99Supported OSPF featuresMultiprocessWith multiprocess support, multiple OSPF processes can run on a router simultaneously andindependently. Routing information interactions between different processes seem like interactionsbetween different routing protocols. Multiple OSPF processes can use the same RID.An interface of a router can only belong to a single OSPF process.AuthenticationOSPF supports authentication on packets. Only packets that pass the authentication are received.If hello packets cannot pass authentication, no neighbor relationship can be established.The authentication type for interfaces attached to a single area must be identical. Authenticationtypes include non-authentication, plaintext authentication, and MD5 ciphertext authentication. Theauthentication password for interfaces attached to a network segment must be identical.Active or standby failoverOSPF backs up necessary information of the AMB into the SMB. Once the AMB fails, the SMBbegins to work to ensure the normal operation of OSPF.OSPF backs up the following information:• All OSPF data to the SMB. OSPF must recover normal operation immediately upon the AMBfailure.• Only the OSPF configuration information. After active or standby switchover, OSPF performsGR to synchronize the LSDB with neighbors.The GR feature is mainly used for HA and does not interfere with any other routers.When a router shuts down, its neighbors delete it from their neighbor tables and inform otherrouters, resulting in SPF recalculation. If the router restarts within several seconds, it isunnecessary to perform SPF recalculation and reestablish adjacencies.To avoid unnecessary SPF calculation, when a router restarts, it will inform neighboring routersthe shutdown is temporary. Then these routers will not delete the router from their neighbor tables,and other routers have no idea about this restart.After recovering to normal, the router obtains the LSDB from neighboring routers through the GR-related synchronization mechanism.OSPF graceful restartFor GR information, see GR Overview in the High Availability Configuration Guide.After an OSPF GR Restarter restarts, it must perform the following tasks to re-synchronize its LSDBwith its neighbors:
