Which of the following address belongs Class A?

"Class A" IPv4 addresses are for very large networks. Please note below important points about Class A network IP addresses.

• First octet of a "Class A" network IP address is used to identify the "Network part" and the remaining three octets are used to identify a host uniquely within that network.
• The default structure of a Class A IP address is Network.Host.Host.Host
• The left-most bit (also called as high-order bit or most-significant bit) of the left most octet of a "Class A" network is reserved as "0".

I strongly suggest you to visit and learn below lessons before you continue learning more about Class A networks and Class A IP addresses.

• IPv4 Addresses
• What is subnet mask
• What is network address
• Binary Decimal and Hexadecimal numbers and conversions
• Five layered TCP/IP model
• Network Layer (Layer 3)
• IPv4 Protocol, IPv4 header and fields of IPv4 header
• Media Access Control (MAC) addresses
• Limited broadcast address
• Directed broadcast address
• What is Loopback address

Structure of a Class A IP address

The left-most octet of a Class A network IP address belongs to the network part and remaining three octets belongs to the host part. The structure of a Class A IP address is Network.Host.Host.Host. The default subnet mask of a Class A IP address is 255.0.0.0.

Please refer below image.

The number of networks and the number of hosts per class can be derived by this formula −

When calculating hosts' IP addresses, 2 IP addresses are decreased because they cannot be assigned to hosts, i.e. the first IP of a network is network number and the last IP is reserved for Broadcast IP.

Class A Address

The first bit of the first octet is always set to 0 (zero). Thus the first octet ranges from 1 – 127, i.e.

Class A addresses only include IP starting from 1.x.x.x to 126.x.x.x only. The IP range 127.x.x.x is reserved for loopback IP addresses.

The default subnet mask for Class A IP address is 255.0.0.0 which implies that Class A addressing can have 126 networks (27-2) and 16777214 hosts (224-2).

Class A IP address format is thus: 0NNNNNNN.HHHHHHHH.HHHHHHHH.HHHHHHHH

Class B Address

An IP address which belongs to class B has the first two bits in the first octet set to 10, i.e.

Class B IP Addresses range from 128.0.x.x to 191.255.x.x. The default subnet mask for Class B is 255.255.x.x.

Class B has 16384 (214) Network addresses and 65534 (216-2) Host addresses.

Class B IP address format is: 10NNNNNN.NNNNNNNN.HHHHHHHH.HHHHHHHH

Class C Address

The first octet of Class C IP address has its first 3 bits set to 110, that is −

Class C IP addresses range from 192.0.0.x to 223.255.255.x. The default subnet mask for Class C is 255.255.255.x.

Class C gives 2097152 (221) Network addresses and 254 (28-2) Host addresses.

Class C IP address format is: 110NNNNN.NNNNNNNN.NNNNNNNN.HHHHHHHH

Class D Address

Very first four bits of the first octet in Class D IP addresses are set to 1110, giving a range of −

Class D has IP address range from 224.0.0.0 to 239.255.255.255. Class D is reserved for Multicasting. In multicasting data is not destined for a particular host, that is why there is no need to extract host address from the IP address, and Class D does not have any subnet mask.

Class E Address

This IP Class is reserved for experimental purposes only for R&D or Study. IP addresses in this class ranges from 240.0.0.0 to 255.255.255.254. Like Class D, this class too is not equipped with any subnet mask.

Which of the following is Class A address?

What is the range of Class A?

What are the 4 types of IP address?

What are classes of IP address?