Solved 3CX causes router to drop Internet connection

[jonathanc]

Please can someone help me with a problem that's driving me absolutely nuts?

Randomly, both incoming and outgoing calls cause my Draytek Vigor 2925n router to drop its Internet connection. When I'm not using VoIP the connection is extremely stable.

One unusual thing about my configuration is that it uses wide-area WiFi, so that my network is subnetted from the router connected to the local mast - ie my WAN IP is 192.168.10.10 and my LAN uses 192.168.1.x (I hope I've got the right terminology). I can't have a static public IP address.

I can't figure out what's going wrong, even after spending months working through reams of logs (which I won't upload because I'm not sure what would be useful). The only clue is that if I make a call from each of my 4 SIP trunks in turn, the third call fails, taking the Internet connection with it; but sometimes just making or receiving one call causes the connection to fail.

I appreciate that this information is scanty, but I just wonder if anyone recognises these symptoms. If so, I'd be so very grateful for a pointer!

3CX Activated Standard 15.5.3849.1 on 64-bit Windows 10 Home (2017).

Many thanks in hope

jonathanc

 

[sip.bg]

3CX should not influence the internet connection in any way.

The network configuration you have is double NAT, once your LAN 192.168.1.0/24 is NAT-ted to 192.168.10.10 and then this network is NAT-ted to real public IP. I suppose you can't control the outer router, which means your configuration should not be supported, or at least will not work with VoIP providers and external extensions. What is saying 3CX firewall checker ? What address you have defined as public IP for the PBX (the FQDN should resolve to it)?

I guess the reason for blocking internet is either an address conflict, some of the routers reset connections or even reboots, or at least you may have conflict on port 5060 (some routers have built-in voice ports, which utilize port 5060 and need to be disabled in order to use VoIP PBX behind the router).

Hint: Try to edit LOCALSUBNETS parameter and leave 192.168.1.0/24 as local subnet (replace 192.168.0.0/16 value). Restart 3CX services. This could help.

I'm afraid you have to eliminate the inner router and to install your PBX in 192.168.10.0/24 network with phones in the same network or eventually in 192.168.1.0/24 network, behind NAT. Thus the PBX will not be double NAT-ted. The other option is to have 2 LAN cards, one (main) in 192.168.10.0/24 network and second (for phones) in 192.168.1.0/24, if no other solution.

 

[Sopock]

VoIP for cost-effective communication port is present only on models like Vac and Vn-plus

Spoiler: Flexibility Internet Application

SIP ALG (Application Layer Gateway) is a feature which is enabled by default in most DrayTek Vigor routers and inspects VoIP traffic as it passes through and modifies the messages on-the-fly.

 

[leejor]

Unfortunately your set-up doesn't allow you to do any port forwarding, as you have no control between the public IP and the private IP assigned by your provider, which could cause some problems. On top of that, as mentioned, you are doing "double NAT".

I've seen this sort of set-up before, in southern California using Craig (which I believe is no longer in business). At the time I just insisted that they provide a public IP, and they did. In your case, that option may not be possible.

You might contact the provider and see if they can tell you what they see at their end when it does drop. Is it the wireless device, the first router, or the second? Do you own (or are able to change settings on) the routers at your end? if so, you might try swapping out with another model. It may be that a re-boot is being caused by some sort of memory, or other "overload".

 

[Sopock]

Maybe this can possibly lead to some conclusions?

Spoiler: 3G/4G/LTE Connection

Ubuntu causes router to crash

 

[jonathanc]

Many thanks, everyone, for those suggestions.

I put sip.bg's idea to my ISP, who said 'Double NAT-ted? Rubbish! You're QUADRUPLE-NAT-ted!' Their engineers are coming round on Thursday to point me to a different wide-area WiFi mast and reconfigure my system. So thank you, sip.bg, for your astute diagnosis. Hopefully, this will solve the problem - even if I have to lock the engineer in the room until it's fixed.

And thank you, too, leejor, for your suggestions: I did try a different router - a TP-link WR841N flashed with DD-WRT, but the same problem occurred. If changing the mast (and therefore the external routing) doesn't fix things, I'll make sure the ISP's engineer follows it through and gets a base-end view.

Final thanks to Sopock. I did try a 3G modem as a failover some years back, but the signal in this rural area was too poor. It has improved, but there's still no sign of 4G. Still, worth a try if Thursday comes to nothing.

Thank you once again, all, for your help. Wish me luck on Thursday!

 

[DSXVOICE]

Jonathan, you're probably on the right track - but there is a remote chance this is caused by port 25 activity. 3cx is usually configured to use port 25 to send email alerts. There are some ISP's who have an automated shut response to a high level of outbound traffic on port 25 on residential connections, as it is a sign that a bot has infected a workstation. You can test by turning off alerts for a while.

 

[jonathanc]

Many thanks, DSXDATA - I've just tried disabling notifications, but it makes no difference. Nice try, but . . .

I think it's wait-for-the-engineer-on-Thursday time!

 

[jonathanc]

It does indeed seem to have been a NATting issue. At least, changing over to the new ISP has meant that the system has been unconditionally stable for the last week.

So this one is SOLVED - with a little help from my friends!

Again, many thanks.

 

[apostolis_3CX]

I'm glad to see that your issue was resolved