1-14
Confederation
Confederation is another method to deal with growing iBGP connections in ASs. It splits an AS into
multiple sub-ASs. In each sub-AS, iBGP peers are fully meshed, and intra-confederation eBGP
connections are established between sub-ASs, as shown below:
Figure 1-15
Confederation network diagram
From the perspective of a non-confederation BGP speaker, it needs not know sub-ASs in the
confederation. The ID of the confederation is the number of the AS. In the above figure, AS 200 is the
confederation ID.
The deficiency of confederation is: when changing an AS into a confederation, you need to reconfigure
your routers, and the topology will be changed.
In large-scale BGP networks, both route reflector and confederation can be used.
BGP GR
z
For GR (Graceful Restart) information, refer to
GR Overview
in the
High Availability Volume
.
z
The 4800G series switches are centralized devices that support IRF. They can act as a GR Helper
before forming an IRF; they can form a distributed chassis switch in a logical sense and act as a
GR Restarter after forming an IRF. Active and standby switchover in this document refers to the
switching of the master for IRF devices.
1) To establish a BGP session with a peer, a BGP GR Restarter sends an OPEN message with GR
capability to the peer.
2) Upon receipt of this message, the peer is aware that the sending router is capable of Graceful
Restart, and sends an OPEN message with GR Capability to the GR Restarter to establish a GR
