If you ever wondered if an interface with a dhcp obtained address can also have static aliases assigned to it, stop wondering. It can. That said, some (probably most) firewall distributions don’t allow setting aliases if your external IP is obtained via DHCP. I’m looking at you, IPCop (UPDATE: no longer developed). I thought maybe my ISP was the only one that did this to provide static IP addresses to it’s customers, but AT&T also does it, as I’m sure others do too, since I’ve seen a few posts on how to setup such a beast for firewall purposes. Because my beloved IPCop wasn’t up to the task, I ended up using a vanilla install of Ubuntu server, and I used webmin to setup the firewall using iptables. I detailed that process in the post Wall.