Skip to content

Subnet-Mask.md

Latest commit

 

History

History
48 lines (30 loc) · 1.5 KB

Subnet-Mask.md

File metadata and controls

48 lines (30 loc) · 1.5 KB
Raw

Subnet Mask / Netmask / Network Mask

A Subnet Mask (also called Netmask or Network Mask) is used in IP networking to divide an IP address into network and host portions. It tells which part of the IP address identifies the network and which part identifies the device (host).

Network Mask Structure

  • Total Bits: 32 bits (just like an IPv4 address)

  • Sections: 4 sections (octets)

  • Bits per Section: 8 bits each

  • Representation: Binary or Decimal (e.g., 11111111.00000000.00000000.00000000 = 255.0.0.0)

  • Binary Pattern:

    • Network part: All bits are 1
    • Host part: All bits are 0

Subnet Masks by IP Class

Class A

  • Example IP: 1.0.0.1
  • Structure: N.H.H.H (Network.Host.Host.Host)
  • Binary Mask: 11111111.00000000.00000000.00000000
  • Decimal Mask: 255.0.0.0

Class B

  • Example IP: 128.0.0.1
  • Structure: N.N.H.H (Network.Network.Host.Host)
  • Binary Mask: 11111111.11111111.00000000.00000000
  • Decimal Mask: 255.255.0.0

Class C

  • Example IP: 192.0.0.1
  • Structure: N.N.N.H (Network.Network.Network.Host)
  • Binary Mask: 11111111.11111111.11111111.00000000
  • Decimal Mask: 255.255.255.0

Purpose of a Subnet Mask

  • Identifies how many bits are used for the network and how many for hosts.
  • Helps routers understand where to send packets.
  • Enables subnetting, which breaks large networks into smaller, manageable parts.