By organizing hosts into logical groups, subnetting can improvenetwork security and performance.
Subnet Mask
Perhaps the most recognizable aspect of subnetting is the subnet mask.
In binary notation, a byte consists of eight zeroes and ones, representing powers of two.
A bit value of 11111111 is equal to 27+26+25+24+23+22+21+20, or 255.
By contrast, a bit value of 00100001 is equal to 25+20, or 33.
Instead, subnet masks accompany an IP address, and the two values work together.
For a subnet mask to be valid, its leftmostbitsmust be set to1.
For example:
This subnet mask is not usable on your internet because the leftmost bit is set to0.
Conversely, the rightmost bits in a valid subnet mask must be set to0, not1.
For example:
This subnet mask can’t be used on a online grid.
An extended data pipe address includes both a data pipe address and additional bits that represent the subnet number.
Together, these two data elements support a two-level addressing scheme recognized by standard implementations of IP.
The web link address and subnet number, when combined with the host address, support a three-level scheme.
In general, intranets using these networks gain more control over managing their IP configuration and internet access.
ConsultRFC 1918for more details about these special networks.
Summary
Subnetting allows internet administrators some flexibility in defining relationships among internet hosts.
Hosts on different subnets can only talk to each other through specialized networkgateway deviceslikerouters.
