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Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 19 Configuring Flex Links and MAC Address-Table Move Update
Configuring Flex Links
Configuration Guidelines
Follow these guidelines to configure Flex Links and associated features:
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 Links pair. An interface can be a backup link for only one
active link, but an active link cannot belong to another Flex Links pair.
Neither of the links can be a port that belongs to an EtherChannel. However, you can configure two
port channels (EtherChannel logical interfaces) as Flex Links. Moreover, you can configure a port
channel and a physical interface as Flex Links, with either the port channel or the physical interface
as the active link.
The types (Fast Ethernet, Gigabit Ethernet, or port channel) of the backup link and the active link
can differ. However, you should configure both Flex Links with similar characteristics so that no
loops exist or changes occur in behavior if the standby link begins to forward traffic.
STP is disabled on Flex Links ports. A Flex Links port does not participate in STP, even if the
VLANs present on the port are configured for STP. When STP is not enabled, ensure that no loops
exist in the configured topology.
Configure any static MAC addresses on a Flex Links member interface after enabling Flex Links.
Follow these guidelines to configure VLAN load balancing on the Flex Links feature. For Flex Links
VLAN load balancing, you must choose the preferred VLANs on the backup interface.
Set switchport backup interface interface-id preemption mode to forced. A default value of 35
seconds is used as the delay timeout. You cannot configure switchport backup interface
interface-id preemption mode on the interface. So, mode bandwidth and off cannot be configured.
Adjust the delay time with the switchport backup interface interface-id preemption delay
delay-time command.
Configuring Flex Links
To configure a pair of Flex Links, perform this task:
Command Purpose
Step 1 Switch# configure terminal Enters global configuration mode.
Step 2 Switch(conf)# interface interface-id Specifies the interface, and enters interface configuration
mode. The interface might be a physical Layer 2 interface
or a port channel (logical interface). The port channel
range is 1 to 64.
Step 3 Switch(conf-if)# switchport backup interface
interface-id Configures a physical Layer 2 interface (or port channel)
as part of a Flex Links pair with the interface. When one
link is forwarding traffic, the other interface is in standby
mode.
Step 4 Switch(conf-if)# end Returns to privileged EXEC mode.
Step 5 Switch# show interface [interface-id] switchport
backup Verifies the configuration.
Step 6 Switch# copy running-config startup config (Optional) Saves your entries in the switch startup
configuration file.