I'm having a bit of a problem with two of my new phones. I'm wanting to connect 3 phones behind a nat to pbxes. The siemens s450ip connects without any problems. However the sip cisco 7960 phones just won't register. I have tried everything to my knowledge; turned nat on the phones on, used a different pbxes server on each phone, using different ports. All 3 phones are able to connect to a Voipcheap account and make phonecalls. Even when the siemens phone that does connect is removed from the network, the cisco phones still won't register, they never have!
