Managed to sneak it though. I had the unfortunate circumstance (bs speak for 'poor plannig') of having my name servers aprt of the ip address change. THe long and the short of it, I cheated an iptables entry into smoothwall 2.0 so that I could at least get dns to resolve properly until the root servers get updated. "Bad admin. No Starbucks for _you_!"
Added an alias eth1:1 with the old IP and used the new IP for eth1. The following snippet was for the old IP addy. This should not have worked, but it apears to.
iptables -t nat -A PREROUTING -i eth1 -p UDP -d ex.ter.nal.ip --dport 53 -j DNAT --to in.ter.nal.ip:53
iptables -A FORWARD -i eth1 -o eth0 -p UDP -d in.ter.nal.ip --dport 53 -j ACCEPT
Shameless hack and not really what iptables is all about, but the mail is barfing in now at a nice clip after being offline for, oh... six hours. I would have fired me in a heartbeat. Maybe I should just get back into construction. Decent wage, coffee breaks, travel, no firewalls...