Something that a lot of people wonder is why do so many routers and other forms of network equipment use IP's like 192.168.0.1 as their default IP address? The short answer is it is the first IP from within a private IP range specified by RFC 1918 as non routeable from the internet. This reserves IP's for us to use on our internal networks.

Link to the standards of RFC 1918.
http://www.ietf.org/rfc/rfc1918.txt?number=1918
http://www.faqs.org/rfcs/rfc1597.html

TCP/IP addresses reserved for 'private' networks are:
10.0.0.0 to 10.255.255.255
172.16.0.0 to 172.31.255.255
192.168.0.0 to 192.168.255.255
and as of July 2001
169.254.0.0 to 169.254.255.255
http://compnetworking.about.com/cs/...bldef_apipa.htm
http://msdn.microsoft.com/library/d...tocol/apipa.asp

Since the 192.168.0.0/24 range is the de facto default network on home networking equipment, I typically change my private network to a 10.0.0.0-something/24 just to make things that much more difficult for someone trying to get in from the outside. Hackers + defaults = bad.

Additional reading can be found on wikipedia in the usual easy to read format here: http://www.wikipedia.org/wiki/Private_IP_address

You will want to read the member comments about this: Also please add additional information you think people should know.