EtherChannel

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. Donot configure a GigaStack gigabit interface converter (GBIC) as part of an EtherChannel.
• An interface that is already configured to be a Switched Port Analyzer (SPAN) destination port will not join an EtherChannel group until SPAN is disabled.
• Donot configure a secure port as part of an EtherChannel.
• 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 dot1q.

Configuring Layer 2 EtherChannel



Verifying EtherChannel