I have created a name server (With Windows Server 2003) and published it to the internet. I also created DNS zones and everything was working just fine. I was able to ping that name server from outside our network i.e. from the internet. I was also successful in doing a DNS Lookup. But, as soon as I installed ISA server 2000 SBS, everything stopped working. Now, I am unable to ping or perform a DNS lookup from outside our network i.e. the internet. But, I am able to access the internet from within our network. I have installed ISA 2K SP2 and also its hotfix. But, still its not working. I think there is some problem with the ISA Firewall configuration.
In the Access Policy / IP Packet Filters section, you need to add in the predefined protocols, ICMP Ping Query & ICMP Ping Response (or something along those lines) else ISA Server will just kill the request