We have a system with multiple VLANs and multiple controllers (AC864).
It is communication (MMS) between the controllers.
A special controller can communicate with other controllers on the same VLAN but when it is to communicate with controllers on another VLAN it does not work.
When communicating between VLANs, traffic is routed over a firewall.
Two controllers work well and can communicate within and to another VLAN but not the third.
All of this worked perfectly before upgrading the IP address on the firewall and no change occurred in configuration on the controllers or on the firewall (except for an IP address change)