Cisco WS-C3560X-24T-L Command Reference - Page 654
switchport backup interface
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switchport backup interface Chapter 2 Catalyst 3560 Switch Cisco IOS Commands switchport backup interface Use the switchport backup interface interface configuration command on a Layer 2 interface to configure Flex Links, a pair of interfaces that provide backup to each other. Use the no form of this command to remove the Flex Links configuration. switchport backup interface {interface-id} no switchport backup Syntax Description interface-id Specify the Layer 2 interface to act as a backup link to the interface being configured. The interface can be a physical interface or port channel. The port-channel range is 1 to 48. Note Though visible in the command-line help, VLAN interfaces are not supported. Defaults The default is to have no Flex Links defined. Command Modes Interface configuration Command History Release 12.2(20)SE Modification This command was introduced. Usage Guidelines With Flex Links configured, one link acts as the primary interface and forwards traffic, while the other interface is in standby mode, ready to begin forwarding traffic if the primary link shuts down. The interface being configured is referred to as the active link; the specified interface is identified as the backup link. The feature provides an alternative to the Spanning Tree Protocol (STP), allowing users to turn off STP and still retain basic link redundancy. • This command is available only for Layer 2 interfaces. • You can configure only one Flex Link backup link for any active link, and it must be a different interface from the active interface. • An interface can belong to only one Flex Link pair. An interface can be a backup link for only one active link. An active link cannot belong to another Flex Link pair. • A backup link does not have to be the same type (Fast Ethernet or Gigabit Ethernet, for instance) as the active link. However, you should configure both Flex Links with similar characteristics so that there are no loops or changes in behavior if the standby link takes over traffic forwarding. 2-622 Catalyst 3560 Switch Command Reference 78-16405-05