Cisco Cisco IOS Software Release 12.0(13)S7

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This document focuses on nonstop forwarding (NSF) for OSPFv2 in Cisco IOS software, using the IETF 
standardized graceful restart functionality that is described in RFC 3623. Under very specific situations, 
a router may undergo certain well-known failure conditions that should not affect packet forwarding 
across the switching platform. NSF capability allows for the forwarding of data packets to continue 
along routes that are already known, while the routing protocol information is being restored. This 
capability is useful in cases in which there is a component failure (for example, a Route Processor [RP] 
crash with a backup RP taking over) or in which there is a scheduled hitless software upgrade.

Prior to RFC 3623, Cisco implemented Cisco-proprietary NSF, referred to as Cisco NSF. The OSPF RFC 
3623 Graceful Restart feature allows you to configure IETF NSF in multivendor networks. Configuring 
IETF NSF increases the availability of your network by allowing OSPF routers to stay on the forwarding 
path even as their OSPF software is restarted. This document refers to the two forms of NSF as Cisco 
NSF and IETF NSF. The OSPF RFC 3623 Graceful Restart feature is the latest addition to the Cisco High 
Availability portfolio.

Your Cisco IOS software release may not support all of the features documented in this module. To reach 
links to specific feature documentation in this module and to see a list of the releases in which each feature is 
supported, use the 

.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS 
software image support. To access Cisco Feature Navigator, go to 

. An 

account on Cisco.com is not required.