IP Protocol: IP Addressing

Computers and networking devices use IP addresses like a home address with the postal service.  In order for it to send and receive data it must be given a unique address other devices can use to send data to it….just like mail that’s sent to your unique home address.

Here are a few rules to IP Addressing that should be known:

  • IP addresses are 32 bit binary numbers
  • Usually IP addresses are written in dotted decimal notation with each decimal octet representing 8 bits.
  • IP Addresses are assigned to network interfaces
  • Computers with an IP address are also referred to as IP hosts.
  • Groups of IP hosts not separated from each other by a router are in the same grouping.
  • These groupings are referred to networks, subnets, or prefixes
  • IP hosts separated from other IP hosts by a router MUST be in separate networks.

IP addresses are considered classful or classless.

Classful IP addresses mean that the main class A, B, C rules from RFC791 are considered.  Class A,B and C networks are identified by their first several bits or by the range of decimal values in the first octet.

Classful IP addresses also consist of two parts, a network and a host part.  The size of the network is defined by  the class of the network.classful

Classless IP addressing means that class A, B, and C rules are ignored.  Each IP address is also seen as two parts called the prefix and host parts of the address.

the prefix defines how many beginning bits of an IP address identify the network.  All hosts with the same prefix are in the same network and can be called a  subnet or prefix.

Prefix’s must be listed with a prefix length, the prefix length is a decimal number that defines the length of the prefix.  For example a prefix ending with a /24, means that there are 24 bits used in the subnet mask….meaning you can derive the prefix length from how many active ‘1’s are turned on in the subnet mask’s bits.



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