DNS server problem

[Rahul Garg]

Well, the detailed  description of the problem is  :

I want to make my linux m/c  a linux server (intranet).I have made it a DNS server(internal).and file server(Samba)
I have configured a modem on linux server.
when i connect to internet it appends two lines to /etc/resolv.conf
nameserver  ipaddress  
nameserver ip address 
and it removes ipaddress of internal dns server.
#These ip addressses comes same everytime i connect to internet.I have not provided these ip addresses anywhere.
moreover the default gateway which is set to linux server also changes which i think is dynamicaly
provided and can be seen thru /sbin/route.

and when i ping google.com it pings even when my   DNS server  ' named' daemon is not running.
what i want is when i ping it should look for local dns server to resolve the ip address and if not resolved it should look 
the named.conf file where the
 
 forwarders{ipaddress;}; option is provided.
It should not be able to ping if named daemon is not running.
also, if i want to make my linux m/c as gateway server  i think i have to make 
forwardipv4 option to yes in /etc/sysconfig/network file.an gateway option as ipaddress of the linux m/c..Is this enough
to make it the gateway server without any firewalls which i would it after sometime.
on client m/c what i want is my client window m/cs connected to linux server should be able to connect to internet thru linux server.
on client m/cs i have provided the gatewayand dns server as the ipaddress of linux server.i am able to ping local m/cs thru client m/cs but not the internet.

 
Any suggestions will be helpful. 

Thanks,
Rahul