SIP over OpenVPN

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MMat
OpenVpn Newbie
Posts: 4
Joined: Mon Nov 19, 2012 6:10 am

SIP over OpenVPN

Post by MMat » Tue Jun 21, 2016 9:07 am

I have what seems to me an uncommon, perhaps a unique problem.

At home, I have a Debian server acting as router; it runs two distinct OpenVPN instances, a bridged and a routed one respectively.

I have installed the Android app on my cell phone, and it connects perfectly to the (routed) OpenVPN instance on the sever.

Things I checked: from the phone, I can ping LAN hosts by name (=dns resolution works), I can open ssh connections (via ConnectBot app, =tcp over udp works), I can surf the Web and services like http://www.whatismyipaddress.com correctly report my origin IP address as my home's, not my phone's (http over udp works).

However, I also have a softphone app on the cell phone (Linphone, BTW), which cannot register to my Elastix PBX in my home LAN. The softphone can easily register when it is connected via wifi to my home LAN; when on the OpenVPN, it can easily ping the PBX, and the PBX name is correctly resolved.

The weird thing is that I use tcpdump on the home router (the Debian box) to check on packets coming thru the OpenVPN and destined to the PBX, and there is none: the reason why the softphone does not register to the PBX is that the PBX (which is located on a different machine than the router) is never reached by packets from the cell phone softphone app.

I can see this way all sorts of packets originated by the cell phone and destined to my LAN, both to the PBX and to other machines (always ICMP and TCP protocols), but the SIP packets are lost somewhere before reaching my home router, even though they are encapsulated in the OpenVPN connection.

I do not have a rooted phone, so tcpdump or Wireshark will not work, and I cannot be positive that the packets are leaving the phone correctly; they do, of course, when the phone is on my home wifi, but that's all I can say.

Is there any reason why SIP packets should not jibe with the OpenVPN version for Android? Is it possible the telephone operator blocks SIP packets, though encapsulated in the OpenVPN connection, to prevent me from saving on my telephone plan (seems farfetched, given the encryption and security of OpenVPN, yet when all else fails even the impossible begins to appear possible)? Is there any extra test I can perform to try and pinpoint the root cause of the failure?

In other words: I am at my wit's end, I would welcome any suggestion.

MMat
OpenVpn Newbie
Posts: 4
Joined: Mon Nov 19, 2012 6:10 am

Re: SIP over OpenVPN

Post by MMat » Wed Jun 22, 2016 8:23 am

Bug of the Linphone Android app. A new softphone (zoiper) works flawlessly.

storage
OpenVpn Newbie
Posts: 1
Joined: Mon Mar 23, 2020 4:01 pm

Re: SIP over OpenVPN

Post by storage » Mon Mar 23, 2020 4:12 pm

I have the same problem.

I have been trying to register a softphone to the PBX that is on my local network connected to the VPN client on android, I was checking if the error was configuration but not everything is correct, however this same application on iphone works well, you can even register a softphone with the telephone exchange.

I consider this an application bug, so I recommend you check and notify me of any updates.

Somebody has the solutions??

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