H3C Technologies H3C SR8800 - Manual (Page 222)

206
NOTE:
After route reflection is disabled between clients, routes can still be reflected between a client and a
non-client.
Confederation
Confederation is another method to manage 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 in
Figure 85 :
Figure 85 Confederation network diagram
A non-confederation BGP speaker is not required to 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 must reconfigure
your routers, and the topology will be changed.
In large-scale BGP networks, both route reflector and confederation can be used.
BGP GR
Graceful Restart (GR) ensures the continuity of packet forwarding when BGP restarts or an
active/standby switchover occurs:
• GR Restarter—Graceful restarting router. It must be GR capable.
• GR Helper—A neighbor of the GR Restarter. It helps the GR Restarter to complete the GR process.
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
session. If neither party has the GR capability, the session established between them will not be GR
capable.
AS 100
EBGP
IBGP
IBGP
IBGP
EBGP EBGP
AS 65002 AS 65003
AS 65004
AS 200