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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
78-17058-01
Chapter 17 Configuring Flex Links
Configuring Flex Links
• A backup link does not have to be the same type (Fast Ethernet, Gigabit Ethernet, or port channel)
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 begins to forward traffic.
• STP is disabled on Flex Link ports. If STP is configured on the switch, Flex Links do not participate
in STP in all VLANs in which STP is configured. With STP not running, be sure that there are no
loops in the configured topology.\
Note STP is available only on NNIs.
Configuring Flex Links
Beginning in privileged EXEC mode, follow these steps to configure a pair of Flex Links:
This example shows how to configure an interface with a backup interface and to verify the
configuration:
Switch# configure terminal
Switch(conf)# interface fastethernet0/1
Switch(conf-if)# no shutdown
Switch(conf-if)# switchport backup interface fastethernet0/2
Switch(conf-if)# end
Switch# show interface switchport backup
Switch Backup Interface Pairs:
Active Interface Backup Interface State
------------------------------------------------------------------------------------------
FastEthernet0/1 FastEthernet0/2 Active Up/Backup Standby
FastEthernet0/3 FastEthernet0/4 Active Up/Backup Standby
Port-channel1 GigabitEthernet0/1 Active Up/Backup Standby
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Specify the interface, and enter interface configuration
mode. The interface can be a physical Layer 2 interface or
a port channel (logical interface). The port-channel range
is 1 to 48.
Step 3
no shutdown Enable the port, if necessary. By default, UNIs are
disabled, and NNIs are enabled.
Step 4
switchport backup interface interface-id Configure a physical Layer 2 interface (or port channel)
as part of a Flex Link pair with the interface. When one
link is forwarding traffic, the other interface is in standby
mode.
Step 5
end Return to privileged EXEC mode.
Step 6
show interface [interface-id] switchport backup Verify the configuration.
Step 7
copy running-config startup config (Optional) Save your entries in the switch startup
configuration file.