Why did the traffic stopped.
Each interface on FWSM-A needs to have direct layer 2 connectivity to each corresponding interface on FWSM-B. The same also
holds for the ACE.
Additionally, the interfaces on FWSM 1 and FWSM 2, that are facing the
ACE, both need to have direct layer 2 connectivity to the corresponding
interfaces of both ACE 1 and ACE 2.
In other words trunk between the two switches should carry all vlans utilized by FWSM & ACE.
With L2 trunk available, STP will put vlan X (vlan b/w ACE & FWSM) in blocking state once FWSM-A goes down.
So if CONTEXT-A on FWSM-A goes down then incoming traffic should hit CONTEXT-A on FWSM-B first & then from there it should cross the Trunk between the switches and should hit corresponding ACE context on ACE-A.
Few questions
1. Are you trunking all data vlans (FWSM & ACE) between the two switches?
2.Are you allowing BPDUs to pass through ACE?
3. Have you disabled BPDU guard & Loop guard globally on Cat65Ks
4. If you run "show spanning tree vlan X" & "show spanning tree vlan Y" (where X & Y are vlans bridged by ACE, Do you see same Root for both vlans.
Syed Iftekhar Ahmed