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Catalyst 3560 Switch Command Reference
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Chapter 2 Catalyst 3560 Switch Cisco IOS Commands
switchport backup interface
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
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
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.
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.
Release Modification
12.2(20)SE This command was introduced.
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