C H A P T E R 6 Configuring Fast Etherchannel And Gigabit Etherchannel; Etherchannel Overview; Understanding Frame Distribution; Hardware Support For Etherchannel - Cisco WS-C2948G-GE-TX Configuration Manual

PAgP and LACP

EtherChannel Overview

Fast EtherChannel and Gigabit EtherChannel port bundles let you group multiple Fast or Gigabit
Ethernet ports into a single logical transmission path between a switch and a router, a host, or another
switch. Depending on your hardware, you can form an EtherChannel with up to eight compatibly
configured Fast or Gigabit Ethernet ports on the switch. In addition, on the Catalyst 4500 series
switches, you can configure an EtherChannel using ports from multiple modules. All ports in an
EtherChannel must be the same speed.
The switch distributes frames across the ports in an EtherChannel according to the source and destination
MAC addresses. If a port within an EtherChannel fails, traffic previously carried over the failed port
switches to the remaining ports within the EtherChannel. A trap is sent when a failure identifies the
switch, the EtherChannel, and the failed link.
You can configure both Fast and Gigabit EtherChannel bundles as trunk links. After you have formed a
channel, you can configure any port in the channel as a trunk. The configuration is applied to all ports
in the channel. You can also configure identical trunk ports as an EtherChannel. For more information,
see the
"Configuring VLAN Trunks on Fast Ethernet and Gigabit Ethernet Ports."

Understanding Frame Distribution

EtherChannel distributes frames across the links in a channel based on the low-order bits of the source
and destination MAC addresses of each frame. The frame distribution method is not configurable.

Hardware Support for EtherChannel

EtherChannel support is hardware dependent. You can enter the show port capabilities command to
determine whether your hardware supports EtherChannel, and to confirm which ports you can bundle
into a single EtherChannel.
An EtherChannel bundle can consist of any two to eight ports. Ports in an EtherChannel bundle do not
have to be continuous, and they do not have to be on the same module.
Due to the port ID handling by the spanning tree feature, the maximum supported number of channels
is 126 for a 6-slot chassis.
PAgP and LACP
Port Aggregation Control Protocol (PAgP) and Link Aggregation Control Protocol (LACP) allow ports
with similar characteristics to form a channel through dynamic negotiation with adjoining switches.
PAgP is a Cisco-proprietary protocol that can be run only on Cisco switches and those switches released
by licensed vendors. LACP, which is defined in IEEE 802.3ad, allows Cisco switches to manage Ethernet
channeling with devices that conform to the 802.3ad specification.
MAC address notification settings are ignored on PAgP and LACP EtherChannel ports.
Note
To use PAgP, see the
LACP" section on page
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
6-2
"EtherChannel Configuration Guidelines and Restrictions" section on page 6-3
"Understanding PAgP" section on page
6-16.
Chapter 6 Configuring Fast EtherChannel and Gigabit EtherChannel
6-5. To use LACP, see the
and Chapter 11,
"Understanding
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