40-12
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 40 Configuring EtherChannels and Link-State Tracking
Configuring EtherChannels
EtherChannel Configuration Guidelines
If improperly configured, some EtherChannel ports are automatically disabled to avoid network loops
and other problems. Follow these guidelines to avoid configuration problems:
• Do not try to configure more than 48 EtherChannels on the switch or switch stack.
• Configure a PAgP EtherChannel with up to eight Ethernet ports of the same type.
• Configure a LACP EtherChannel with up to16 Ethernet ports of the same type. Up to eight ports can
be active, and up to eight ports can be in standby mode.
• Configure all ports in an EtherChannel to operate at the same speeds and duplex modes.
• Enable all ports in an EtherChannel. A port in an EtherChannel that is disabled by using the
shutdown interface configuration command is treated as a link failure, and its traffic is transferred
to one of the remaining ports in the EtherChannel.
• When a group is first created, all ports follow the parameters set for the first port to be added to the
group. If you change the configuration of one of these parameters, you must also make the changes
to all ports in the group:
–
Allowed-VLAN list
–
Spanning-tree path cost for each VLAN
–
Spanning-tree port priority for each VLAN
–
Spanning-tree Port Fast setting
• Do not configure a port to be a member of more than one EtherChannel group.
• Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running
PAgP and LACP can coexist on the same switch or on different switches in the stack. Individual
EtherChannel groups can run either PAgP or LACP, but they cannot interoperate.
• Do not configure a Switched Port Analyzer (SPAN) destination port as part of an EtherChannel.
• Do not configure a secure port as part of an EtherChannel or the reverse.
• Do not configure a private-VLAN port as part of an EtherChannel.
• Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an
IEEE 802.1x port. If you try to enable IEEE 802.1x on an EtherChannel port, an error message
appears, and IEEE 802.1x is not enabled.
• If EtherChannels are configured on switch interfaces, remove the EtherChannel configuration from
the interfaces before globally enabling IEEE 802.1x on a switch by using the dot1x
system-auth-control global configuration command.
• For Layer 2 EtherChannels:
–
Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with
different native VLANs cannot form an EtherChannel.
–
If you configure an EtherChannel from trunk ports, verify that the trunking mode (ISL or
IEEE 802.1Q) is the same on all the trunks. Inconsistent trunk modes on EtherChannel ports can
have unexpected results.
–
An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking
Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an
EtherChannel even when PAgP is set to the auto or desirable mode.