What is Internet Protocol Tutorial?

The IPv4 address space can be subdivided into five address classes called Class A, B, C, D and E. Each class consists of a contiguous subset of the overall IPv4 address range.

IP Address Classes and Numbering

The values of the leftmost four bits of an IPv4 address determine its class. For example, all Class C addresses have the leftmost three bits set to '110', but each of the remaining 29 bits may be set to either '0' or '1' independently (as represented by an x in these bit positions):

110xxxxx xxxxxxxx xxxxxxxx xxxxxxxx

Converting the above to dotted decimal notation, it follows that all Class C addresses fall in the range from 192.0.0.0 through 223.255.255.255.

The table below describes the IP address values and ranges for each class. Note that some of the IP address space is excluded from Class E for special reasons as described further below.

IPv4 Address Classes
ClassLeftmost bitsStart of RangeEnd of Range
A0xxx0.0.0.0127.255.255.255
B10xx128.0.0.0191.255.255.255
C110x192.0.0.0223.255.255.255
D1110224.0.0.0239.255.255.255
E1111240.0.0.0254.255.255.255

 

IP Address Class E and Limited Broadcast

The IPv4 networking standard defines Class E addresses as reserved, meaning that they should not be used on IP networks. Some research organizations use Class E addresses for experimental purposes. However, devices that try to use these addresses on the Internet will be unable to communicate properly.

A special type of IP address is the limited broadcast address 255.255.255.255. A network broadcast involves delivering a message from one sender to many recipients. Senders direct an IP broadcast to 255.255.255.255 to indicate all other nodes on the local area network (LAN) should pick up that message.

This broadcast is 'limited' in that it does not reach every node on the Internet, only nodes on the LAN.

Internet Protocol officially reserves the entire range of addresses from 255.0.0.0 through 255.255.255.255 for broadcast, and this range should not be considered part of the normal Class E range.

IP Address Class D and Multicast

The IPv4 networking standard defines Class D addresses as reserved for multicast. Multicast is a mechanism in Internet Protocol for defining groups of client devices and sending messages only to that group rather than to every device on the LAN (broadcast) or just one other node (unicast).

Multicast is mainly used on research networks. As with Class E, Class D addresses should not be used by ordinary nodes on the Internet.

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