Reference Guide

Interfaces | 421
Loopback Interfaces
A Loopback interface is a virtual interface in which the software emulates an interface. Packets routed to it
are processed locally. Since this interface is not a physical interface, you can configure routing protocols
on this interface to provide protocol stability. You can place Loopback interfaces in default Layer 3 mode.
To configure a Loopback interface, use the following command in the CONFIGURATION mode:
To view Loopback interface configurations, use the
show interface loopback number command in the EXEC
mode.
To delete a Loopback interface, use the
no interface loopback number command syntax in the
CONFIGURATION mode.
Many of the same commands found in the physical interface are found in Loopback interfaces.
See also Configuring ACLs to Loopback.
Port Channel Interfaces
Port channel interfaces support link aggregation, as described in IEEE Standard 802.3ad.
This section covers the following topics:
• Port channel definition and standards
• Port channel benefits
• Port channel implementation
• Configuration task list for port channel interfaces
Port channel definition and standards
Link aggregation is defined by IEEE 802.3ad as a method of grouping multiple physical interfaces into a
single logical interface—a Link Aggregation Group (LAG) or port channel. A LAG is “a group of links
that appear to a MAC client as if they were a single link” according to IEEE 802.3ad. In FTOS, a LAG is
referred to as a port channel interface.
A port channel provides redundancy by aggregating physical interfaces into one logical interface. If one
physical interface goes down in the port channel, another physical interface carries the traffic.
Command Syntax Command Mode Purpose
interface loopback number CONFIGURATION Enter a number as the loopback interface.
Range: 0 to 16383.