Firewall settings

I'm on wireless internet on my laptop, and everynow and again, the last digit of my IP address seems to change from .2 to .3 and then within time it goes back again.
This is realy annoying me becasue to make my bittorrent client not firewalled, I've set the router on a DMZ setting so it recognised my computer as connected to the network differently or something? I'm not entirely sure what the DMZ setting does, but it seems to work. It lets me type in one specific IP address and then I tick the "Enable" box.
I was wondering if there was any way I could stop my IP address from changing about?
Thanks, Josh.

 

open the properties for your wireless connection, hilite the tcpip protocol & click the properties button, and (see attachment) it will probably be set to obtain an ip address automatically from your wireless router. it will normally pick up the next address in the range, ie. on mine it would pick up 192.168.2.2 but might pick up 192.168.2.3 if someone else in the house connects before me. i thus use a fixed ip ending in .17 to ensure i can get the one i want for other settings.

you can select the other option and use a fixed ip as i do in the attachment. note that the gateway is the ip address of your router. the dns server should normally be set to the router address if your router acts as a dns cache or to your isp's dns servers. i show the addresses of the opendns servers, but have the third address of my router in the advanced properties which allows you to add more...

if you also connect to other networks or access points with different ip ranges you will need to change the fixed address/gateway every time you switch, which is the down side.