Confederations

The confederations extension to BGP, defined in RFC 3065, provides for the configuration of AS confederations. An AS confederation is a collection of routers, belonging to one or more autonomous systems, advertised as a single AS number to BGP speakers that are not members of the confederation.

Each AS confederation has a confederation ID. A router member of the confederation advertises itself to non-confederation peers using the AS confederation ID. A router member of the confederation advertises itself to other confederation peers using its AS number. A confederation ID can be any value from 1 to 65535.

Each router member of a confederation must identify its confederation member peers.

Confederation information in the AS path sent to a neighbor peer is included by default. Inclusion of confederation information in the AS path sent to a neighbor peer can be disabled. It is possible to have AS path segments that do not adhere strictly to the confederation standard. Strict confederation path standards can be enforced. Strict confederation path enforcement is disabled by default.

See BGP Topology for a depiction of a BGP confederation topology.

Use the bgp confederation-id command, in BGP configuration mode, to specify the confederation this router belongs to.

The following example configures the BGP router to be a member of BGP confederation 100:

System(su-config)->router bgp 65151
System(su-config-bgp)->bgp router-id 151.1.1.9
System(su-config-bgp)->bgp confederation-id 100
System(su-config-bgp)->

Use the neighbor confed-member command, in BGP configuration mode, to configure the neighbor as a member of the router‘s confederation.

The following example configures neighbor 200.51.1.1 as a member of this router‘s confederation:

System(su-config)->router bgp 65151
System(su-config-bgp)->bgp router-id 159.1.1.9
System(su-config-bgp)->bgp confederation-id 100
System(su-config-bgp)->neighbor 200.51.1.1 confed-member
System(su-config-bgp)->

Use the neighbor aggregate-confed command, in BGP configuration mode, to enable the inclusion of confederation information in the AS path sent to this router‘s peers.

The following example disables the inclusion of confederation information in the AS paths sent to this router‘s peers:

System(su-config)->router bgp 65151
System(su-config-bgp)->bgp router-id 159.1.1.9
System(su-config-bgp)->no neighbor 200.51.1.1 aggregate-confed
System(su-config-bgp)->

Use the bgp strict-confeds command, in BGP configuration mode, to enable BGP to drop AS-Paths with non-standard confederation segments.

The following example enables the strict-confeds feature on this router:

System(su-config)->router bgp 65151
System(su-config-bgp)->bgp strict-confeds
System(su-config-bgp)->

See Configuring BGP Confederations for a BGP confederation configuration example.