
Configuring IP Services
1-4
Figure 1-1. Network and Host Portions of IP Addresses
You specify IP addresses in dotted decimal notation. To express an IP address in
dotted decimal notation, you convert each 8-bit octet of the IP address to a
decimal number and separate the numbers by decimal points.
For example, you specify the 32-bit IP address 10000000 00100000 00001010
10100111 in dotted decimal notation as 128.32.10.167. The most significant 2 bits
(10) in the first octet indicate that the network is Class B; therefore, the first 16
bits compose the NIC-assigned network portion field. The third octet (00001010)
and fourth octet (10100111) compose the host field.
Subnet Addressing
The concept of subnetworks (or subnets) extends the IP addressing scheme.
Subnets are two or more physical networks that share a common network-
identification field (the NIC-assigned network portion of the 32-bit IP address).
Subnets allow an IP router to hide the complexity of multiple LANs from the rest
of the internet.
8162431
8162431
8162431
0
Class A
Class B
Class C
Class A
Class B
Class C
First Octet Range Example Network Host
1-127
128-191
192-223
25.0.0.1
140.250.0.1
192.2.3.1
25
140.250
192.2.3
1
1
1
Host P tionor
Network Portion
0
1
1
0
1
1
0
1
1
1
1
0
1
1
0
1
1
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