Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 752)

724 Multi-Service IronWare Routing Configuration Guide
53-1003033-02
IPv6 IS-IS Non-Stop Routing
IPv6 IS-IS Non-Stop Routing (NSR) enables the IPv6 IS-IS router to maintain topology and data flow
to avoid re-convergence in the network during a processor switchover or hitless-reload event. The
IS-IS Bidirectional Forwarding Detection (BFD) sessions survive the switchover and hitless-reload
conditions. In general, a router restart causes its peer to remove the routes originated from the
router and reinstalls them. This IS-IS NSR feature enables the router to maintain neighbors and LSA
database with its peer on the event of a router restart. This feature is compatible with IPv4 IS-IS
NSR.
NOTE
IPv6 IS-IS NSR is independent of Graceful Restart (GR) and GR help role mechanisms.
Limitations
• The IS-IS over GRE tunnel feature does not support IS-IS NSR. The GRE tunnel interface types
are not supported.
• The IS-IS shortcuts are not supported because they depend on the MPLS tunnel.
• If the IS-IS hellos are forwarded at Layer 2 and the device executes a hitless-reload, hellos will
not be forwarded for a brief time. The IS-IS adjacencies are lost for 12 seconds and there will
be data traffic loss.
• The configuration events that occur close to switchover or hitless-reload may get lost due to CLI
synchronization issues.
• The neighbor or interface state changes close to switchover or hitless-reload cannot be
handled.
• The IS-IS neighbor hold timer is restarted upon IS-IS NSR switchover or hitless-reload.
• The traffic counters are not synchronized because the neighbor and LSP database counters
are recalculated on the standby module during synchronization.
• With IS-IS NSR enabled, after switchover or hitless-reload to standby MP, IS-IS routes, LSP
database and neighbor adjacencies are maintained so that there will be no loss of existing
traffic to the IS-IS destinations.
• The IS-IS NSR hitless failover event may not be completely invisible to the network because,
after switchover, additional flooding of CSNP packets will occur in the directly connected
neighbors.
Configuring IS-IS NSR
To globally enable IS-IS NSR, enter the following commands.
Brocade(config)# router isis
Brocade(config-isis-router)# nonstop-routing
To globally disable IS-IS NSR, enter the following commands.
Brocade(config)# router isis
Brocade(config-isis-router)# no nonstop-routing
Syntax: [no] nonstop-routing