Netmask

The phrases netmask and subnet masks are sometimes used interchangeably. However, subnet masks are used primarily in network configurations, whereas netmasks usually confer with lessons of IP addresses. They are used to outline a variety of IP addresses that can be utilized by an ISP or different group.

There are three commonplace lessons of IP addresses – A, B, and C – which have the next netmasks:

Class A: 255.0.0.0
Class B: 255.255.0.0
Class C: 255.255.255.0

A Class A netmask defines a variety of IP addresses by which the primary three digit part is identical, however the different sections could every include any quantity between 0 and 255. Class B addresses have the identical first two sections, however the numbers within the second two sections could be completely different. Class C addresses have the identical first three sections and solely the final part can have completely different numbers. Therefore, a Class C IP handle vary could include as much as 256 addresses.

Technically, a netmask is a 32-bit worth used to divide sections of IP addresses. While a category C netmask is often written “255.255.255.0,” it could even be outlined as 11111111.11111111.11111111.00000000. This binary illustration reveals the 32 bits that make up the netmask (4 sections of 8 bits every). It additionally exhibits the best way the netmask “masks” the IP addresses it accommodates. The sections with all 1’s are predefined and can’t be modified, whereas the part with all 0’s could be any quantity between 0 and 255.