I asked this before and received no definitive answer and my initial testing led me to believe it is possible, but now I don't think it is. Let me clarify.

Is it possible to have multiple devices/clients (e.g. VigorPhones, soft phones, any other SIP phones) register SIMULTANEOUSLY to a single Vigor IPPBX extension? I hope that is clear, I am NOT referring to trunks.

My initial testing indicated that it was possible as there were no errors when the second and subsequent device registered to the same extension, but I now find that some of the registered devices don't ring or respond to calls. From this I am now thinking that in fact, the IPPBX only works with the last device that registered and since devices are continually renewing their registration, the actual device that will ring for incoming calls to that extension will be different at different times.

I tried this with 2 devices registering to the same extension. All seemed well except only one would ring on an incoming call. I then disabled the one that worked and in that case, the other would ring for any call - as it should. So both devices are working correctly. I then enabled the other one again and that 'took over' the calls again, but when I made a call from the device not currently working, that would then be the device that rang for the next incoming call.

All this points to the IPPBX only actually working with a single device on any one extension. Which device that is depends on which last registered or updated its registration in any way. So multiple devices can MAKE calls out via a single extension, but the IPPBX will only send INCOMING calls to that last registered device.

Has anyone else got any more information or experience about this?

It'd not recommend it as it's not meant to be done that way; there are other ways
to achieve what you want, probably, such as using a calling group and always
calling that rather than the individual extension number.

admin wrote: It'd not recommend it as it's not meant to be done that way;

Not recommended by who? It's part of the SIP spec and any server that does not allow it has been specifically designed to be crippled in that way to allow only a single simultaneous registration.

As for the benefits - it potentially reduces the total number of extensions required and hence simplifies the configuration. As an example, with 5 client devices (phones) each of which needs access to 5 incoming trunks (different numbers, different functions), with multiple simultaneous registrations you only need to set up 5 extensions, each of which is 'shared' by 5 clients. If only a single registration is allowed, you would need to set up 25 extensions. IOW, 5 times the work required to configure the system.

I realise Hunt Groups can be used for the same final result, but it's a lot more work than would be required if multiple registrations were allowed. My VOIP provider allows multiple simultaneous registrations to their trunks. The last IPPBX I used (SnomOne) allows multiple simultaneous registrations. It's part of SIP and it can really help to simplify an IPPBX config.

I've made the changes now to my Vigor (lots more extensions) and it seems to be working fine, but I wouldn't have had to do all that extra configuration if the Vigor allowed multiple simultaneous registrations - as it should.

Do you know where in the SIP spec that is discussed/required ?

admin wrote: Do you know where in the SIP spec that is discussed/required ?

I didn't say it was 'required', just that it's part of the capability of SIP. It's usually disallowed because the provider of the SIP server wishes to gain extra revenue by charging for each extension. But that is obviously not the case here.

I couldn't say where I read it. I was researching SIP functionality some years ago and it was quite clear that this is the way SIP is designed to work.

There are downsides to using multiple registrations to an extension. In particular, you cannot then call an individual device, unless it also has another registration to a unique extension. I've got past the problem and have all the extensions set up individually, but multiple simultaneous registrations is another technique that can be invaluable and I just think it's a shame that the Vigor is limited in this way.

Take a good look at the SnomONE IPPBX software. Available in various levels (from free upwards), for most operating systems and it has many features that would be very welcome in the Vigor IPPBX. You (Draytek?) have studied the competition haven't you?