[CentOS] DNS or firewall problem

>> Are you running a proxy for http? It would be rather 
>> surprising that internal machines can access the Internet 
>> without forwarding turned on otherwise. When you say internal 
>> machines cannot access your server, are they connecting to it 
>> via the local interface's ip or the Internet ip? 
>> Are the services bound to the local interface?
> 
> 
> I did notice today there is a squid.conf file in my /etc/httpd/conf.d
> directory. It appears it is configure for the local domain only.  I renamed
> it and restarted apache but that didn't work.
> 
> The server has two nics, one for internet and one for the local network,
> connected to a switch. eth0 is connected to the uplink port.

Please pastebin the output of the following:
Run as root:
'cat /etc/sysconfig/iptables'
'netstat -ntlp'