here is the case :-
- i have got 2 computers one of them is a DC
- the DC name is Domain.com
- the client which is running winxp named ( compaq )
- iam behind a router and the DC has two network interface cards one is 3com i named it ( External ) and the other is compaq NIC and i named it ( internal )
- i pluged the UTP cable that came from the router into the (External) however the other one ( Internal ) linked to a switch , and then the switch linked to the Compaq computer .

- i have created a computer account named ( compaq ) in active directory and a username called ( sameh ) with the appropociate permissions to join the client computer to the domain controler .

- the network configuration of the External card is :-
ip : 10.0.0.100
Subnet : 255.255.255.0
Gateway: 10.0.0.138 <--- the router's ip
DNS : 10.0.0.138

-------------------------

- the network configuration of the External card is :-
ip : 10.0.0.88
Subnet : 255.255.255.0
Gateway: 10.0.0.100 <--- the DC's ip
DNS : 10.0.0.100

- the network configuration of the Client computer is :-

ip : 10.0.0.99
Subnet : 255.255.255.0
Gateway: 10.0.0.100 <--- the DC ip
DNS : 10.0.0.100

******** the problem that i can not join the client computer to the domain and it gives me the following error *** A Domain controler for the domain domain.com could not be contacted ensure that the domain controler typed correctly .

please help me with this essue :(((

You've got 10.0.0.99 as your internal NIC address on the server as I understand the above. And, you have the gateway address set on the client as 10.0.0.100. That's the problem. Set your Gateway address on the client to the IP address of the server (ie: 10.0.0.99) and things should work.

Also, you may want to remove the gateway address on the internal NIC on the server. It does it's own routing internally and that address is unnecessary.

I should have explained a little better. The 10.0.0.100 address is your External address. The external NIC is the one not connected to your internal network (ie: it's connected to your external network - the internet).

Your internal network address is 10.0.0.99 and this is the address your client(s) should be using for their DNS and Gateway addresses.

As I said before, if you're using RRAS/NAT, or even ICS, your server will handle it's own routing between the internal and external interfaces internally and you don't require a Gateway address on the internal NIC.

Thanks you so much for replaying mate ,

i have solved the previous issue , and everyhint is going fine however , i have got another problem which is that the client can NOT ping the ISA server , therefor it can NOT resolve the name or even the IP of the ISA server when i try to make it firwall client , even when i set the client as a secure NAT client it doesn't connect to the internet although i have my ISA server allready connected to the internet and the rules are applied .

iam not sure if its a routing problem or a DNS problem , please try to help me .

thanks and regards