How to Use the Command 'cidr' (with Examples)
The ‘cidr’ command is a versatile tool designed to streamline and simplify the management of IPv4 and IPv6 CIDR (Classless Inter-Domain Routing) network prefixes. This command offers various functionalities, such as counting the total number of addresses within a CIDR range, checking if an address belongs to a CIDR range, explaining the characteristics of a CIDR range, identifying overlaps between two CIDR ranges, and subdividing a CIDR range into multiple smaller networks. This command-line utility is particularly useful for network administrators and IT professionals who frequently engage in IP address planning and management.
Use case 1: Explain a CIDR range
Code:
cidr explain 10.0.0.0/16
Motivation:
When managing a network, understanding the properties of a given CIDR range is crucial. Explaining a CIDR range helps network administrators gain insights into the address space, including the network size and address bounds. It aids in effective planning and organization of the network infrastructure.
Explanation:
cidr explain: This portion of the command tells the ‘cidr’ tool to provide details about a specified CIDR range.10.0.0.0/16: This argument represents the target CIDR range to be explained. “10.0.0.0” is the starting IP address, and “/16” signifies that the first 16 bits of the IP address constitute the network prefix, defining the network size and coverage.
Example Output:
CIDR: 10.0.0.0/16
IP Range: 10.0.0.0 - 10.0.255.255
Network Address: 10.0.0.0
Broadcast Address: 10.0.255.255
Number of addresses: 65536
Use case 2: Check whether an address belongs to a CIDR range
Code:
cidr contains 10.0.0.0/16 10.0.14.5
Motivation:
Network administrators often need to verify if particular IP addresses reside within a given subnet. Checking whether an address belongs to a CIDR range is essential for access control, routing decisions, and network diagnostics.
Explanation:
cidr contains: This component of the command instructs the ‘cidr’ tool to check if a specific IP address fits within the defined CIDR range.10.0.0.0/16: Specifies the CIDR range under examination.10.0.14.5: Represents the specific IP address for which presence within the CIDR range is being checked.
Example Output:
10.0.14.5 is within 10.0.0.0/16
Use case 3: Get a count of all addresses in a CIDR range
Code:
cidr count 10.0.0.0/16
Motivation:
Knowing how many IP addresses a CIDR block encompasses is vital for capacity planning and resource allocation. This information is useful when deciding whether a given block is sufficiently large for a project or if it necessitates subdivision.
Explanation:
cidr count: Commands the ‘cidr’ tool to provide the total number of possible IP addresses within a specified CIDR range.10.0.0.0/16: The CIDR range for which the total number of addresses is calculated.
Example Output:
65536
Use case 4: Check whether two CIDR ranges overlap
Code:
cidr overlaps 10.0.0.0/16 10.0.14.0/22
Motivation:
When designing or integrating networks, ensuring that different network segments do not accidentally overlap is key to avoiding routing conflicts and ensuring seamless network performance. Checking for overlapping CIDR ranges prevents unintended interactions between network segments.
Explanation:
cidr overlaps: Directs the ‘cidr’ tool to check if two CIDR blocks share any common IP addresses.10.0.0.0/16and10.0.14.0/22: These are the two CIDR blocks under investigation for overlap.
Example Output:
These CIDR ranges overlap.
Use case 5: Divide a CIDR range into a specific number of networks
Code:
cidr divide 10.0.0.0/16 9
Motivation:
Dividing a CIDR range into multiple subnets is often necessary when organizing a network to support various departments, locations, or services within a larger system. This functionality simplifies network segmentation and enhances management efficiency.
Explanation:
cidr divide: Commands the ‘cidr’ utility to partition a given CIDR block into a specified number of smaller networks.10.0.0.0/16: The target CIDR range to be subdivided.9: The overall number of subdivisions desired.
Example Output:
10.0.0.0/19
10.0.32.0/19
10.0.64.0/19
10.0.96.0/19
10.0.128.0/19
10.0.160.0/19
10.0.192.0/19
10.0.224.0/21
10.0.232.0/21
Conclusion:
The ‘cidr’ command proves itself to be an indispensable utility for network administrators by offering concise solutions for managing CIDR network prefixes. Whether explaining CIDR blocks, validating IP address containment, evaluating overlaps, counting potential IP addresses, or subdividing within networks, this tool exemplifies simplicity and efficiency in network management tasks. By mastering these commands, professionals can ensure more effective, conflict-free network planning and operation.
