CIDR

Definition

CIDR, or Classless Inter-Domain Routing, is a method for allocating IP addresses and routing internet traffic more efficiently than the traditional classful addressing system. This approach allows for the aggregation of multiple IP addresses into a single routing table entry, reducing the size of routing tables and improving overall internet performance. CIDR also allows network administrators to create subnets of varying sizes, enhancing the flexibility in managing IP address assignments.

5 Must Know Facts For Your Next Test

1. CIDR was introduced in 1993 to replace the older classful addressing scheme, which was inefficient and led to rapid depletion of available IP addresses.
2. CIDR notation uses a slash (/) followed by a number to denote the number of bits in the subnet mask, such as 192.168.1.0/24, indicating 24 bits for the network part and 8 bits for hosts.
3. CIDR allows for supernetting, which is the practice of combining multiple contiguous networks into a larger address block to simplify routing.
4. The implementation of CIDR has significantly reduced the size of routing tables across the internet, helping to alleviate the strain on routers and improve routing efficiency.
5. CIDR is crucial for IPv4 address conservation and is widely used in both IPv4 and IPv6 addressing schemes to manage IP space effectively.

Review Questions

• How does CIDR improve upon the traditional classful addressing system in terms of IP address allocation?
  • CIDR improves upon classful addressing by allowing for more flexible allocation of IP addresses, enabling network administrators to assign varying sizes of subnets based on actual needs rather than fixed classes. This leads to more efficient use of available IP address space and helps prevent wastage. Additionally, CIDR supports aggregation, which reduces the number of entries in routing tables and streamlines internet routing.
• Discuss the impact of CIDR on routing tables and overall internet performance.
  • CIDR has significantly reduced the size of routing tables by allowing multiple networks to be represented by a single entry through address aggregation. This simplification helps routers manage routes more efficiently and minimizes the processing overhead involved in routing decisions. Consequently, overall internet performance improves due to faster packet forwarding and decreased latency in route lookups.
• Evaluate how CIDR addresses the challenges posed by IPv4 address depletion and its implications for future internet growth.
  • CIDR plays a critical role in addressing IPv4 address depletion by optimizing how IP addresses are allocated and managed. By allowing for variable-length subnet masks and supernetting, CIDR maximizes the efficient use of existing address space, delaying the exhaustion of IPv4 addresses. As internet growth continues, CIDR's strategies will be essential for transitioning to IPv6, ensuring scalability while accommodating an ever-increasing number of devices online.

Related terms

Subnetting: The process of dividing a larger IP network into smaller, more manageable sub-networks, which helps optimize the use of IP addresses.

Routing Table: A data structure used by routers to determine the best path for forwarding packets through the network.

IP Address:

A unique string of numbers separated by periods that identifies each computer using the Internet Protocol to communicate over a network.