I have a network setup that the topology is like this:
Fritz!Box 7590 > USG-3P > Mikrotik Router
The Fritz!Box is on the local network 192.168.1.0/24. The USG-3P is connected to the Fritz!Box through the WAN port using DHCP. After that the USG gives addresses on the range of 192.168.88.0/24 from the LAN port. On the LAN port there is a Mikrotik router that basically works on the range of 192.168.88.0/24 and every device that I connect on it gets address from that range. What I am trying to do is connect a UCM6202 and a DP752 (assigned on it are 3 DECT phones) on the Mikrotik and make it work from there. Let me clarify a few things: The Fritz!Box has the telephony lines from my ISP and I have created two VOIP trunks on the UCM6202 to make it work on the PBX. When the UCM, DP752 and the Fritz!Box are on the same subnet everything works flawlessly. But when the UCM & DP752 are on the 192.168.88.0 subnet I get no signalling when I call, no audio on outgoing calls and no incoming calls.
I am really sorry if this is a very elementary/simple question but I am very new to these things, I have spent countless hours to figure out what is going. I also tried to do port forwarding on the USG with no luck (I do not know if I did it correctly however).
Every help is much appreciated!
Thank you for taking the time to read my post.
EDIT: I have disabled ALG on the USG using config.preperties file.