H3C Technologies H3C S12500 Series Switches - Manual (Page 88)

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An interface of a router can only belong to a single OSPF process.
Authentication
OSPF can authenticate OSPF packets. Only packets that pass the authentication are received. If an
incoming hello packet cannot pass authentication, the neighbor relationship cannot be established.
The authentication type for interfaces attached to a single area must be identical. Authentication types
include non-authentication, plaintext authentication, and MD5 ciphertext authentication. The
authentication password for interfaces attached to a network segment must be identical.
Active/Standby failover
OSPF backs up necessary information from the active main processing unit (MPU) to the standby MPU.
Once the active MPU fails, the standby MPU begins to work to ensure the normal operation of OSPF.
OSPF provides the following backup modes:
• Non-stop Routing (NSR), which backs up all OSPF data to the standby MPU to make sure that OSPF
recovers immediately upon an active/standby switchover.
• Graceful Restart (GR), which backs up only the OSPF configuration information to the standby MPU.
Once an active/standby switchover occurs, OSPF performs GR to synchronize the LSDB with
neighbors.
OSPF GR
GR ensures the continuity of packet forwarding when a routing protocol restarts or an active/standby
switchover occurs:
• GR restarter—Graceful restarting router. It must have GR capability.
• GR helper—A neighbor of the GR restarter. It helps the GR restarter to complete the GR process.
After an OSPF GR restarter restarts, it must perform the following tasks:
• Obtain OSPF neighbor information.
• Obtain the LSDB.
Before restart, the GR restarter negotiates GR capability with GR helpers. During the restart of the GR
restarter, GR helpers still advertise their adjacencies with the GR restarter. After restart, the GR restarter
sends GR helpers an OSPF GR signal so that the GR helpers do not reset their neighbor relationships with
the GR restarter. Upon receiving responses from neighbors, the GR restarter creates the neighbor
relationships.
After that, the GR restarter synchronizes the LSDB with GR-capable neighbors, updates its routing table
and forwarding table, and removes stale routes.
OSPF NSR
With OSPF NSR, the active MPU and the standby MPU have consistent data information, which includes
the system operational data, and OSPF-related static and dynamic data. Upon an active/standby
switchover, the standby MPU takes over all services from the active MPU seamlessly without impacting
other services.
TE and DS-TE
OSPF Traffic Engineering (TE) provides for the establishment and maintenance of Label Switched Paths
(LSPs) of TE.
When establishing Constraint-based Routed LSPs (CR LSPs), MPLS obtains the TE information of links in
the area through OSPF.