Configuring a BGP Confederation

BGP confederations can be configured on a large BGP network to reduce the number of IBGP connections and simplify routing policy management, increasing route advertisement efficiency.

Context

A confederations can be used to reduce the number of IBGP connections in an AS. It divides an AS into several sub-ASs. Full-mesh IBGP connections are established between devices in each sub-AS, and full-mesh EBGP connections are established between devices in different sub-ASs.

Compared with RRs, confederations facilitate IGP extensions.

Procedure

Configure a BGP confederation.
1. Access the system view.
  system-view
2. Access the BGP view.
  bgp { as-number-plain | as-number-dot }
3. Set a confederation ID.
  confederation id { as-number-plain | as-number-dot }
4. Set the number of the sub-AS where other EBGP peers connected to the local AS resides.
  confederation peer-as { as-number-plain | as-number-dot } &<1-32>
  
  A confederation includes up to 32 sub-ASs. The parameter as-number used is valid for the confederation to which it belongs.
  
  You must run the confederation id and confederation peer-as commands for all the EBGP peers in a confederation, and specify the same confederation ID for them.
  
  An old speaker that has a 2-byte AS number cannot be in the same confederation with a new speaker that has a 4-byte AS number. Otherwise, a routing loop may occur. This is because the AS4_Path attribute does not support confederations.
Configure the compatibility of the confederation.
1. Access the system view.
  system-view
2. Access the BGP view.
  bgp { as-number-plain | as-number-dot }
3. Configure the routers to be compatible with the nonstandard AS confederation.
  confederation nonstandard
  
  By default, the configured confederation accords with RFC 3065.