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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 21 Configuring EtherChannel
Configuring EtherChannel
Note
The Catalyst 3550 supports address learning only on aggregate ports even though the physical-port
keyword is provided in the CLI. The pagp learn-method command and the pagp port-priority
command have no effect on the switch hardware, but they are required for PAgP interoperability with
devices that only support address learning by physical ports, such as the Catalyst 1900 switch.
When the link partner to the Catalyst 3550 switch is a physical learner, we recommend that you
configure the switch as a physical-port learner by using the pagp learn-method physical-port
interface configuration command and to set the load-distribution method based on the source MAC
address by using the port-channel load-balance src-mac global configuration command. Use the
pagp learn-method command only in this situation.
Beginning in privileged EXEC mode, follow these steps to configure your switch as a PAgP
physical-port learner and to adjust the priority so that the same port in the bundle is selected for sending
packets:
To return the priority to its default setting, use the no pagp port-priority interface configuration
command. To return the learning method to its default setting, use the no pagp learn-method interface
configuration command.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface interface-id
Enter interface configuration mode, and specify the interface for
transmission.
Step 3
pagp learn-method physical-port
Select the PAgP learning method.
By default, aggregation-port learning is selected, which means
the switch sends packets to the source by using any of the
interfaces in the EtherChannel. With aggregate-port learning, it
is not important on which physical port the packet arrives.
Select physical-port to connect with another switch that is a
physical learner. Make sure to configure the port-channel
load-balance global configuration command to src-mac as
described in the
“Configuring EtherChannel Load Balancing”
section on page 21-13
.
The learning method must be configured the same at both ends
of the link.
Step 4
pagp port-priority priority
Assign a priority so that the selected interface is chosen for
packet transmission.
For priority, the range is 0 to 255. The default is 128. The higher
the priority, the more likely that the interface will be used for
PAgP transmission.
Step 5
end
Return to privileged EXEC mode.
Step 6
show running-config
or
show pagp channel-group-number internal
Verify your entries.
Step 7
copy running-config startup-config
(Optional) Save your entries in the configuration file.
