726 BigIron RX Series Configuration Guide53-1001986-01Displaying OSPF information25 Displaying OSPF virtual link informationUse the show ip ospf virtual link command to display OSPF virtual link information. The outputbelow represents the virtual links configured in Figure 109.Syntax: show ip ospf virtual link []The parameter displays the table beginning at the specified entry number.OSPF graceful restartWith OSPF graceful restart enabled, a restarting router sends special LSAs, called grace-lsas, to itsneighbors. These LSAs are sent to neighbors either before a planned OSPF restart or immediatelyafter an unplanned restart. A grace LSA contains a grace period value that the requesting routersasks its neighbor routers to use for the existing routes, to and through the router after a restart. Therestarting router comes up, it continues to use its existing OSPF routes to forward packets. In thebackground, it re-establishes OSPF adjacencies with its neighboring router, relearns all OPSF LSAs,recalculates its OSPF routes, and replaces them with new routes as necessary. Once the restartingrouter relearns all OSPF routes, it flushes the grace LSAs from the network, informing the helperrouters of the completion of the restart process. If the restarting router does not re-establishadjacencies with the helper router within the restart time, the helper router stops the helpingfunction and flushes the stale OSPF routes.Configuring OSPF graceful restartTo configure OSPF Graceful Restart on a router, the restarting router and its directly connectedOSPF peers must be configured with Graceful Restart.BigIron RX(config)#router ospfBigIron RX(config-ospf-router)#area 0BigIron RX(config-ospf-router)#graceful-restartgraceful-restartEnabling and disabling OSPF helperWhen OSPF is enabled, the helper mode is enabled by default. OSPF routers that do not havegraceful restart enabled will act as if the graceful restart helper is enabled. To prevent the gracefulrestart from performing its function, disable it by entering the following command.BigIron RX(config-ospf-router)#graceful-restart helper-disableSyntax: [no] graceful-restart helper disableUse the no form of the command to re-enable the graceful restart helper.BigIron RX#show ip ospf virtual linkIndx Transit Area Router ID Transit(sec) Retrans(sec) Hello(sec)1 1 131.1.1.10 1 5 10Dead(sec) events state Authentication-Key40 1 ptr2ptr NoneMD5 Authentication-Key: NoneMD5 Authentication-Key-Id: NoneMD5 Authentication-Key-Activation-Wait-Time: 300
