What Are The Different IP Classes?

IP Addresses are split up into 5 different classes. You can tell which class an IP is in by looking at the first octet (everything before the first dot) of the address. Here is a list explaining each class, as well as any reserved addresses.

Class A
First bit is always 0

First byte: 0 - 127
Reserved sets: 0 and 127

Example: 5.26.44.200
Example reserved: 127.0.0.1

126 available Class As exist
16,777,214 hosts on each Class A

Class B
First 2 bits are always 10

First byte: 128 - 191

Example: 144.30.114.124

16,384 Class Bs exist
65,532 hosts on each Class B

Class C
First 3 bits always 110

First byte: 192 - 223

Example: 192.168.1.115

2,097,152 Class Cs exist
254 hosts on each Class C

Class D
First 4 bits always 1110

First byte: 224 - 239

Example: 224.0.0.0

Used for multicast

Class E
First 4 bits always 1111

First byte: 240 - 255

Example: 255.100.102.50

Reserved, used for experimental purposes.

Why Learn It?

It is useful to learn this stuff for two reasons - It makes you look smart and it actually makes you smarter.

It is a good idea to memorize as much terminology as you possibly can. While the names Class A, B, D, and E are not used as much during discussions, Class C will often pop up. A perfect example is with HostGator’s new SEO Hosting service.

Let’s say for example a hosting company says it will get you your own Class C address. All that means is the first octet of the address (everything before the first dot) will be between 192 - 223 (inclusive) like 207.25.44.67. It has nothing to do with the other octets.

What About IPv6?

IPv6 does not use classes, instead it recognizes addresses as being unicast (normal communications between two devices), multicast (sending data to multiple devices), or anycast (only send data to the nearest devices as defined by routing technology).

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