VOIP over VPN Issues

RouterOS General
1

Hi guys,

I’m having some difficulty with the following setup:

Main Site :
1 x a2billing server which is the main voip gateway in and outbound. (10.11.200.2)
1 x Mikrotik RB750 (10.11.27.200)

VPN Site :
1 x asterisk server connecting over PPTP to the Main Site’s Mikrotik directly. (10.11.202.115 as a VPN IP at the Main Site)

Basically what i’m doing is when a call is incoming from the Main Site’s gateway, it gets routed to 10.11.27.200 and from there the Mikrotik translates it to 10.11.202.115. (This happened by itself, i didn’t add any rules).

On both PBX’s I can see the call going through however it gets drop because of some port issue. It can open the data channel but not the voice channel.

I am thinking perhaps I need to add something to the Mikrotik in NAT to point that 10.11.27.200 on ports 5060 & 10000-20000 should be forwarded to 10.11.202.115, but for the life of me I can’t wrap my head around this (or implement it for that matter with my tiny brain).

The crux is that from the VPN Site i can easily ping 10.11.200.2 but from the Main Site obviously when pinging 10.11.27.200 it pings the mikrotik and not the VPN Site’s box…

Also, no matter what type of registration I do on the SIP trunks the Main Site always sees the VPN Site’s IP as 10.11.27.200.

Any suggestions from any brainy people out there?

Thank you
Will

2

It is much easier to use IAX connections between the Asterisk boxes because all Control and Audio are sent over the same port/connection.

Do you have MT on both sides of the VPN or are you using VPN Client on the Remote PBX to connect to the RB750? If yes, I have never done that but I have setup multiple sites, each behind RB493AH with a MT<–>MT PPTP connection and this works flawlessly.

Can you detail the network configuration a bit more and post your IP->Route tables and IP->Firewall->NAT rules and IP->Firewall->Filter rules for further investigation.