Cisco Systems RSP8 Configuring Nonstop Forwarding (NSF)

Route Switch Processor (RSP8) Installation and Configuration Guide

OL-4920-02

Enabling High Availability Features

Configuring Nonstop Forwarding (NSF)

Cisco Nonstop Forwarding (NSF) always runs together with SSO. If you have not already configured

SSO,refer to the “Configuring a Stateful Switchover (SSO)” section on page 49. Cisco NSF is supported

by the BGP, OSPF, and IS-IS protocols for routing and by Cisco Express Forwarding (CEF) for

forwarding. Of the routing protocols, BGP, 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

necessaryactions 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 activeand the standby RSP to recover route information following a switchover instead of

information received from peer devices.

Adevice 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

protocolsrebuild the Routing Information Base (RIB) tables. Once the routing protocols have converged,

CEFupdates the FIB table and removesstale route entries. CEF, in turn, updates the line cards with the

new FIB information.

See the following sections for the NSF feature. Each task in the list is identified as either required or

optional.

•Configuring CEF NSF, page52 (required)

•Configuring BGP NSF, page52 (required)

•Configuring OSPF NSF, page53 (required)

•Configuring IS-IS NSF, page53 (required)

•Verifying CEF NSF, page54 (optional)

•Verifying BGP NSF, page55 (optional)

•Verifying OSPF NSF, page56 (optional)

•Verifying IS-IS NSF, page56 (optional)

•Troubleshooting NSF Features, page58 (optional)

•BGP NSF Configuration Example, page59 (optional)

•BGP NSF Neighbor Device Configuration Example, page59 (optional)

•OSPF NSF Configuration Example, page59 (optional)

•IS-IS NSF Configuration Example, page59 (optional)

The CEF NSF feature operates by default while the networking device is running in SSO mode. No

configuration is necessary.

Note You must configure BGP graceful restart on all peer devices participating in BGP NSF.