Problem 3CX Desktop App/web client with Sonicwall VPN

[RodrigoABP]

Hi,

I updated the 3CX v16 to v18 in last week, and now I verified that web client and 3CX Desktop App (new client to Windows) are crashing when the Sonicwall VPN (Global VPN Client) is connected. More specifically, when I realize a call, the VPN tunnel is break and all connections of network are down, and I need reconnect VPN to return all connections.

This situation don't occurr with 3CX Desktop legacy and don't occurred using web client and desktop app without VPN.

Do you know about a scenario how this, VPN+3CX, and how to resolve? The new client desktop was changed? Do I need allow others ports in my firewall?

Thank you.

 

[ChrisC_3CX]

When using a VPN client, you must always make sure that the VPN client has established the connection before you launch any of the 3CX Apps/Webclients. Also you must configure the VPN in a way that has all of the client's traffic routed through the VPN connection otherwise you will most definitely face issues.

 

[RodrigoABP]

When using a VPN client, you must always make sure that the VPN client has established the connection before you launch any of the 3CX Apps/Webclients. Also you must configure the VPN in a way that has all of the client's traffic routed through the VPN connection otherwise you will most definitely face issues.

Hi, thank you for response.

About the first point, the problem to occurr same establishing the VPN connection before the to launch 3CX App or web client.

About the other point, all traffic is routed through VPN, but the problem is not the degradation inf 3CX, what occurr is a total break of connection, I can't to connect nothing in network, for example, RDP to servers, SMB to mapped drivers, the VPN tunnel simply down and don't return if I not restart.

 

[ChrisC_3CX]

About the other point, all traffic is routed through VPN, but the problem is not the degradation inf 3CX, what occurr is a total break of connection, I can't to connect nothing in network, for example, RDP to servers, SMB to mapped drivers, the VPN tunnel simply down and don't return if I not restart.

So your VPN connection drops completely when placing a 3CX call? That is certainly strange, I don't remember seeing any similar reports of this so it might be worth first identifying what causes the VPN connection to drop. Is it specific traffic the 3CX client is sending? If yes, why does that effect the VPN connection in that way, does it have any limitations perhaps?

Know that the 3CX Webclient sends and receives traffic:

• HTTPS port of the PBX (default TCP 5001 or 443)
• WebRTC ports (UDP port range 10500 - 10999)

Note: The above are all destination ports. The source ports used are high random ports.

Hopefully this info helps you narrow this down.

 

[RodrigoABP]

So your VPN connection drops completely when placing a 3CX call? That is certainly strange, I don't remember seeing any similar reports of this so it might be worth first identifying what causes the VPN connection to drop. Is it specific traffic the 3CX client is sending? If yes, why does that effect the VPN connection in that way, does it have any limitations perhaps?

Know that the 3CX Webclient sends and receives traffic:

• HTTPS port of the PBX (default TCP 5001 or 443)
• WebRTC ports (UDP port range 10500 - 10999)

Note: The above are all destination ports. The source ports used are high random ports.

Hopefully this info helps you narrow this down.

Correct, I think that the VPN tunnel is overlap by 3CX, I don't know too, because don't have any log on VPN client or Wireshark...

I don't know if a possible 3cx's criptography is overlap the VPN's criptography.

An additional information that verified today: the peer VPN and 3CX webclient is published in same URL, for example, abcabc.domain.com, and I have other peer VPN in URL defdef.domain.com. If I connect VPN using second peer, 3CX don't break the VPN client, so this reforce that something in 3CX is root of problem.

 

[ChrisC_3CX]

the peer VPN and 3CX webclient is published in same URL

What do you mean they are in published in same URL? Are you somehow using the 3CX FQDN for your VPN? I'm not sure I completely understand what you mean here.

If I connect VPN using second peer, 3CX don't break the VPN client, so this reforce that something in 3CX is root of problem.

Well, to be honest, I kind of think that proves the exact opposite. First off, you already confirm 3CX works fine without a VPN connection. The fact that you also confirm 3CX to work with a different VPN connection further proves that the issue may be something with the specific VPN connection causes issues since that is the only thing you changed in these 3 different cases.

 

[RodrigoABP]

What do you mean they are in published in same URL? Are you somehow using the 3CX FQDN for your VPN? I'm not sure I completely understand what you mean here.


Well, to be honest, I kind of think that proves the exact opposite. First off, you already confirm 3CX works fine without a VPN connection. The fact that you also confirm 3CX to work with a different VPN connection further proves that the issue may be something with the specific VPN connection causes issues since that is the only thing you changed in these 3 different cases.

Hi, when I said "same URL", I wanted to say that both are published in same public IP but using different URLs, for example, 3CX is using 3cx.domain.com and VPN vpn.domain.com, both in same public IP 10.10.10.10.

And about your suggestion, I realized a test using other VPN peer and the error in 3CX don't occurred, in this test VPN peer in URL vpn2.domain.com in public IP 11.11.11.11 and 3CX in URL 3cx.domain.com in public IP 10.10.10.10.

So I need understand if really there is a incompatible to use both in same public IP or I need configure something with the change of new desktop client.

 

[ChrisC_3CX]

I don't think that having the VPN's FQDN point to the same IP as the PBX would be an issue. It is only used by the VPN client to establish the connection and should not, by itself, have an adverse effect on the 3CX Client.