In the interest of future readers and basic stuff, one thing that might be helpful to mention is about local IP addresses.
If you can't seem to connect to your VoIP box or router, then change the IP address of your computer such that the first three parts of the IP address are the same, and the last one different. This is especially a pro pos if you
change the IP address of your VoIP box or router. For example, my 2102 came loaded with a static IP of 192.168.0.1, but my router was 192.168.1.1, and was handing out dynamic IP addresses starting at 192.168.1.100. So, I wanted to change the VoIP to 192.168.1.1 and the router to 192.168.1.2. As soon as I changed the IP of the VoIP, I lost connection with it, and even after typing in
http://192.168.1.1 (the router was off-line, powered down, and already changed to 192.168.1.2 in any event), I got nothing. I immediately knew why and went into my network settings and set the IP of the laptop to 192.168.1.107, and
then reloaded the URL of the VoIP box GUI, and
voila, I had access again. If your subnet mask is 255.255.255.0, it means that the first three parts of the IP address of all the things on the LAN had better be the same, otherwise, they ain't all on the same LAN and won't talk to a web GUI that requires you be on the same LAN.
Oh, and that also means that if your VoIP or router or whatever is a DHCP server, that you probably want it to be giving out local IP addresses that have the same first three numbers as itself. i.e. before I changed the 2102, it's IP was 192.168.0.1, and it was giving out IP addresses starting at 192.168.0.2. I changed its IP to 192.168.1.1 and had it hand out IP addresses starting at 192.168.1.100. I had to make both changes. Think of the first three numbers as putting all the stuff on the LAN in the same room, and the fourth number giving them ID numbers so they can recognize and talk to each other. If you give two people the same number, it's bad, as they both answer to the same ID. Bad!
Please correct anything that isn't quite right here, ElectronGuru. Thanks!