PAgP

auto + auto = no EtherChannel

desirable + auto = EtherChannel

desirable + desirable = EtherChannel

The channel-group member has to match for member interfaces on the same switch.

However, it doesn't have to match the channel-group number on the other switch.

(channel-group 1 on ASW1 can form an EtherChannel with channel-group 2 on DSW1).

SW(config-id)# channel-group <number> mode <mode>