Port Aggregation Protocol - Cisco Catalyst 3750-E Software Configuration Manual

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Configuring EtherChannels and Link-State Tracking

After you configure an EtherChannel, configuration changes applied to the port-channel interface apply

to all the physical ports assigned to the port-channel interface. Configuration changes applied to the

physical port affect only the port where you apply the configuration. To change the parameters of all

ports in an EtherChannel, apply configuration commands to the port-channel interface, for example,

spanning-tree commands or commands to configure a Layer 2 EtherChannel as a trunk.

Port Aggregation Protocol

The Port Aggregation Protocol (PAgP) is a Cisco-proprietary protocol that can be run only on Cisco

switches and on those switches licensed by vendors to support PAgP. PAgP facilitates the automatic

creation of EtherChannels by exchanging PAgP packets between Ethernet ports. You can use PAgP only

in single-switch EtherChannel configurations; PAgP cannot be enabled on cross-stack EtherChannels.

For more information, see the

By using PAgP, the switch or switch stack learns the identity of partners capable of supporting PAgP and

the capabilities of each port. It then dynamically groups similarly configured ports (on a single switch

in the stack) into a single logical link (channel or aggregate port). Similarly configured ports are grouped

based on hardware, administrative, and port parameter constraints. For example, PAgP groups the ports

with the same speed, duplex mode, native VLAN, VLAN range, and trunking status and type. After

grouping the links into an EtherChannel, PAgP adds the group to the spanning tree as a single switch

Relationship of Physical Ports, Logical Port Channels, and Channel Groups

port-channel

Channel-group

"EtherChannel Configuration Guidelines" section on page

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

Physical ports

Understanding EtherChannels

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