Cisco Cisco IOS Software Release 12.2(20)S
Cisco Nonstop Forwarding
Information About Cisco Nonstop Forwarding
4
Stateful Switchover
Cisco NSF Routing and Forwarding Operation
Cisco NSF is supported by the BGP, EIGRP, OSPF, and IS-IS protocols for routing and by Cisco Express
Forwarding (CEF) for forwarding. Of the routing protocols, BGP, EIGRP, OSPF, and IS-IS have been
enhanced with NSF-capability and awareness, which means that routers running these protocols can
detect a switchover and take the necessary actions to continue forwarding network traffic and to recover
route information from the peer devices. The IS-IS protocol can be configured to use state information
that has been synchronized between the active and the standby RP to recover route information following
a switchover instead of information received from peer devices.
Forwarding (CEF) for forwarding. Of the routing protocols, BGP, EIGRP, OSPF, and IS-IS have been
enhanced with NSF-capability and awareness, which means that routers running these protocols can
detect a switchover and take the necessary actions to continue forwarding network traffic and to recover
route information from the peer devices. The IS-IS protocol can be configured to use state information
that has been synchronized between the active and the standby RP to recover route information following
a switchover instead of information received from peer devices.
In this document, a networking device is said to be NSF-aware if it is running NSF-compatible software.
A device is said to be NSF-capable if it has been configured to support NSF; therefore, it would rebuild
routing information from NSF-aware or NSF-capable neighbors.
A device is said to be NSF-capable if it has been configured to support NSF; therefore, it would rebuild
routing information from NSF-aware or NSF-capable neighbors.
Each protocol depends on CEF to continue forwarding packets during switchover while the routing
protocols rebuild the Routing Information Base (RIB) tables. Once the routing protocols have converged,
CEF updates the FIB table and removes stale route entries. CEF, in turn, updates the line cards with the
new FIB information.
protocols rebuild the Routing Information Base (RIB) tables. Once the routing protocols have converged,
CEF updates the FIB table and removes stale route entries. CEF, in turn, updates the line cards with the
new FIB information.
lists the routing protocol and CEF support in Cisco NSF.
Table 1
Routing Protocol and CEF Support in Cisco NSF
Protocol
Platform
NSF Support in Cisco IOS Software Release
12.0(22)S
12.0(23)S
12.0(24)S
12.2(18)S
12.2(28)SB
12.2(33)SRA
BGP
Cisco 7200
Yes
1
Yes
Yes
No
2
No No
Cisco 7304
No
No
No
No
Yes
No
Cisco 7500
Yes
Yes
Yes
Yes
No
No
Cisco 7600
No
No
No
No
No
Yes
Cisco 10000
Yes
Yes
Yes
No
Yes
No
Cisco 12000
Yes
Yes
Yes
No
No
No
OSPF
Cisco 7200
Yes
Yes
Yes
No
No
No
Cisco 7304
No
No
No
No
Yes
No
Cisco 7500
Yes
Yes
Yes
Yes
No
No
Cisco 7600
No
No
No
No
No
Yes
Cisco 10000
Yes
Yes
Yes
No
No
No
Cisco 12000
Yes
Yes
Yes
No
No
No
IS-IS
Cisco 7200
Yes
Yes
Yes
No
No No
Cisco 7304
No
No
No
No
Yes
No
Cisco 7500
Yes
Yes
Yes
Yes
No
No
Cisco 7600
No
No
No
No
No
Yes
Cisco 10000
Yes
Yes
Yes
No
Yes
No
Cisco 12000
Yes
Yes
Yes
No
No
No