Machines on the LAN use DHCP. The firewall box uses DHCP to get its IP address (from the ATT server) and runs dhcpd to hand out IP addresses (in 192.168.*.* range) to LAN machines. If a LAN machine gets a bizarre IP address that wasn't handed out by the firewall dhcpd, don't assume ATT's server is responding. Many machines (OS X and Windows 98 to name two) appear to randomly assign addresses if nobody responds. Bungholes!