Can't anyone explain it to me?
asked Oct 20 '10 at 13:53
Given an IPv4 address (100.100.100.1, for example), the Subnet Mask determines how much of that address space is used for local vs remote connections.
For example, if you have a network 192.168.0.* and a subnet mask 255.255.255.0, then you have address space for 255 addresses in your network (which is like 252 devices due to reserved numbers). If you used 255.255.0.0, you'd get 65536, and if you used 255.255.255.255, you'd get zero.
Once an address goes beyond the subnet mask, it's deemed to be on the outer network; in most cases, the Internet. This prevents your DNS server from assigning you an IP address that belongs to Yahoo.
answered Oct 20 '10 at 15:07