Cisco Cisco IOS Software Release 12.4(6)T
OSPF RFC 3623 Graceful Restart Helper Mode
How to Use OSPF RFC 3623 Graceful Restart Helper Mode to Manage the Graceful Restart Process of a Neighbor Router
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Cisco IOS Release 12.4(6)T
Helper Mode Exit
The helper router stops performing helper mode for its neighbor when one of the following events occur:
•
The grace-LSA that was originated by the restarting router is flushed, to signify that the restarting
router has exited the graceful restart process successfully.
router has exited the graceful restart process successfully.
•
The grace period of the grace-LSA expires.
•
A change in link-state database contents indicates a network topology change, forcing the
termination of the graceful restart process.
termination of the graceful restart process.
For complete information regarding graceful restart functionality refer to RFC 3623:
http://www.ietf.org/rfc/rfc3623/txt
How to Use OSPF RFC 3623 Graceful Restart Helper Mode to
Manage the Graceful Restart Process of a Neighbor Router
Manage the Graceful Restart Process of a Neighbor Router
This section contains the following task:
•
(optional)
Disabling Graceful Restart Helper Mode and Configuring Strict LSA Checking
on the Helper Router
on the Helper Router
The graceful restart helper mode feature is enabled by default. It is not recommended to disable helper
mode because the disabled neighbor will detect the lost adjacency and the graceful restart process will
be terminated on the restarting neighbor router.
mode because the disabled neighbor will detect the lost adjacency and the graceful restart process will
be terminated on the restarting neighbor router.
The strict LSA checking feature allows a helper router to terminate the graceful restart process if it
detects a changed LSA that would cause flooding during the graceful restart process. Strict LSA
checking is disabled by default. You can enable strict LSA checking on an OSPF helper to have the router
terminate graceful restart when there is a change to an LSA that would be flooded to the restarting router.
You can configure strict LSA checking on both NSF-aware and NSF-capable routers; however, this
feature will become effective only when the router is in helper mode.
detects a changed LSA that would cause flooding during the graceful restart process. Strict LSA
checking is disabled by default. You can enable strict LSA checking on an OSPF helper to have the router
terminate graceful restart when there is a change to an LSA that would be flooded to the restarting router.
You can configure strict LSA checking on both NSF-aware and NSF-capable routers; however, this
feature will become effective only when the router is in helper mode.
Complete the steps in the following task to disable helper mode or enable strict LSA checking on the
NSF-aware (helper) router.
NSF-aware (helper) router.
SUMMARY STEPS
1.
enable
2.
configure terminal
3.
router ospf process-id [vrf vpn-name]
4.
nsf ietf helper disable
5.
nsf ietf helper strict-lsa-checking
6.
end
7.
show ip ospf [process-id]