distribute-list 39 inThe 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 50000network 10.108.0.0neighbor 172.16.4.1 distribute-list 101 inExample A
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 0.0.0.0access-list 101 deny ip 192.168.0.0 0.0.255.255 255.255.0.0 0.0.255.255Example B
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 0.0.0.0access-list 101 deny ip 10.108.0.0 0.0.255.255 255.255.0.0 0.0.255.255Example C
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 0.0.0.255access-list 101 permit ip 0.0.0.0 255.255.255.255 0.0.0.0 255.255.255.255Related Commands
neighbor dmzlink-bw
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 BGP Link Bandwidth feature, use the no form of this command.
neighbor {ip-address} dmzlink-bw
no neighbor {ip-address} dmzlink-bw
Syntax Description
ip-address
The address of the neighbor router for which the bandwidth of the outbound link is advertised.
Defaults
This command is disabled by default.
Command Modes
Address family configuration
Command History
Usage Guidelines
Use the neighbor dmzlink-bw command to advertise the bandwidth of links that are used to exit an autonomous system. This feature only supports single hop links over internal Border Gateway Protocol (iBGP). BGP can originate the link bandwidth community only for external BGP (eBGP) peers that are one hop away.
Examples
The following example advertises the bandwidth of the link to router 10.1.1.1:
neighbor 10.1.1.1 dmzlink-bwRelated Commands
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 | peer-group-name} ebgp-multihop [ttl]
no neighbor {ip-address | peer-group-name} ebgp-multihop
Syntax Description
ip-address
IP 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.
Defaults
Only directly connected neighbors are allowed.
Command Modes
Router configuration
Command History
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 50000neighbor 10.108.1.1 ebgp-multihopRelated Commands
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
Defaults
No filter is used.
Command Modes
Address family configuration
Router configuration
Command History
10.0
This command was introduced.
12.0(7)T
Address family configuration mode was added.
12.1
The weight keyword was removed.
Usage Guidelines
This command establishes filters on both inbound and outbound BGP routes.
The weights assigned with the match as-path and set weight route-map configuration commands override the weights assigned using the neighbor weight command.
Refer to the "Regular Expressions" appendix in the Cisco IOS Terminal Services Configuration Guide for information on forming regular expressions.
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.
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$router bgp 50000network 10.108.0.0neighbor 192.168.6.6 remote-as 6000neighbor 172.16.1.1 remote-as 47neighbor 172.16.1.1 filter-list 1 outIn the following address family configuration mode example, the BGP neighbor with IP address 172.16.1.1 is not sent advertisements about any path through or from the adjacent autonomous system 60000:
ip as-path access-list 1 deny _60000_ip as-path access-list 1 deny ^60000$router bgp 50000address-family ipv4 unicastnetwork 10.108.0.0neighbor 192.168.6.6 remote-as 60000neighbor 172.16.1.1 remote-as 47neighbor 172.16.1.1 filter-list 1 outRelated Commands
neighbor local-as
To allow customization of the autonomous system number for external Border Gateway Protocol (eBGP) peer groupings, use the neighbor local-as 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} local-as as-number [no-prepend]
no neighbor {ip-address | peer-group-name} local-as as-number
Syntax Description
Defaults
The local autonomous system number is prepended to all external routes unless the no-prepend keyword is used.
Command Modes
Address family configuration
Router configuration
Command History
12.0(4.4)S
This command was introduced.
12.0(5)T
Address family configuration mode was added.
12.2(8)T
The no-prepend keyword was added.
Usage Guidelines
Each BGP peer or peer group can be made to have a local autonomous system value for the purpose of peering. In the case of peer groups, the local autonomous system value is valid for all peers in the peer group. This feature cannot be customized for individual peers in a peer group.
If this command is configured, you cannot use the local BGP autonomous system number or the autonomous system number of the remote peer.
This command is valid only if the peer is a true eBGP peer. This feature does not work for two peers in different subautonomous systems in a confederation.
The no-prepend keyword should be used only to change the autonomous system number in a BGP network and should be deconfigured after the transition is complete because routing loops can be created if this feature is used incorrectly.
Examples
The following address family configuration example shows the customization of neighbor 172.16.1.1 configured to have an autonomous system number of 300 for the purpose of peering:
router bgp 50000address-family ipv4 multicastnetwork 172.16.0.0neighbor 172.16.1.1 local-as 300The following router configuration example shows the customization of neighbor 172.16.1.1 configured to have autonomous system number of 300 for the purpose of peering:
router bgp 5000network 172.16.0.0neighbor 172.16.1.1 local-as 300
