SBC and Ubiquiti EdgeRouter Pro

[DavidHodgson]

Hi All,

We have a 3CX system hosted on Microsoft Azure, all necessary ports open to the Azure VM including port 5090.

We have installed a Ubiquiti EdgeRouter Pro 8 into the network which is connected to our FTTP directly from the supplier using a Fibre Cable and Module plugged into the ER Pro. The connection is established using PPPoE.

We have an SBC installed on a Hyper-V server using the Linux Distro provided by 3CX.

The SBC will not connect to the PBX, it attempts a connection which we see in the 3CX logs but then disconnects. We have a register OK and a register fail at the same time on the SBC Trunk.

I know that port forwarding / firewall rules do not need to be in place for SBC traffic, we do not block any outbound traffic via the firewall on the ER Pro only the inbound traffic is restricted but again no port forwarding or firewall configuration needed for SBC to work.

The ER Pro is configured with a secondary 4G WAN connection provided by a router with a SIM card in it and Fail Over is configured. The ER Pro through some misconfiguration on the PPPoE failed over to the 4G connection and the SBC connected and stayed connected.

I wonder if anyone has any ideas what might be happening with the primary PPPoE connection that is preventing the SBC from connecting. It would not seem like it is the ER Pro that is the issue as it connected when on the failover WAN connection.

I've been looking at this all day and I'm pulling my hair our.

Thanks in advance.

 

[Alphabetic]

Have you checked to see if the WAN IP of the PPPoE is blacklisted on the PBX and have you tried a tracert to the PBX?

do a wireshark from the PBX to see if it can see it hitting it.

 

[DavidHodgson]

I've checked for blacklisted IP's in-fact the WAN IP where the SBC resides was whitelisted.

I'll try a tracert and wireshark.

 

[Marconi]

I have used 3CX server and SBC behind UniFi USG 3P & 4P as well as an SBC behind a UDM Pro without any problems so I doubt that it is the EdgeRouter causing issues (I could be wrong, though). One thing I did have any issue with using 3CX Debian on Hyper-V is that ntp must be installed otherwise time issues will cause you problems (See this page for instructions if you haven't already installed ntp).

Since the SBC connects when on the 4G network I suspect that there is some filtering being done by the ISP on the PPoE connection so it would be worth talking to them about it. If they are using load balancing that might cause problems and it might be worth asking for a fixed IP on the link (it might cost you a bit more). Also, ask them to turn off SIP ALG if they have it on (not that this should affect the SBC bridge connection to the 3CX server).