Full Form of CIDR

CIDR is a short form that stands for Classless Inter-Domain Routing. It is a technique for allocating IP addresses that boosts the effectiveness of address distribution. Super netting is another name for the system that supersedes the earlier one based on classes A, B, and C networks.

A single CIDR IP address can be used to provide numerous separate unique IP addresses.The only difference between a CIDR IP address and a regular IP address is that in CIDR, a slash is followed by a number at the end. For example, IP network prefix is the name of it.

CIDR Full Form

Characteristics of CIDR

It uses CIDR blocks to dynamically assign the IP addresses based on user requests and predefined rules. The CIDR block is assigned under the supervision of the Internet Assigned Number Authority (IANA).

IP addresses make up the CIDR block, which contains the following rules:

  • Each IP address assigned to a host must be continuous.
  • It is necessary for the block size to be a power 2 and to match the total number of IP addresses.
  • The block's first IP address must divide the block's size evenly.

Advantages of CIDR

  • With CIDR, addresses are allocated in sizes that are any binary multiple, providing efficient address space allocation.
  • The class imbalance is eliminated since there are no longer any class networks, allowing you to extensively utilise some areas of the address space while neglecting others.
  • Because of its effective routing entries feature, many networks can be represented by a small number of routing entries.
  • It incorporates the idea of subnetting within the internet itself, therefore no separate subnetting mechanism is necessary.
  • The network description is compiled and represented by a single entry.

Disadvantage of CIDR

The simplicity of the previous approach based on classes was its greatest advantage. You can tell how many bits of an IP address correspond to the network ID and how many to the host ID just by looking at the first octet. However, it is no longer feasible because CIDR's complexity is its fundamental flaw.

CIDR Notation

  • Without using conventional id address classes like Class, A, B, and C, we can assign an IP address to a host using CIDR.
  • We just specify the number of bits utilised for the network id in CIDR. Following the '/' symbol are the network id bits. For example, /10 indicates that 10 bits are used for the network id portion, leaving 32-10=22 bits for the host id portion.
  • Utilizing CIDR notation has the advantages of managing IP address space and reducing the number of entries in the routing table.

Uses of CIDR

  • Variable-length subnet masking serves as CIDR's basis (VLSM). It is now significantly more potent than the previous approach and can specify prefixes of any duration.
  • Two sets of numbers make up the CIDR IP addresses. Like how an IP address is expressed, the network address is written as a prefix (e.g.,
  • The suffix which expresses the address’s total number of bits (for example, /12) is the second element. When combined, a CIDR IP address will resemble something like this:
  • The network prefix is also defined in the IP address. The number of bits required determines these modifications.