Hello,
I have the following Setup:
Internet → FritzBox → Mirkotik → Different VLans with devices
In my Setup i use the fritzbox is as an Voip telephone Center. I have several voip phones within my Network. These phones are nearly all directly connected to the fritzbox at the moment.
Now i want to have one voip telephone in an vlan behind the mikrotik router. The phone rings, but i can’t hear anything. I have tried nearly all combinations of Firewall and NAT rules. But it doesn’t work. 
The phone in the vlan behind the Mikrotik router should call a phone directly connected to the fritzbox and vise versa.
I think the Problem belongs to the different UDP packets. The Systems can’t match them together.
Can anybody help and give me the NAT and Firewall rules?
The IP of the phone in the vlan is 192.168.30.252 (interface 6)
The fritzbox has 192.168.10.1 (interface 3 Mikrotik) and the Interface of the router to the fritzbox has 192.168.10.43. The phones connected to the fritzbox have also 192.168.10.x
The fritzbox Needs (in my opinion) the UDP ports 5060 and 7078-7097
Many thanks in Advance.