Reference Guide

Layer 2 | 557
FTOS supports only Gigabit and 10-Gigabit ports and port channels as primary/backup interfaces in
redundant pairs. (A port channel is also referred to as a Link Aggregation Group (LAG). Refer to Port
Channel Interfaces for more information.)
In a redundant pair, any combination of physical and port-channel interfaces is supported as the two
interfaces in a redundant pair. For example, you can configure a static (without LACP) or dynamic (with
LACP) port-channel interface as either the primary or backup link in a redundant pair with a Gigabit
interface.
To ensure that existing network applications see no difference when a primary interface in a redundant pair
transitions to the backup interface, be sure to apply identical configurations of other traffic parameters to
each interface.
If you remove an interface in a redundant link (remove the line card of a physical interface or delete a port
channel with the
no interface port-channel command), the redundant pair configuration is also removed.
Important Points about Configuring Redundant Pairs
• An interface cannot be used as a backup for more than one interface; an interface can have no more
than one backup. A backup interface cannot have a backup interface.
• The active and standby/backup interfaces do not have to be of the same type (1G, 10G, etc).
• You may not enable any Layer 2 protocol on an interface in a redundant pair or on a port connected to
a redundant interface.
• When you use a static or dynamic port channel as the active or backup interface in a redundant pair, the
following conditions apply:
• If you use two port-channel interfaces with different configurations in a redundant pair, traffic is
transmitted in the same way following a transition to the backup interface. There is no difference
in performance. For example, two port channels in a redundant pair can contain a different number
and type of member ports or use different LACP modes.
• There are no requirements on the number or type of links in a port channel.
• There are no requirements on the location of the member links in a port channel, such as on the
same line card or stacked device.
• If you use a dynamic port channel in a redundant pair, LACP operation on the port channel is not
affected by its status as the active or backup interface.
• If you manually shut down a port channel that is the active interface in a redundant pair (
shutdown
command), the status of the port channel transitions to DOWN and the backup interface becomes
active.
• If the number of member links with an “oper up” status is less than the minimum number of
required links configured for a port channel that is the active interface in a redundant pair, the
status of the port channel transitions to DOWN and the backup interface becomes active.
• If a static or dynamic port channel is used in a redundant pair, the port channel cannot be used as a
member of a failover group in shared LAG state tracking (refer to the LACP chapter).
• A dynamic port channel that is used in a redundant pair can participate in hitless LACP (refer to
Configure LACP as Hitless in LACP chapter).