Red Hat Linux 6.2 acting as a firewall and cache server with two network cards for an NT network. The internet comes into a router. That router plugs into the linux firewall's external card. Then an internal card connects to the private lan.

It works great with one server and workstations. They are able to ping each other's private ip's and get out to internet.

My problem is that the existing MS Exchange server, once changed over to private ip will not ping the linux box, and the linux box will not ping the exchange server. From the linux box, I get destination host unavailble or whatever that error is.

The exchange server has the linux box as a gateway, and an internal ip. It's configured just like the other computers that do work thru the firewall. The exchange server does act as the WINS server, but I don't see what this has to do with simple ping.

Anyone have any ideas, thanks in advance.

You do not write which Ip-adresses that you computers have (Not good for security) but it would be a good help.
Let's make a little example
comp. nr1 Ip-adress 10.0.0.1 (firewall)
submask 255.0.0.0

comp nr 2 Ip-adress 10.0.0.15 (client)
submask 255.0.0.0

comp nr3 Ip-adress 192.168.0.14 (Client)
submask 255.255.255.0

then comp nr 1&2 have no problems "talking" with each other, but they can not talk with nr3 because the nr 3 have an class c Ip-adress and a different submask.
The nr 1&2 have an class A ip-adress
so if you want to make them all talk togeather you should assign e.g. ip-adress 10.0.1.14 and submask 255.0.0.0 for computer nr 3
so shortly computers should have an Ip-adress within the same class (Class A,b or C)and the same submask
I can remember the ip-adresses that are assigned to each class but you should be able to find some info on that subject somewhere on the net :-) (Or ask someone here)

Hope this could be of any help

Morten Torp