Bgp Gr - HP 6125G Configuration Manual

Figure 57 Confederation network diagram
AS 100
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 as follows:
When changing an AS into a confederation, you must reconfigure your routers.
•
• The topology is 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 a Master/Slave
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.
The following describes the BGP routing convergence process:
To establish a BGP session with a peer, a BGP GR Restarter sends an Open message with GR
1.
capability to the peer.
Upon receipt of this message, the peer is aware that the sending router is capable of Graceful
2.
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.
When a Master/Slave switchover occurs on the GR Restarter, sessions on it will go down. Then,
3.
GR-capable peers will mark all routes associated with the GR Restarter as stale. However, during
the configured GR Time, they still use these routes for packet forwarding.
After the restart is completed, the GR Restarter will reestablish GR sessions with its peers and send
4.
a new GR message, notifying the completion of restart. Routing information is exchanged between
them for the GR Restarter to create a new routing table and forwarding table and have stale
routing information removed. Then the BGP routing convergence is complete.
AS 65002
EBGP
EBGP
IBGP
AS 200
AS 65003
EBGP
IBGP
IBGP
AS 65004
129