The Subnet Mask

In this article we will discuss The Subnet Mask, will make brief discussion on The Subnet Mask, In last article we discuss about The Need for IPv6.

Three dotted decimal IPv4 addresses must be configured when assigning an IPv4 configuration to host:

  • IPv4 address – Unique IPv4 address of the host
  • Subnet mask– Used to identify the network/host portion of the IPv4 address
  • Default gateway – Identifies the local gateway (i.e. local router interface IPv4 address) to reach remote networks

When an IPv4 address is assigned to a device, the subnet mask is used to determine the network address where the device belongs. The network address represents all the devices on the same network.

The dotted decimal address and the 32-bit subnet mask. Notice how the subnet mask is essentially a sequence of 1 bits followed by a sequence of 0 bits.

To identify the network and host portions of an IPv4 address, the subnet mask is compared to the IPv4 address bit for bit, from left to right. The 1s in the subnet mask identify the network portion while the 0s identify the host portion. Note that the subnet mask does not actually contain the network or host portion of an IPv4 address, it just tells the computer where to look for these portions in a given IPv4 address.

The actual process used to identify the network portion and host portion is called ANDing.

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