BGP Address Family Neighbor Configuration¶

From within a BGP address family configuration mode, the neighbor <existing-neighbor> command specifies an existing neighbor defined in BGP Neighbor Configuration mode. This command then enters an address-family-specific neighbor mode. Like address families, the prefix for this mode varies based on the family and type of address family it is run within. For example, with IPv4 unicast mode, the prompt is config-bgp-ip4uni-nbr.

tnsr(config-bgp-ip4uni)# neighbor 203.0.113.14
tnsr(config-bgp-ip4uni-nbr)#

The following commands are available in config-bgp-<familytype>-nbr modes:

activate:

Activate this neighbor for use by BGP.

addpath-tx-all-paths:

Advertise all known paths to this peer, instead of only advertising the base path.

addpath-tx-bestpath-per-as:

Advertise only the best known base paths for each AS.

allowas-in [<occurrence>|origin]:

Allows routes to be received from this peer which are from the same AS of this router, but through a different path.

<occurrence>:: Allowed number of AS occurrences, from 1-10.
origin:: Accept the AS of this router in an AS-path if the route originated in the AS of this router.

as-override:

Override ASNs in outbound updates to this peer if the AS path is identical to the remote AS.

attribute-unchanged [as-path|next-hop|med]:

Propagates route attributes to this peer unchanged. This behavior can be optionally restricted to only specific attributes, including the as-path, next-hop, and med attributes.

capability orf prefix-list (send|receive|both):

Advertise outbound route filtering capability to this peer. This behavior can be restricted by direction, send, receive, or both.

default-originate [route-map <route-map>]:

Enables advertisement of a default route to this peer.

route-map <route-map>:: Restricts this behavior based on the specified route map.

distribute-list <access-list-name> (in|out):

Defines an access list which is used by BGP to filter route updates for this peer, in either the in or out direction.

filter-list <aspath-name> (in|out):

Defines a list which is used by BGP to filter route updates by AS path, rather than prefix.

maximum-prefix [(limit|restart|threshold) <value>|warning-only]:

Defines the maximum number of prefixes this router will accept from the peer before tearing down the BGP session.

Note

This action is considered harsh and the best practice is to filter received prefixes by other mechanisms such as a prefix-list rather than to abruptly break contact in this way.

limit <val>:: The maximum number of prefixes to allow from the peer, from 1-4294967295.
restart <val>:: Restarts the connection after limits are exceeded. The restart is performed at the defined interval, in minutes, from 1-65535.
threshold <val>:: Warning message threshold, from 1-100.
warning-only:: Warn the peer when the limit is exceeded, rather than disconnecting.

next-hop-self [force]:

Uses the address of this router as the next-hop in routes announced to this peer if they are learned via eBGP.

force:: When present, also sets the next-hop to the address of this router on reflected routes.

prefix-list <prefix-list-name> (in|out):

Defines a prefix list which is used by BGP to filter route updates for this peer, in either the in or out direction.

remove-private-AS [all] [replace-AS]:

Prevents the BGP daemon from sending routes with private AS numbers to this peer.

all:: When present, this action applies to all ASNs.
replace-AS:: When present, replaces private AS numbers with the AS number of this router.

route-map <name> (in|out):

Defines a route map which is used by BGP to filter route updates for this peer, in either the in or out direction.

route-reflector-client:

Configures this peer as a route reflector client. This allows routes received from peers in the same AS or using iBGP to be reflected to other peers, avoiding the need for a full mesh configuration between all routing peers.

route-server-client:

Configures this peer as a route server client. This enables transparent mode, which retains attributes unmodified, and maintains a local RIB for this peer.

send-community (standard|large|extended):

Sends the community attribute to this peer, limited to the specified type (standard, large, extended).

soft-reconfiguration inbound:

Allows the peer to send requests for soft reconfiguration, to apply changes to routes or new attributes without the need for a session reset.

unsuppress-map <route-map>:

Configures a route map which BGP can use to unsuppress routes that would otherwise be suppressed by other configuration settings.

weight <weight>:

Applies the given weight to routes received from this peer.