stokem wrote:
...
I like your earlier suggestion, that IVM is 'taking over' the VOIP line from the phones, so that they lose SIP registration. If that were happening, what could be done about it? Can IVM be set to take over only after the right number of rings? Or is there something that could be done in the Belkin to allow both to run together?
<{POST_SNAPBACK}>
The problem is, that this 'taking over' seems to happen on a network basis, which means, that it isn't a "call-by-call"-problem, but a general transfer of sip-traffic at all to IVM instead of your phone. (otherwise your phone would ring a least one time or very short). IVM registers to be able to get rings on your voip-line, after that, your phone is "dead", at least incoming-call wise.
IVM can't register after a defined number of rings, because it simply don't get any rings, if it is not registered....
Unfortunately I don't know your modem, so I can't say anything about the possible configurations of network traffic routing etc. of your belkin modem.
Could you find anything in your manual about NAT (Network Address Translation) and how IP-adresses have to be configured?
I'm afraid, you have to investigate a bit deeper to find some solution. You could for example use different voip-providers for your phone and IVM to check if it is possible at all, to receive sip-traffic at both ends parallel. May be your sip-provider simply doesn't support the registering of more than one device. (which would be uncommon but who knows...)
regards

Tjareson.