A unique IP address is required for each host using TCP/IP. Network applications that use TCP/IP identify other network hosts using IP addresses. The IP address provides the directions to the exact location of a host device on a network.
If IP determines that a destination address is an address on the local network, IP transmits the packet directly to the network host. If IP determines that the destination IP address is not on the local network, IP looks for a route to a remote host. An address on the local network is a local address and an address not on the local network is a remote address. If a route is found, IP sends the packet using that route. If a route is not found, the packet is sent to the source host's default gateway. A gateway is a device that connects networks using different communication protocols.
Note Windows CE supports one default gateway.
Each IP address defines a network identifier and a host identifier. The network identifier identifies systems located on the same physical network. All systems on the same physical network must have the same network identifier. The host identifier identifies a workstation, server, router, or other TCP/IP host within a network. The address for each host must be unique to the network identifier.
Each IP address is 32 bits long and composed of four octets, or 8-bit fields. An octet is a decimal number in the range from 0 through 255. Each octet is separated by a period. This format is called dotted decimal notation. The IP address 224.0.1.24 is an example of dotted decimal notation.