Configuring BGP Confederations Sample Configuration

Note The example shows only a portion of the configuration of router 1.0.0.4. The configuration displayed is not a complete configuration—only those parts that are relevant to BGP confederations are displayed.

Note The example shows only a portion of the configuration of router 1.0.0.4. The configuration displayed is not a complete configuration—only those parts that are relevant to BGP confederations are displayed.

AS 123 is transformed into a BGP confederation. The member-AS 65001 serves as a central member-AS. Member autonomous systems 65002 and 65003 are connected to AS 65001. From the outside, the confederation looks like a single AS, still identified by AS number 123.

The internal member-AS number is specified in the router bgp configuration command. This number is the AS number that will be prepended to the AS-path attribute by the router when updates are forwarded across intra-confederation EBGP sessions.

The original, official AS number is given as the BGP confederation identifier. This number is the AS number that will replace the internal member-AS information when egress confederation routers forward updates across EBGP sessions with external autonomous systems.

The bgp confederation peers configuration step allows the router to identify the type of session to be opened with the BGP peers that are configured through the neighbor statement.

Neighbor 1.0.0.3 is in the same member-AS, so its session is an IBGP session. Both neighbor 1.0.0.2 (AS 65002) and 1.0.0.1 (AS 65003) belong to different member autonomous systems (the AS number appears in the list of BGP confederation peers), so their sessions are intra-confederation EBGP sessions.

Neighbor 2.7.1.1 belongs to AS 222, which is not listed as a member-AS in the bgp confederation peers command, so its session is a true EBGP session.

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Configuring BGP on Cisco Routers (BGP) v3.2

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