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U nderstanding IPv4 Addresses

An IP Address is a logical address used in order to
uniquely identify a device on an IP network.

  • It’s a Network Layer Address
  • There are Two Versions:
    • IP version 4 (IPv4)
    • IP version 6 (IPv6)
      • This course focuses on IPv4 Addresses

An IP Address is made up of 32 binary bits, which can be divided into a network portion and a host portion with the help of a subnet mask.

  • The 32 binary bits are broken into four octets (1 octet = 8 bits).
  • Each octet is converted to decimal and separated by a period (dot).
    • For this reason, an IP address is said to be expressed in dotted decimal format.

An IP address is broken down into two parts:

Network Address

  • Uniquely identifies each network
  • Your Street Name: 7682 Wilshire Drive

Host Address

  • Uniquely identifies each machine on a network
  • Your House Address: 4682 Wilshire Drive

Network Address + Host Address = IP Address

  • 4682 + Wilshire Drive = 4682 Wilshire Drive


Each device on a network is assigned an IP address, subnet mask and default gateway:

  • IP Address: Unique logical address assigned to each device on a network.
  • Subnet mask: Used by the device to determine what subnet it’s on.
  • Default Gateway: The router’s IP address that allows the device to communicate outside it’s local subnet.

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