Hello. Although it does not make much sense, in some scnearis it's necessary to configure LACP (802.3ad) with a single port.

In all our private interconections with Google, they have configured 802.3ad even when a single port is used. If you don't answer to LACPDUs frames, they won't start sending traffic. In SwOS it works fine, but in RouterOS it can't be configured. We have to create a new bonding with desired port plus a unused port and it works, but we're losing a port... It can also be acheived by using a port and a "dummy" VLAN, but it's a bit sloppy...

Regards