H3C Technologies H3C S10500 Series Switches - Manual (Page 179)

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Configuring IS-IS GR
Restarting IS-IS on a router causes network disconnections and route reconvergence.
With the Graceful Restart (GR) feature, the restarting router—known as the GR Restarter—can notify the
event to its GR capable neighbors. GR capable neighbors—known as the GR Helpers—will keep their
adjacencies with the router within a configurable GR interval. After the restart, the router contacts its
neighbors to retrieve its routing table.
During this process, the network keeps stable.
Follow these steps to configure GR on the GR Restarter and GR Helper, respectively:
To do… Use the command… Remarks
Enter system view system-view —
Enable IS-IS, and enter
IS-IS view isis [ process-id ] [ vpn-instance
vpn-instance-name ] Required
Disabled by default
Enable the GR capability
for IS-IS
graceful-restart
Required
Disabled by default
Set the Graceful Restart
interval
graceful-restart interval timer
Required
300 seconds by default
The Graceful Restart interval is set as the
holding time in the hello PDUs. Within the
interval, the neighbors will keep their
adjacency with the GR Restarter.
Suppress the SA bit during
restart
graceful-restart suppress-sa
Optional
By default, the SA bit is not suppressed.
By enabling the GR Restarter to suppress the
Suppress-Advertisement (SA) bit in the hello
PDUs, the neighbors will still advertise their
adjacency with the GR Restarter.
Configuring IS-IS FRR
NOTE:
•
Do not use FRR and BFD at the same time. Otherwise, FRR may fail to take effect.
• The automatic backup next hop calculation of FRR and that of TE are mutually exclusive.
Introduction
When a link fails, the packets on the path are discarded, or a routing loop occurs until IS-IS completes
the routing convergence based on the new network topology.
You can enable IS-IS fast reroute (FRR) to reduce traffic recovery time.