Understanding IP Address Structure, Classification, and Basic Router Configuration

The primary purpose of an IP address is to identify a network node.

Composition

An IPv4 address consists of 32 binary bits, commonly represented as four decimal octets such as 192.168.1.1, and is divided into a network portion (identifying the network) and a host portion (identifying a specific device within that network).

IP Address Classification

Class

Range

Use

A

Network+Host+Host+Host 1~126

Largest number of hosts, used in large networks

B

Network+Network+Host+Host 128~191

Medium‑sized network environments

C

Network+Network+Network+Host 192~223

Small networks with few hosts

D

224~239

Multicast communication

E

240~255

Reserved for scientific research

Private Addresses

10.0.0.0 – 10.255.255.255 /8

172.16.0.0 – 172.31.255.255 /16

192.168.0.0 – 192.168.255.255 /16

Subnet Masks

Class A: 255.0.0.0 /8

Class B: 255.255.0.0 /16

Class C: 255.255.255.0 /24

Configuring Network Connectivity

R1 Configuration

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#int fa0/0

R1(config-if)#ip address 192.168.200.1 255.255.255.0

R1(config-if)#no shutdown

R2 Configuration

R2#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R2(config)#int fa0/0

R2(config-if)#ip address 192.168.200.2 255.255.255.0

R2(config-if)#no shutdown

Testing