Caveats to Etherchannel mode "on"

[wgarcia]

We run our etherchannels between 65xx platforms in "on" mode. This way we don't have to police the allowed VLANS on the trunks and can make VLAN allowed additions/deletions with the trunk and EC staying up. But I've heard that there is a downside to running etherchannel in "on" mode having to do with potential STP loops? Would like to know the detailed explanation. TIA.

William

[nunoscosta]

Spanning Tree Protocol sees an EtherChannel as a single port. This presents a danger of creating forwarding loops if channeling ports are not consistent on both sides of the channel. Cisco has developed a special mechanism to detect and disable channel inconsistency to prevent packet duplication, looping, and other issues associated with inconsistent EtherChannels.

Check this URL:

http://www.cisco.com/warp/public/473/127.html