[c-nsp] DNS and NAT

[Roy]

I am trying to setup a Linux box behind a Cisco router that has NAT 
turned on.
I configured:

ip nat inside source static udp 10.10.100.20 53 xx.xx.xx.xx 53 extendable
ip nat inside source static tcp 10.10.100.20 53 xx.xx.xx.xx 53 extendable

If I do

dig . @xx.xx.xx.xx

 From the internet, I get the proper response.  tcpdump on linux shows 
the packet arriving and a response packet.

If I do

dig domain.com @xx.xx.xx.xx

I get no response.  tcpdump on the linux box shows a reply packet 
leaving it and the router responding with ICMP host unreachable.

Software is

IOS (tm) C1700 Software (C1700-K9O3SY7-M), Version 12.3(18), RELEASE 
SOFTWARE (fc3)

Any ideas are welcome.

Roy