EtherChannel Overview

EtherChannel provides fault-tolerant, high-speed links between switches, routers, and servers. An EtherChannel consists of individual Fast Ethernet or Gigabit Ethernet links bundled into a single logical link. If a link within an EtherChannel fails, traffic previously carried over that failed link changes to the remaining links within the EtherChannel.

    Interface Modes in EtherChannel

Guidelines for Configuring EtherChannel

• PAgP is Cisco proprietary.
• LACP is defined in 802.3ad.
• You can combine from two to eight parallel links.
• All ports must be identical:

• Same speed and duplex
• Cannot mix Fast Ethernet and Gigabit Ethernet 
• Cannot mix PAgP and LACP 
• Must all be VLAN trunk or nontrunk operational status

      ▪  All links must be either Layer 2 or Layer 3 in a single channel group.

      ▪  To create a channel in PAgP, sides must be set to:

               ▪  Auto-Desirable

               ▪  Desirable-Desirable

     ▪  To create a channel in LACP, sides must be set to:

               ▪  Active-Active

               ▪  Active-Passive

     ▪  To create a channel without using PAgP or LACP, sides must be set to On-On.

     ▪  Do not configure a GigaStack gigabit interface converter (GBIC) as part of an EtherChannel.

     ▪  Do not configure a secure port as part of an EtherChannel.

     ▪  An interface that is already configured to be a Switched Port Analyzer destination port will not           join an EtherChannel group until SPAN is disabled.

    ▪  Interfaces with different native VLANs cannot form an EtherChannel.

    ▪  When using trunk links, ensure all trunks are in the same mode—Inter-Switch Link (ISL) or   or           dot1q.