[jazzbo]

Originally Posted by myron

All was fine before, but all directions I can find make it clear that you must be set up with a static ip address to forward ports. Comcast forced me to switch to dynamic. Now I receive NAT errors no matter what I do.

Okay, there are two different sets of IPs -- one is a WAN and one is LAN. The IP assigned by your ISP (Comcast) to your connection is the WAN and the IP you assign to the machines behind your modem/router is the LAN. These should be in a protected range and will start with one of the following:

10.x.x.x
172.16-31.x.x
192.168.x.x

It is this second set of LAN IPs which most port forwarding instructions say should be static in order for port forwarding to work correctly.

Theoretically every time your router renews it lease through the modem it could be given a new WAN IP, but that shouldn't matter as it will still forward connections on the selected port back to the staticly assigned LAN IP on your local network. If you have access to the router, you have the ability to determine if your computer gets a static or dynamic IP on the LAN.