Cisco Cisco IOS Software Release 12.0(23)S

This document describes the Cisco Nonstop Forwarding (NSF) feature in Cisco IOS Release 12.0(23)S. 
It includes the following sections:

Throughout this document, the term “Route Processor” (RP) is used to describe the route processing 
engine on all networking devices, regardless of the platform designation, unless otherwise noted. For 
example, on the Cisco 10000 series Internet router the RP is referred to as the Performance Routing 
Engine (PRE), on the Cisco 12000 series Internet router the RP is referred to as the Gigabit Route 
Processor (GRP), and on the Cisco 7500 series router the RP is referred to as the Route Switch Processor 
(RSP).

Cisco NSF works with the Stateful Switchover (SSO) feature in Cisco IOS software. SSO is a 
prerequisite of Cisco NSF. NSF works with SSO to minimize the amount of time a network is unavailable 
to its users following a switchover. The main objective of Cisco NSF is to continue forwarding IP packets 
following a route processor (RP) switchover. 

12.0(22)S

This feature was introduced.

12.0(23)S

Support was added for 1xGE and 3xGE line cards on the 

For platforms supported in Cisco IOS Release 12.0(22)S and 12.0(23)S, consult Cisco Feature 
Navigator.