Deployment Guide

Configuring BGP Confederations
Another way to organize routers within an AS and reduce the mesh for IBGP peers is to configure BGP confederations.
As with route reflectors, BGP confederations are recommended only for IBGP peering involving many IBGP peering sessions
per router. Basically, when you configure BGP confederations, you break the AS into smaller sub-AS, and to those outside your
network, the confederations appear as one AS. Within the confederation sub-AS, the IBGP neighbors are fully meshed and the
MED, NEXT_HOP, and LOCAL_PREF attributes are maintained between confederations.
To configure BGP confederations, use the following commands.
● Specifies the confederation ID.
CONFIG-ROUTER-BGP mode
bgp confederation identifier as-number
○ as-number: from 0 to 65535 (2 Byte) or from 1 to 4294967295 (4 Byte).
● Specifies which confederation sub-AS are peers.
CONFIG-ROUTER-BGP mode
bgp confederation peers as-number [... as-number]
○ as-number: from 0 to 65535 (2 Byte) or from 1 to 4294967295 (4 Byte).
All Confederation routers must be either 4 Byte or 2 Byte. You cannot have a mix of router ASN support.
To view the configuration, use the show config command in CONFIGURATION ROUTER BGP mode.
Configuring a BGP VRF address family
To perform BGP configuration between two neighbors that must exchange IPv6 or IPv4 VRF information, use the following
commands.
Following are the steps to configure BGP VRF address-family between two peers.
● Configure a VRF routing table.
CONFIG mode
ip vrf vrf-name
For more information on VRF configuration, see Virtual Routing and Forwarding (VRF).
● Enter the router configuration mode and the AS number.
CONFIG mode
router bgp as-number
● Specify the IPv4 address family configuration.
CONFIG-ROUTER-BGP mode
address-family {ipv4 [multicast] | ipv6 unicast} vrf vrf-name
vrf vrf-name — Specifies the name of VRF instance associated with the IPv4 or IPv6 address-family configuration.
● Add the IP address of the neighbor in the specified AS to the IPv4 MBGP neighbor table.
CONFIG-ROUTER-BGP-AF mode
neighbor {ip-address | ipv6–address | peer-group-name} remote-as as-number
● Enable the neighbor.
CONFIG-ROUTER-BGP mode
neighbor ip-address no shutdown
● Specify the number of prefixes that can be received from a neighbor.
CONFIG-ROUTER-BGP-AF mode
neighbor {ip-address | ipv6–address | peer-group-name} maximum—prefix maximum [threshold]
[warning-only]as-number
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Border Gateway Protocol (BGP)