DNS & using the TCP/IP FIlter

From: Glenn (type2surf-NO-SPAM_at_hotmail.com)
Date: 06/23/04

Date: Tue, 22 Jun 2004 17:04:14 -0700

I have searched the news group for problems similar to
mine and found someone with virtually the same issus i
need help with. This person seems to describe it well. it
was originally posted on jun 3 2004....

"We have a windows 2000 server running IIS for public
access with 10 public IPs. The router is broken. We would
like to enable IP filtering to open the port 80 for the
web, 25 and 110 for the mail, and TCP and UDP 53 for the
DNS (we have only one NIC with all public IPs and use our
ISP DNS) before replacing the router. Every thing looks
good except DNS. We can ping any public Ip but can't ping
the web name llike yahoo.com. Nsllokup gets the time out
too. which ports do we need to open except tcp and udp 53?
Or do we miss some things?"

Can some one please explain this. What it might be.
ANother symptom is that if I turn off the IP filtering
(leave it wide open) everything works great. Please help
as i really dont like to leave this server in this
insecure way.
Thanks for your help,