Note	Effective with Cisco IOS Release 12.0(32)S, the nsf (OSPF) command has been replaced by the nsf cisco command. See the nsf cisco command for more information.

To configure Cisco nonstop forwarding (NSF) operations for Open Shortest Path First (OSPF), use the nsf command in router configuration mode. To disable Cisco NSF for OSPF, use the no form of this command.

Syntax Description

Command Default

This command is disabled by default; therefore, NSF operations for OSPF is not configured.

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

The user must configure NSF operation for OSPF only if a router is expected to perform NSF during restart. For users to have full NSF benefits, all OSPF neighbors of the specified router must be NSF-aware.

If neighbors that are not NSF-aware are detected on a network interface, NSF restart is aborted on the interface; however, NSF restart will continue on other interfaces. This functionality applies to the default NSF mode of operation when NSF is configured.

If the user configures the optional enforce globalkeywords, NSF restart will be canceled for the entire process when neighbors that are not NSF-aware are detected on any network interface during restart. NSF restart will also be canceled for the entire process if a neighbor adjacency reset is detected on any interface or if an OSPF interface goes down. To revert to the default NSF mode, enter the no nsf enforce global command.

Related Commands

To enable Cisco nonstop forwarding (NSF) operations on a router that is running Open Shortest Path First (OSPF), use the nsf cisco command in router configuration mode. To return to the default, use the no form of this command.

Syntax Description

Command Default

Cisco NSF restarting mode is disabled. Cisco NSF helper mode is enabled.

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

For Cisco IOS Release 12.0(32)S and later releases, this command replaces the nsf (OSPF) command.

This command enables Cisco NSF on an OSPF router. When NSF is enabled on a router, the router is NSF-capable and will operate in restarting mode.

If a router is expected to cooperate with a neighbor that is doing an NSF graceful restart only, the neighbor router must be running a Cisco software release that supports NSF but NSF need not be configured on the router. When a router is running a Cisco software release that supports NSF, the router is NSF-aware.

By default, neighboring NSF-aware routers will operate in NSF helper mode during a graceful restart. To disable Cisco NSF helper mode on an NSF-aware router, use this command with the disable keyword. To reenable helper mode after explicitly disabling helper mode on an NSF-aware router, use the no nsf cisco helper disable command.

If neighbors that are not NSF-aware are detected on a network interface during an NSF graceful restart, restart is aborted on that interface only and graceful restart will continue on other interfaces. To cancel restart for the entire OSPF process when neighbors that are not NSF-aware are detected during restart, configure this command with the enforce global keywords.

Note	The NSF graceful restart will also be canceled for the entire process when a neighbor adjacency reset is detected on any interface or when an OSPF interface goes down.

Related Commands

To configure Internet Engineering Task Force (IETF) nonstop forwarding (NSF) operations on a router that is running Open Shortest Path First (OSPF), use the nsf ietf command in router configuration mode. To return to the default, use the no form of this command.

Syntax Description

Command Default

IETF NSF graceful restart mode is disabled. IETF NSF helper mode is enabled.

Command Modes

Router configuration (config-router)

Command History

Usage Guidelines

This command enables IETF NSF on an OSPF router. When NSF is enabled on a Cisco router, the router is NSF-capable and will operate in restarting mode.

If a router is expected to cooperate with a neighbor that is doing an NSF graceful restart only, the neighbor router must be running a Cisco software release that supports NSF but NSF need not be configured on the router. When a router is running a Cisco software release that supports NSF, the router is NSF-aware.

By default, neighboring NSF-aware routers will operate in NSF helper mode during a graceful restart. To disable IETF NSF helper mode on an NSF-aware router, use this command with the disable keyword. To reenable helper mode after explicitly disabling helper mode on an NSF-aware router, use the no nsf ietf helper disable command.

Strict LSA checking allows a router in IETF NSF helper mode to terminate the graceful restart process if it detects a changed LSA that would cause flooding during the graceful restart process. You can configure strict LSA checking on NSF-aware and NSF-capable routers but it is effective only when the router is in helper mode.

Related Commands