LACP LAG that won't come up

Hi Raffs

At least they need to be the same LACP mode.

Can you share interface config from both sides?

Which one did you choose? FGT always expects LACP.
sw0(config-if)#channel-group 1 mode ?
  on                              Add port without LACP
  auto                           Add port with LACP

Toshi

Hopefully, this article will help you in debugging:

https://community.fortinet.com/t5/FortiGate/Technical-Tip-Initial-troubleshooting-steps-for-LACP-Link/ta-p/198339

In fact, a default LAG port starts out with default settings suitable for Cisco switches, that is, BPDUs are exchanged every 30 seconds (meaning, a link down will take 29 seconds at maximum to be detected). This is "lacp-mode slow".

I would look into the distribution algorithm (by MAC, by source IP, dest IP,...) to be matching on both sides.

For debugging, the "diag netlink aggregate name <bla>" command is helpful. The flags displayed of both ends of the link should be identical, and signal the link is working.

All of this applies of course only if the information given is correct. No FGT cluster or switch stack involved, no intermediates etc. etc. Unfortunately, many posts on the forum start out describing a simple setup which later is revealed as being 2 orders of magnitude more complicated. We all cannot use our crystal balls over long distance...

hi,

can you remove the config and reconfigure again from scratch?

i'd suggest to shutdown first the member ports on the cisco switch, configure LACP using mode "active" then unshut.