H3C Technologies H3C SR8800 - Manual (Page 164)

148
CLV Code Name PDU Type
132 IP Interface Address IIH, LSP
Supported IS-IS features
Multiple instances and processes
IS-IS supports multiple instances and processes. Multiple processes allow a IS-IS process to work in
concert with a group of interfaces. A router can run multiple IS-IS processes, and each process
corresponds to a unique group of interfaces.
For routers supporting VPN, each IS-IS process is associated with a VPN instance. The VPN instance is
also associated with interfaces of the process.
Active/Standby failover
The router supports active/standby failover for IS-IS. The data is copied from the active main board (AMB)
to the standby main board (SMB). Whenever the AMB is down, the SMB can switch to the active status
to run IS-IS.
The router supports only the Graceful Restart (GR) backup mode. GR backs up only the configuration of
IS-IS. After active/standby failover, IS-IS performs GR to synchronize the LSDB with neighbors.
IS-IS Graceful Restart
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 be GR capable.
• GR Helper—A neighbor of the GR Restarter. It helps the GR Restarter to complete the GR process.
After an IS-IS GR Restarter restarts, it must complete the following tasks to synchronize the LSDB with its
neighbors.
• Obtain IS-IS neighbor information without changing adjacencies.
• Obtain the LSDB.
To do so, the GR Restarter sends an OSPF GR signal to GR Helpers so that the GR Helpers keep their
adjacencies with the GR Restarter, and restores the neighbor table after receiving responses from
neighbors. The GR Restarter then synchronizes the LSDB with all GR capable neighbors, calculates routes,
updates its routing table and forwarding table, and removes stale routes. The IS-IS routing convergence
is complete.
IS-IS NSR
Non-stop Routing (NSR) is a new feature that overcomes the application limit of GR. It backs up IS-IS link
state information from the AMB to the SMB. When an active/standby switchover occurs, NSR can
complete link state recovery and route re-generation without requiring the cooperation of other routers.
IS-IS TE
IS-IS Traffic Engineering (TE) creates and maintains the Label Switched Path (LSP).
When creating the Constraint-based Routed LSP (CR LSP), MPLS needs to get the traffic attribute
information of all links in the local area. The Traffic Engineering information of links is obtained from
IS-IS.