Draytek 2955 - inbound not working

[amarsys]

I'm testing 3CX, and things seem pretty good, except we can't receive incoming calls.

We have a Draytek 2955 behind 2 x Draytek ADSL modems and 2 x ADSL.

I have followed the excellent instructions on the 3CX support pages for the Draytek 2820:
http://www.3cx.com/blog/voip-howto/draytek-firewall-voip/
... the 2955 menus are identical.

I have run the firewall checker, it completed successfully.

Sip trunk provider is Gradwell. They are very helpful but are not familiar with 3CX. There is just one inbound number (no DDI).

We are just using the 3CX softphone for now, and it works internally between extensions and can call outbound.

Basically outbound calls work, but with inbound calls the caller doesn't get a ring tone, the line is silent. There is no activity in the 3CX log at the time the call is made. I can see that I might not have got the inbound DDI configuration configured properly, but since there is no log activity I don't think the inbound call is getting beyond the firewall. A very nice lady at 3CX has also told me that 99% of 3CX problems are firewall problems, which I can well believe.

Any ideas what to try next?

 

[leejor]

I would try getting it to work on a single ADSL modem first, once you have that up and going, then introduce the second. If that won't work, then you will probably have to make use of Wireshark to discover why the providers packets aren't reaching 3CX. It may have something to do with STUN and two Public IP's

 

[amarsys]

That is a good idea, to try using a single ADSL line, but it didn't make any difference. Neither did enabling and disabling STUN. I downloaded wireshark but that level of debugging is beyond me! I will keep playing with the firewall, because I think it is somehow blocking the inbound (but not outbound) traffic.

 

[archie]

I saw traffic capture after some Draytek (sorry, don't know model), and I saw it incorrectly replaces IP in SDP when SIP ALG is ON. Incorrect is a content-length after change. I'm not sure if it's the case, but you can find yourself if you take wireshark capture on both sides of Draytek.

 

[amarsys]

I have now replaced the Draytek with an old Netgear FVS124G. Same result - everything else works but no outbound calls on 3CX, and no sign of any traffic reaching the 3CX server. Local Windows firewall is turned off. Starting to think there must be some other ports involved on inbound calls that I have not enabled?

 

[karl800]

Strange enough i'm having same issues but with a speedtouch router, all was ok, then had to have amove round of servers, so switched them all off then back on, now i cant dial in. i get one ring tone, then automated voice message to answer phone.

Not sure whats happening.

 

[leejor]

I have now replaced the Draytek with an old Netgear FVS124G. Same result - everything else works but no outbound calls on 3CX, and no sign of any traffic reaching the 3CX server.

The most important port, the one to concentrate on first, is 5060 (if you've left that port as the 3CX default). That is the port that you send to your VoIP provider during registration letting them know how to "contact" you. The other ports become involved for audio once a call is established. For now I would work on getting that port to pass through your router so that a call attempt shows up in the logs.

If all else fails, try running the 3CX PC direct on your modem, picking up a public IP. See if that solves the problem, but don't leave it that way. If it does work for incoming, then you can be certain that the router is somehow blocking port 5060 from getting through.

You may have to disable STUN during the test.

 

[complex1]

After replacing the 2955, do you have also problems with outbound calls? Or do you mean inbound calls.
What kind of Draytek ADSL modems are you using? Is the problem not caused by these ones instead of the 2955?
I am using a 2930 without any problems.
Have you checked if SIP_ALG is switched OFF as Archie proposed?
Login the router by using Telnet, type your password and then type “sys sip_alg ?” <enter>
“current SIP ALG is disabled” should now be read.

 

[amarsys]

Sorry, my previous post was muddled - the only problem I have is with incoming calls - the caller just hears a silent line and there is no activity on the 3CX log. Outbound calls have always worked.

I have checked the SIP_ALG and it was indeed disabled on the Draytek 2955 so I left it like that. The Netgear FVS124G had an option to control this though its settings, but it made no difference either way.

The modems are Draytek Vigor 120s. I have two of them, one for each line. They seem very good, and are true modems. When I switched to the FVS124G, I deliberately only configured it for one line and left out all our usual VPN and other stuff, so it was the simplest possible setup.

It is useful to know that a 2930 works. That, along with the fact that I found no difference when using the Netgear suggests the problem is somewhere else in the chain.

Thanks for the suggestion to focus on 5060, I will do that next. I can't actually put the 3CX machine on the modem because it is running in a VM on our HyperV server. I have enabled and disabled the Windows firewall, that seems to make no difference (and 3CX itself seems to have created several rules in the firewall during installation).

It is starting to look like the problem could be with our SIP trunk (although it works outbound) or our ISP.

 

[complex1]

I still think the problem is caused by the Vigor120, because the Vigor120 has firewall facilities as NAT, SPI, DoS and IP Packet filtering. http://www.draytek.com/user/PdInfoDetail.php?Id=71#PdSk

The 2955 (and FVS124G) has also firewall facilities and two such devices in a row is asking for trouble.

It should be possible to configure the Vigor120 as a bridge. So, if you can manage this, the firewall etc. will be disabled (I think) and all traffic will be pass through to the 2955.

 

[amarsys]

I logged in to the Vigor 120. I'm in the UK, and the UK models seem to be pre-configured and restricted to act purely as ADSL modems, converting the ADSL to Ethernet. The "PPoE pass through for wired line" is checked and cannot be un-checked. Most of the configuration pages in the US manual don't exist in the UK manual (the latter is only 8 pages). The ISP login settings are entered in the Draytek 2955, not in the 120s.

 

[complex1]

It is starting to look like the problem could be with our SIP trunk (although it works outbound) or our ISP.

I think you are right.

Please, give some feedback if you know more

 

[amarsys]

I have switched the trunk to my other ADSL, which is from a different ISP. Outbound calls still work, inbound still not working. So it is probably not the ISP, so it must be the SIP trunk. I have placed a support call with the provider (Gradwell).

 

[leejor]

Let us know what the outcome is. I'm curious if they are, in fact, trying to send the call set-up on port 5060 or another.

 

[amarsys]

Well this is embarassing. It seems that in all the messing around I didn't configure all the incoming IP address details on Gradwell's control panel, so they were trying to connect to another address. In my defence, I had in fact configured the trunk itself, but there is a separate page to change the IP address for the phone number, which is not obvious.

For anyone else coming to this thread, the encouraging news is that 3CX does work through a Draytek firewall with a Gradwell SIP trunk. Hopefully that is useful to know because if you are just dipping your toes in the VoIP waters then Gradwell plus the free version of 3CX is probably the cheapest way to do it in the UK as Gradwell don't oblige you to take 10 x DDI numbers etc. The down-side is that Gradwell don't really provide any assistance for 3CX users.

Hopefully this will be of help to anyone else following this path.

 

[realtonetech]

please try to open the DMZ funcuton on ADSL router, and point DMZ host as 3CX's IP address, i think this is NAT probelm, your router with very short expire;

You can check 3CX's LOG to verify, if 3CX recieved INVITE message from SIP server;

 

[amarsys]

Thanks for the suggestion, however we have got it working (sort of) with just the ports specified in the 3CX documentation, the main problem was a configuration mistake by me with the SIP trunk provider.