I'm just wondering if there is any good use of the 'passive' mode for LACP (802.3ad) link aggregation / etherchannel? I understand the recommended setup is to use active on both side so why no just get rid of the 'passive' mode all together to simplify things?
it is a matter of control with passive mode you can decide which side starts the LACP negotiation.
When both sides are active, both are allowed to start the LACP negotiation phase.
I agree that it is common practice to have active/active, but the standard provides also the passive mode for those corner cases where the bundle should be formed but you want to control which side starts the negotiation.