Configure Nonstop Forwarding Specific To Cisco For Ospf Version 2 - Cisco NCS 5500 Series Configuration Manuals

Configure Nonstop Forwarding Specific to Cisco for OSPF Version 2

not experience routing flaps. During failover, data traffic is forwarded through intelligent line cards while the
standby Route Processor (RP) assumes control from the failed RP. The ability of line cards to remain up
through a failover and to be kept current with the Forwarding Information Base (FIB) on the active RP is key
to the NSF operation.
Routing protocols, such as OSPF, run only on the active RP or DRP and receive routing updates from their
neighbor routers. When an OSPF NSF-capable router performs an RP failover, it must perform two tasks to
resynchronize its link-state database with its OSPF neighbors. First, it must relearn the available OSPF
neighbors on the network without causing a reset of the neighbor relationship. Second, it must reacquire the
contents of the link-state database for the network.
As quickly as possible after an RP failover, the NSF-capable router sends an OSPF NSF signal to neighboring
NSF-aware devices. This signal is in the form of a link-local LSA generated by the failed-over router. Neighbor
networking devices recognize this signal as a cue that the neighbor relationship with this router should not be
reset. As the NSF-capable router receives signals from other routers on the network, it can begin to rebuild
its neighbor list.
After neighbor relationships are reestablished, the NSF-capable router begins to resynchronize its database
with all of its NSF-aware neighbors. At this point, the routing information is exchanged between the OSPF
neighbors. After this exchange is completed, the NSF-capable device uses the routing information to remove
stale routes, update the RIB, and update the FIB with the new forwarding information. OSPF on the router
and the OSPF neighbors are now fully converged.
Configure Nonstop Forwarding Specific to Cisco for OSPF Version 2
This task explains how to configure OSPF NSF specific to Cisco on your NSF-capable router. This task is
optional.
Before you begin
OSPF NSF requires that all neighbor networking devices be NSF aware, which happens automatically after
you install the software image on the router. If an NSF-capable router discovers that it has non-NSF-aware
neighbors on a particular network segment, it disables NSF capabilities for that segment. Other network
segments composed entirely of NSF-capable or NSF-aware routers continue to provide NSF capabilities.
Note
The following are restrictions when configuring nonstop forwarding:
• OSPF Cisco NSF for virtual links is not supported.
• Neighbors must be NSF aware.
SUMMARY STEPS
1. configure
2. router ospf process-name
3. router-id { router-id }
4. Do one of the following:
Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.3.x
74
• nsf cisco
• nsf cisco enforce global
Implementing OSPF