Subnet Mask Explanation

What is a Subnet Mask?

• A subnet mask is used in networking to divide an IP address into two parts: the network address and the host address.
• It helps identify which part of an IP address refers to the network and which part refers to the device (or host) on that network.

Subnet Mask Notation

• Subnet masks are usually notated in dot-decimal format.
• Example: 255.255.255.0
  • This specific subnet mask indicates that the first three octets (255.255.255) are used for the network address.
  • The last octet (0) is used for the host address, allowing for 256 possible addresses (0-255) within this network.

Understanding 255.255.255.0

• 255 in binary: 11111111
• 0 in binary: 00000000
• A subnet mask of 255.255.255.0 implies a network prefix of 24 bits (also expressed as /24).
• This configuration is common for small to medium-sized networks.

Practical Use

• Allows for up to 254 possible hosts (devices) in the network, as two addresses are reserved:
  • One for the network address.
  • One for the broadcast address.

Importance of Correct Subnet Mask

• Ensures proper network segmentation and efficient use of IP addresses.
• A correct subnet mask prevents potential network conflicts and improves network security.