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IP A
DDRESSING
The Internet Protocol Suite
The Internet protocol suite consists of a well-defined set of
communications protocols and several standard application
protocols. Transmission Control Protocol/Internet Protocol (TCP/IP)
is probably the most widely known and is a combination of two
of the protocols (IP and TCP) working together. TCP/IP is an
internationally adopted and supported networking standard that
provides connectivity between equipment from many vendors
over a wide variety of networking technologies.
IP Addresses and Subnet Masks
Each device on your network must have a unique IP address to
operate correctly. An IP address identifies the address of the
device to which data is being sent and the address of the
destination network. IP addresses have the format n.n.n.x where
n is a decimal number between 0 and 255 and x is a number
between 1 and 254 inclusive.
However, an IP Address alone is not enough to make your device
operate. In addition to the IP address, you need to set a subnet
mask. All networks are divided into smaller sub-networks and a
subnet mask is a number that enables a device to identify the
sub-network to which it is connected.
For your network to work correctly, all devices on the network
must have:
■
The same sub-network address.
■
The same subnet mask.
The only value that will be different is the specific host device
number. This value must always be unique.
An example IP address is ‘192.168.100.8’. However, the size of
the network determines the structure of this IP Address. In using
the Gateway, you will probably only encounter two types of IP
Address and subnet mask structures.
Type One
In a small network, the IP address of ‘192.168.100.8’ is split into
two parts:
■
Part one (‘192.168.100’) identifies the network on which the
device resides.
■
Part two (‘.8’) identifies the device within the network.
This type of IP Address operates on a subnet mask of
‘255.255.255.0’.
See Table 3 for an example about how a network with three PCs
and a Cable/DSL Secure Gateway might be configured.
Table 3 IP Addressing and Subnet Masking in a Small Network
Device IP Address Subnet Mask
PC 1 192.168.100.8 255.255.255.0
PC 2 192.168.100.33 255.255.255.0
PC 3 192.168.100.188 255.255.255.0
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