3Com Switch 8800 Advanced Software V5 Configuration Guide

Configuring Graceful Restart 797
Before the restart, the GR Restarter originates Grace-LSA negotiation GR
capability. During the restart, the GR Helper continues to advertise its adjacency
with the GR Restarter.
After the restart, the GR Restarter will send an OSPF GR signal to its neighbor so
that the adjacency is not reset. In this way, the GR Restarter can restore its
adjacency with its neighbor upon receiving the responses from the latter.
Upon the reestablishment of the adjacency, the GR Restarter will update its
link-state database with all of its GR Capable neighbors and exchange routing
information with them. After that, the GR Restarter will update its own routing
table (forwarding table) based on the new routing information and delete the
stale routes. In this way, the OSPF routing convergence is complete.
Configuring Graceful
Restart
n
One device can act as both GR Restarter and GR Helper at the same time.
Graceful Restart configuration can be normally achieved by enabling the Graceful
Restart Capability. The time parameters can be configured if necessary, but under
normal circumstances the defaults should be used.
Configuring BGP-based
Graceful Restart
Follow these steps to configure BGP-based GR on the GR Restarter and the GR
Helper:
n
■ In general the maximum time allowed for the peer to reestablish a BGP session
should be less than the Holdtime carried in the OPEN message. Upon detection
of the termination of the session, the GR Helper will wait for a period of time
as specified by the GR Time before it reestablishes the BGP session.
■ The End-of-RIB marker can be used to indicate that the updated routing
information has been sent.
Configuring OSPF-based
Graceful Restart
Configuring OSPF-based GR Restarter
Follow these steps to configure the OSPF-based GR Restarter:
To do... Use the command... Remarks
Enter system view system-view -
Enable BGP, and enter its view bgp as-number Required
Disabled by default
Enable Graceful Restart
Capability for BGP
graceful-restart Required
Disabled by default
Configure the maximum time
allowed for the peer to
reestablish a BGP session
graceful-restart timer
restart timer
Optional
150 seconds by default
Configure the maximum time
to wait for the End-of-RIB
marker
graceful-restart timer
wait-for-rib timer
Optional
180 seconds by default
Note: End-of-RIB = End of Router-Information-Base