I have a Draytek 2820vn with latest firmware 3.3.1 and even without any open ports, port mapping etc I can flawlessy use a software VOIP phone on my PC.

However, I have bought a Siemens Gigaset S685IP dect phone which allows landline and VOIP calls on the one handset. Using the various settings provided by BT for their VOIP line I have configured the S685IP and can make and receive calls. Unfortunately whilst the softphone works for any length of time, the S685 calls drop (on incoming and outgoing calls) after 30-120 seconds with an error message of 701.

Now why I am posting here you ask? Well good question and all things being equal I wouldn't think the router is causing the problem. My only doubt about this thought is that when I was using an earlier firmware the calls dropped after about 45 seconds and after upgrading to 3.3.1 the calls are stable for up to 2 mins. I was wondering therefore whether there is some setting on the router buried deep in the web configurator that could be causing the problem.

Another reason why I think the router could be the problem is that an old router (2600g) needed a setting telnetted to it in order to allow the softphone to work - perhaps there is something like that going on here.

I have not ruled out the possibility that BT will only lets either its hardware (ie home hub) or software (ie BT Office Communicator) work with its servers. Unfortunately I do not have access to any other VOIP lines to check this out. Perhaps if anyone can advise whether they have got any non-BT equipment to work with BT BBV that would be helpful.

Any assistance would be greatly appreciated.

Regards
Malcolm Dowers

I can't tell you about BT BBV but i have been using a Gigaset S685IP behind a 2820VN for two years now with multiple VoIP providers ( Localphone , Sipgate , Orbtalk , Gizmo5 ) and have never experienced any dropped call problems.

Thanks Middling, are some/all your VOIPs are using STUN? Is your Gigaset on a DMZ? Did you change any of your VOIP connections UDP port numbers? I am trying to rule out things which the manufacturers is fobbing me off with as potential reasons.

Gizmo5 and Sipgate are using STUN, Localphone and Orbtalk use outbound proxies.

My Gigaset isn't currently on a DMZ. For about a year i had a block of 8 IPs, one of which was mapped 1-to-1 NAT to the Gigaset with all ports open, but for a while i've just been using a single IP for my router and NATting everything.

I haven't changed any ports on my Gigaset, but on the 2820vn i have setup the following in NAT/Open Ports and forwarded them to my Gigaset:

TCP/UDP 5060-5061
TCP/UDP 5004-5020

A few weeks ago i had a problem with not receiving incoming calls and after a bit of searching found a thread where someone claimed that in order to run a VoIP device behind a 2820vn properly you need to go through all the accounts in the 2820vn's VoIP/SIP Accounts and change all the SIP Port entries to something other than 5060 even if you aren't using the VoIP facilities of the Draytek.

I went ahead and did this and things seemed to work for a while before the problem returned. I had intermittent service for a few days then everything started working again.

I now attribute the problems i had to that fire/flood in a BT exchange but it probably couldn't hurt if you went through and changed the settings in the Draytek if you're not using them.

You could also check that you're on the latest Gigaset firmware. Mine is 022230000000 / 043.00