Phone drop-offs with Netgear Nighthawk X4S D7800

[ccomley]

We have a client who set up his own LAN with a Netgear router. We've not used the router but we checked that the SIPALG could be disabled and went ahead implementing three Remote(STUN) extensions at his location.

He actually tested the phones at a different location, with a different router, the Netgear was brand new and bought to go in an office he moved in to a few days later. Once in the new office, the phones kept losing registration, usually right after a call, and would not reconnect without being rebooted. BLFs were never up to date, and, all in all, it was a nightmare.

Soft-client remained connected so whatever the problem was was not triggered with the tunneled connection.

We subsequently replaced the Netgear with a Draytek Vigor and since then everything has gone smoothly. So there's no doubt - the Netgear was causing the problem.

Does anyone have any idea what the specific problem is, and, if it's possible to fix it by updating some setting i the router? I'm speculating a too-short time-out setting on UDP connections, possible in the NAT department, but this is just where I'd start looking based on the symptoms if I had access to the router, which I don't.

If we can't work out if the problem is solvable, I'll have to add the router to the blacklist - which so far ONLY contains devices where the SIP ALG can't be disabled.

 

[lneblett]

You did not mention the phone make/model nor how many phones are behind the NAT. The best I can suggest at the moment is to insure that the phones have keep-alives enabled with a time period of no more than 30 seconds. That a NAT IP in entered into the phones so that when sending messages that the connect and SDP info always reflects the public IP of the remote site. You should use a different local SIP port on each phone as well as a different RTP range on each. This should help the router keep the NAT/PAT tables straight as otherwise it may be an issue that the router is not able to keep the routing straight if all phones are using the same ports.

Some routers are better at maintaining the NAT/PAT than others when you have multiple devices behind a NAT and nothing implicitly set (no port forwarding). You may also need to consider an SBC or even a VPN between sites.

 

[ccomley]

Thanks. Yealink T42S, configured by 3CX (up toddate f/ware and templates, v15sp2)
I did say - three phones!

In this case replacing the router with a Draytek has solved the problem, and the customer was happy to do it. (And we normally use Zyxel or Drayteks anyway - *he* chose the Netgear! ) So I was more wondering if anyone knew if it was possible to get the Netgear to play nicer, without having to take special measures on the phones/3cx side.

 

[lneblett]

Sorry, I see the 3 now.
I have a client using a Nighthawk with 6 phones behind it. They are not using 3CX, but a hosted service as they are an insurance agency and the hosted service has a deal with HQ. In any event, they have no issues, but are configured as I outlined earlier. They are using GS2140 phones and initially had much the same issues until we made the changes.

 

[apostolis_3CX]

Hi ccomley,

To add to what Ineblett mentioned above regarding SIP and RTP ports used for remote extensions, kindly notice that each Remote STUN Extension must have a unique Local SIP Port and Unique RTP Port range.
In the provisioning tab of each extension make sure that the Local SIP Port of Phone is different between the extensions that you have selected to register through STUN method and are behind the same Public ip address (1st 5065, 2nd 5066, 3rd 5067, etc.. ) as well the Local RTP Audio Ports Start ( 1st14000-140011, 2nd 14012-14023, 3rd 14024-14035, etc.. )

Make sure that since each phone has dedicated ports, on the remote firewall you have to make a Static NAT and Static Port Forwarding to the Private ip address of each phone. If you are using Yealink phones and these are on firmware x.80.x.x then you will need 12 RTP ports for each extension.

1) In the Management Console each Remote STUN Extensions must have a unique Local SIP Port and Unique RTP Port range and the RTP Port range must be 10 ports (for Yealink phones 12 ports) per remote site. This means that if we only had Yealink phones that would be e.g.:

- Ext A should have Local SIP Port: 5065 and RTP Port Range: 14000-14011 (12 ports)
- Ext B should have Local SIP Port: 5066 and RTP Port Range: 14012-14023 (12 ports)
- Ext C should have Local SIP Port: 5067 and RTP Port Range: 14024-14035 (12 ports)
- etc...

2) Once you have done this, then on the Remote Location Router/Firewall behind which the phones are residing, you must:

- Disable SIP ALG or any similar port remapping feature.
- Create NAT/Port Forwarding Rules so that, as per the above example:
--- Ports 5065 TCP/UDP and 14000-14011 UDP are forwarded to the IP of Ext A
--- Ports 5066 TCP/UDP and 14012-14023 UDP are forwarded to the IP of Ext B
--- Ports 5067 TCP/UDP and 14024-14035 UDP are forwarded to the IP of Ext C
--- etc...

- This also implies that the the phones/endpoints should have Static LAN IPs assigned to them.