Connectivity drops if one physical chassis in a stack is down.

[as_iceconnect]

We have 2xOS6900 in a virtual chassis. Both are connected via 10Gb uplink to ports on the firewall which are in an active-passive LAG.
Scenario 1:
Chassis 1 uplink port disabled
Chassis 2 uplink port enabled
We can ping the firewall

Scenario 2:
Chassis 1 uplink port enabled
Chassis 2 uplink port disabled
We can't ping the firewall

Everything works fine so long as the uplink is using Chassis 2. From what I can tell, the configs across both chassis is the same. Any ideas what could be causing this?

[silvio]

some month ago we had a similar issue in a VC 6860 8.7.280.R01 . ALE support has found out the reason - with update of the VC it was solved.
now you can check the mac-learning.
BR Silvio

[as_iceconnect]

Hi Silvio. Thanks for the response. I'll raise this with ALE support and see what they suggest. Looks like we might be on an older firmware but it's an infrastructure we've inherited so still trying to wrap my head around the setup.