Configuring etherchannel on Cisco switches

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Configuring etherchannel on 2950+ switches with latest IOS

To configure etherchannel on 2950+ switches with latest IOS:

1. Go to `config t' mode.
2. Use `interface range Fastethernet 0/21 - 24' type command to configure group of interfaces
3. Use exact same configuration for all interfaces.
4. Use 'channel-group 1 mode desirable' to make interfaces member of channel-group 1
5. In `config t' use `port-channel load-balance dst-mac' to load-balance based on dst-mac address
6. Use command `show spanning-tree active' and you should see only one port belonging to port-channel in list of ports
7. Use command `show etherchannel 1 summary' to see that things are fine.
8. Use command `show interface port-channel 1' to see overall channel statistics and members

Give similar commands on other end to finish formation of etherchannel.

Note that etherchannel will form only when:

1. Both ends are in mode on (no PAgP)
2. Both ends are in mode desirable
3. One end in mode auto and other in mode desirable

Don't configure interface port-channel 1

There is no need to configure interface port-channel by using commands like

switchport mode trunk
switchport trunk allowed vlan 1,10,20

The port-channel interface will automatically get configured same as the members of the channel group. Also if we delete the port-channel while ports are still part of the channel then all the ports will automatically get configured in 'shutdown' mode. So if we want to remove port-channel first we should do something like `no channel-group 1 mode desirable' on all member ports before use `no port-channel 1'.

Configuring etherchannel on switches older than 2950

Upgrade switch to latest IOS so that you can get updated commands as possible.

For switches older than 2950

1. You will have to configure interfaces one by one as there is no interface range command.
2. For each interface use `port group 1' command to make interface member of port group 1
3. You can not configure load balancing. May be there is some in-built default.
4. Use command `show spanning-tree brief' as the command `show spanning-tree active' is not present.
5. Use command `show etherchannel summary' to see that etherchannel is working fine.
6. Use command `show port group 1' as command `show etherchannel' is not present.

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