Classful Subnetting

Class A IP Address

An IP address with 8 bits for the network address and 24 bits for the host address, with a default subnet mask of 255.0.0.0.

Class B IP Address

An IP address with 16 bits for the network address and 16 bits for the host address, with a default subnet mask of 255.255.0.0.

Class C IP Address

An IP address with 24 bits for the network address and 8 bits for the host address, with a default subnet mask of 255.255.255.0.

Class D IP Address

IP addresses used for multicast communication, ranging from 224 to 239.

Class E IP Address

Reserved IP addresses for future use or experimental purposes, ranging from 240 to 255.

Subnet Mask

A 32-bit number that divides an IP address into network and host portions.

Network Address

An address that represents the network itself, with all host bits set to 0.

Broadcast Address

The last IP address in a subnet, with all host bits set to 1.

First Usable Host Address

The first IP address that can be assigned to a device on a subnet, which is one more than the network address.

Last Usable Host Address

The last IP address that can be assigned to a device on a subnet, which is one less than the broadcast address.

IP Address Classification

The method of identifying the class of an IP address based on the value of the first octet.

Default Subnet Mask for Class A

255.0.0.0

Default Subnet Mask for Class B

255.255.0.0

Default Subnet Mask for Class C

255.255.255.0

How to determine the class of an IP address?

Check the value of the first octet: Class A (0-127), Class B (128-191), Class C (192-223).

What bits represent a Class A address in binary?

The first bit is 0.

What bits represent a Class B address in binary?

The first bits are 1, 0.

What bits represent a Class C address in binary?

The first three bits are 1,1,0.

What range does a Class D address cover?

224 to 239.

What range does a Class E address cover?

240 to 255.