Hi all,

I've got an odd VOIP registration issue which I've seen on Vigor 2865's, 2860's and 2832's.

I can use SIP/Mobex/VOIP through a 4G dongle if plugged into the USB of a PC, so the service allows it.
I can also use the same if connected to the Draytek which has Internet via a WAN2 Ethernet connection (Virgin Media in modem mode to Draytek WAN2), so the Draytek allows this for WAN1 ADSL/VDSL and WAN2 Ethernet connections.

For some reason, even though the same 4G dongle works for load balancing data in the Draytek, so PC's work fine with it, it won't allow SIP phones to complete registration, so VOIP phones wont work when on 4G via the Draytek.

The routers all have the latest firmware, but something on the WAN5 USB setup blocks VOIP, where the WAN1 and WAN2 allow it.

Any ideas please? I know other people who use 4G Dongles via other routers with no issues, it's just these Draytek's which seem to block VOIP via 4G on USB but not on WAN2 or WAN1 connections.

Any ideas please? :idea:

Hi Marcus,

Not an answer as such, but I am currently looking into 4G connectivity as a back up as well. So I am really reaching out to say keep me/this forum posted.

Like you I already have a 4g back, via USB, working and the router successfully fails over to 4g when the primary line fails.

Like you though I also run a VoIP service and it is yet untested in back up mode (time constraint). However, I do know my SIP PBX registers using my primary IP to talk to my VoIP provider. When you switch over to the 4g backup, clearly your routers IP address changes. To overcome this I have registered a DDNS host address in place of my actual IP and after allowing a few minutes for everything to update, I fully expect this to work.

However, if it does not, then it looks like it may be a double NAT problem because there are two routers now involved in routing your traffic (your 4g modem then your Draytek). This won't be difficult to resolve, so let me know how you get on, I just haven't found a solution to it yet

Hi, I set my routers up so the VOIP phones always use the same local IPV4 address and this range of IP's only uses WAN1 or 2 (whether at ADSL or WAN Ethernet sites) for Internet. If I allow them to use USB 4G on WAN5, they fail to register. The registration request is received at the host, but the response does not get back to the phones or softphone Laptop.

It's not just because the IP changes during switch over as I use load balancing. Even on 4G only, VOIP will not register at all via USB 4G, even though the same 4G dongle in a laptop registers SIP services fine.

With regards to the double NAT issue, you may have a point. I'm going to play round trying to get it to work on PPP mode, not DHCP.
The thing is though, the PC's all work fine even with the double NAT issue, it's just SIP/VOIP. If I use softphone software on my laptop, it only works if the Internet goes via a connection other than USB 4G. Other data services are fine though.

My VOIP host uses these to provide routers with Internet when out at shows, so it's possible somehow.
They don't seem to think anything special needs setting up.

This I suspect will become a large issue for Draytek users when PSTN phones are switched off in a year or two.

Cool, Looks like you are using your phones to register with an external PBX, whereas I have an internal PBX and the phones register to that, so it sounds like our installations are a little different.

I will follow progress with interest.

I think I've cracked it.

Under NAT, enable ALG. I ticked to enable SIP on the suggested port of 5060 for both UDP and TCP.
Now even without WAN2 plugged in, so 4G USB only providing Internet, all 13 phones eventually registered and can make and receive calls.

That's a bonus, we can now have fault tolerance on VOIP as well as data for all customers I sell VOIP to.
The only thing which could be an issue is my host appeared to blacklist my WAN IP for data when I first enabled it, but it seems fine now.

Thank you. I won't be able to do any testing now until next week but I shall keep this in mind...