Configuration Guidelines - Cisco Catalyst 4500 series Administration Manual

Configuring Flex Links

Configuration Guidelines

Follow these guidelines to configure Flex Links and associated features:
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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.
Configuring Flex Links
To configure a pair of Flex Links, perform this task:
Command
Step 1
Switch# configure terminal
Step 2
Switch(conf)# interface interface-id
Step 3
Switch(conf-if)# switchport backup interface
interface-id
Step 4
Switch(conf-if)# end
Step 5
Switch# show interface [interface-id] switchport
backup
Step 6
Switch# copy running-config startup config
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
23-6
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.
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.
Chapter 23 Configuring Flex Links and MAC Address-Table Move Update
Purpose
Enters global configuration mode.
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.
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.
Returns to privileged EXEC mode.
Verifies the configuration.
(Optional) Saves your entries in the switch startup
configuration file.
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