R3303-HP HSR6800 Routers Layer 3 - IP Routing Configuration Guide

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CLV Code Name PDU T
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132 IP Interface Address IIH, LSP
Supported IS-IS features
Multiple instances and processes
IS-IS supports multiple instances and processes. Multiple processes allow an 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, which means the VPN
instance is also associated with interfaces of the process.
Active/Standby failover
In standalone mode, IS-IS backs up necessary data from the active MPU to the standby MPU. Whenever
the active MPU is down, the standby MPU can switch to the active status to run IS-IS.
In IRF mode, IS-IS backs up necessary data from the global active MPU to the global standby MPU.
Whenever the global active MPU is down, the global standby MPU can switch to the active status to run
IS-IS.
IS-IS supports the Graceful Restart (GR) backup mode:
• In standalone mode, GR backs up only the configuration of IS-IS. After active/standby MPU failover,
IS-IS performs graceful restart to synchronize the LSDB with neighbors.
• In IRF mode, GR backs up only the configuration of IS-IS. After global active/standby MPU failover,
IS-IS performs graceful restart to synchronize the LSDB with neighbors.
IS-IS GR
GR ensures the continuity of packet forwarding when a routing protocol restarts, an active/standby MPU
switchover in standalone mode occurs, or a global active/standby MPU switchover in IRF mode 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 complete these tasks, 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 then complete.
IS-IS NSR
Nonstop routing (NSR) is a new feature that overcomes the application limit of GR:
• In standalone mode, NSR backs up IS-IS link state information from the active MPU to the standby
MPU. When an active/standby MPU switchover occurs, NSR can complete link state recovery and
route regeneration without requiring the cooperation of other devices.