If my ISP gives me an IP with a subnet mask of 255.255.248.0. Does this mean I have an 8 IP subnet?

Sorry to say but I think you have only 1 IP address. Your provider is just using larger subnets for their DSL service. In this case your on a submit that can have 8 times the hosts of a 255.255.255.0 subnet. They're probably usind CIDR (see a href="http://en.wikipedia.org/wiki/Clless_Inter-Domain_Routing" rel="nofollow"http://en.wikipedia.org/wiki/Clless_I…/a ) to break up one larger block of IP addresses into a bunch of smaller subnets. With CIDR you don't need to have clean 255's in each field of the subnet.