Need some help with Networking

Alight so basically my setup is I have 2 computers and 1 laptop setup. All of them are all connected by rj45 cables through a cable router. one computer is windows xp home service pack 2, another one is media center and the lap top is xp home service pack 1. Both of my computers can connect fine on the network. but I have trouble with the Laptop. When I plug in the ethernet cable it basically
finds the ip and sub mask, but it can't find default gateway and the dns servers.
Also the sub mask on the lap top is at 255.255.0.0 while my 2 computers are on 255.255.255.0, I've been trying to get this to work for the longest time now. any ideas would be great!

Also I was trying to type in the Static IP, but i wasn't sure on how to figure out which Ip address to use and what Dns server address to use. I did find out the dns server through one of my computers and typed it in but still no luck.

Thanks in advance.

 

The subnet masks need to be the same and this can be changed in the TCP/IP properties under network connections. Are all 3 set to obtain IP address automatically?

 

yea they are all set to obtain IP address automatically, I try to type in the static ip since the lap top was still not finding the dns and sub mask was wrong. but heres my question for the static Ip which Ip address do i use? and how do i find it?

Sorry Kind of new to this networking stuff. Thanks guys

 

The IP range is found in your routers settings.