Digi RCM4000 - Manual (Page 73)

User’s Manual 67
6.2.1 IP Addresses Explained
IP (Internet Protocol) addresses are expressed as 4 decimal numbers separated by periods,
for example:
216.103.126.155
10.1.1.6
Each decimal number must be between 0 and 255. The total IP address is a 32-bit number
consisting of the 4 bytes expressed as shown above. A local network uses a group of adja-
cent IP addresses. There are always 2
N
IP addresses in a local network. The netmask (also
called subnet mask) determines how many IP addresses belong to the local network. The
netmask is also a 32-bit address expressed in the same form as the IP address. An example
netmask is:
255.255.255.0
This netmask has 8 zero bits in the least significant portion, and this means that 2
8
addresses are a part of the local network. Applied to the IP address above
(216.103.126.155), this netmask would indicate that the following IP addresses belong to
the local network:
216.103.126.0
216.103.126.1
216.103.126.2
etc.
216.103.126.254
216.103.126.255
The lowest and highest address are reserved for special purposes. The lowest address
(216.102.126.0) is used to identify the local network. The highest address
(216.102.126.255) is used as a broadcast address. Usually one other address is used for the
address of the gateway out of the network. This leaves 256 - 3 = 253 available IP
addresses for the example given.