To configure an interface as a secondary or dial backup, use the backup interface command in interface configuration mode. To disable the interface from serving as a backup, use the no form of this command.

Cisco 7200 Series and Cisco 7500 Series Routers Only

backup interface slot/port-adapter/port

no backup interface slot/port-adapter/port

Other Cisco Routers

backup interface type number

no backup interface type number

Syntax Description

slot/port-adapter/port The chassis slot, port adapter, and port number of the interface to configure as a backup. Include a slash (/) between slot, port-adapter, and port (for example, 1/1/1). See your hardware installation manual for the specific slot, port adapter, and port numbers.
Type and port number of the interface being configured as a backup.

Command Default

This command is disabled by default.

Command Modes

Interface configuration

Command History

Release Modification
11.0 This command was introduced.
12.2(33)SRB1 This command was integrated into Cisco IOS Release 12.2(33)SRB1.

Usage Guidelines

The interface you define with this command can back up only one other interface.

Routers support only serial and ISDN backup interfaces. Access servers support both asynchronous and serial backup interfaces.

In Cisco IOS Release 12.2(33)SRB1 and later releases, you can configure a backup interface for Gigabit Ethernet on the Cisco 7600 router. The configurations on the primary and backup interfaces must match or the backup interface does not work. Note, however, that if the interface configuration includes the xconnect command, you must specify a different virtual circuit ID (VCID) on the primary and backup interfaces.


The following example sets serial 1 as the backup line to serial 0:

interface serial 0
 backup interface serial 1

The following example sets gigabitEthernet4/0/1 as the backup interface for gigabitEthernet3/0/1 on the Cisco 7600 router:

interface gigabitEthernet 3/0/1
  backup interface gigabitEthernet 4/0/1

Related Commands

Command Description
xconnect Configures a pseudowire for transporting data over the network.

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