my girlfriend will begin working from home, and she needs to hook her Cisco 7000 series Voice over IP phone up to our existing DSL account. The phone provider's tech support said that there was no other way to configure the phone to work on our network unless we had a static IP. This sounds unnecessary, but I'm no VoIP expert. Our Internet service provider is AT&T, and the service is standard DSL. Is this a common thing to install VoIP phones? Has anybody configured phones to work off of a standard dynamic IP? What about with AT&T? AT&T is stating that they only sell static IPs in blocks of 8 which is totally unnecessary for me.
Taken from here:
A static IP makes everything a lot easier to get and keep working. Because the address remains constant you can simply leave [your VoIP service]1 to get on with it. If you have a major installation this is the only way to go. But you do need to be more careful over how you secure the server. Make sure there is nothing open to the Internet that is not absolutely essential to operation etc.
With a dynamic address every time your address changes the server needs to re-register with the service provider, or it won't work. It is not the end of the world, there are any number of scripts available that check your current address and force registration, or there is dyndns.org which will match a domain name to your continuously changing address, either method is adequate for SOHO use.
1 Original post refers to Trixbox, but this explanation applies to most VoIP phones.