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IP Address


  • 32-bit address
  • Broken down into 4 octets
  • The address is split into network portion and host portion based on the subnet mask
  • They are classified as:
    • Classfull addresses: 
      • The IP address range is divided among five classes namely A, B, C, D, E
      • Each class has a specific set network portion and host portion
      • It’s obsolete 
    • Classless addresses:
      • There is no fixed network and host portion
      • The subnet mask is used to determine the network and host portion
  • Private IP addresses:
    • These IP address ranges are not available for usage on the public internet
    • They are meant to be used for internal/private networks
  • CIDR (Classless Inter Domain Routing)
    • It’s convenient notation to specify the network portion of an IP address
    • Ex. /16 means the first 16 bits of the IP address form the network portion
  • All 0’s in the host portion means it’s a network address
  • All 1’s in the host portion means it’s a broadcast address


  • 128-bit address
  • It’s widely accepted standard to use the first 64 bits as the network portion and other 64 bits as the host portion
  • The address is split in to 8 hextets 
  • 4 Hexadecimal digits are used to represent each of the hextets
  • In order to shorten the address leading zeros may be replaced with ::
  • IPv6 addressing is still not widely used in the internet and so to connect to IPv6 enabled networks IP tunnelling is used

Subnet masks#

  • Subnet masks are used to identify the network and host portions of an IP address