Specifications

Chapter 1 Understanding Networking and IP Addressing
Networking using IP
Niagara Release 2.3
Niagara Networking & Connectivity Guide Revised: May 22, 2002
1–19
type of data transmission medium used, how that medium interfaces with network
devices, and data is encoded into electronic signals for transmission through the
medium. Lastly, the physical layer defines what constitutes an acceptable signal.
IP Addressing
What is an IP
Address?
In IPv4, an IP address is a 32-bit number which uniquely identifies a host on the
Internet. It is typically written in dotted decimal form nnn.nnn.nnn.nnn (for example,
192.168.1.1 or 27.34.100.3). An IP address can be thought of as a telephone number
for your computer. A telephone number is used to direct calls to your phone. An IP
address is used to direct data to your computer (for example, displaying a web page
with your browser).
An IP address is assigned to a host by an administrator. It is not hardware specific,
but rather is configured through a software interface on each host.
Even though the address is written in the decimal form, the computer reads the
address as a series of binary digits consisting of 1s and 0s. When an IP address is
represented in dotted decimal form, each set of numbers represents eight bits, called
an octet. It takes four octets to make up each 32-bit address. For instance, the
dotted-decimal 192.128.23.14 is actually the binary number:
11000000.10000000.00010111.00001110
The conversion between the binary number (what the computer reads) and what the
administrator enters (in dotted decimal form) is illustrated in Table 1-5. Each bit of
the octet is a placeholder for a number that is a multiple of two. The multiple for each
“on” position in the octet (indicated by a 1) is added together to get the decimal
equivalent for the octet. Table 1-5 illustrates this using the 3rd octet from the
previous example (00010111).
Therefore, the largest binary number in an octet is 11111111, which is equivalent to
255 (128+64+32+16+8+4+2+1) in decimal form.
IP Classes An IP address is actually made up of two parts, the network portion and the host
portion. The network portion is used to determine whether other IP addresses are on
the local network or a remote network. All hosts on a given network share the same
network number but must have unique host numbers. Hosts on the same network can
communicate with one another without being routed through an IP router. The
network portion is analogous to an area code, which is the part of the number which
defines a group of telephone users in one area.
Table 1-5 Binary to decimal conversion.
Bit
76543210
Multiple of Two
1286432168421
Example Octet
00010111
Total
16+4+2+1=23