Help connnecting to internet...IP address

My brother's macbook pro 10.6.8 cannot connect to the same internet as myself. When going to his system preferences > network > advanced > TCP/IP... his IP address has self assigned to the wrong IP. Also his subnet mask is missing a series of numbers than mine has. The last difference between his network preferences and mine is that his laptop cannot find the router (linksys)

We have tried rebooting the router and computer multiple times and manually assign the IP address with no success.

Any help would be appreciated
Thanks

Give this a shot to start with.

System Preferences - Network - highlight the connection being used - ethernet or Airport - click the Advanced button - in the Preferred Networks box, highlight and delete everything in there - then click the plus sign and add the network back in.