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Mastering CIDRs With Azure Bicep

· 2 min read
Luke Murray
Luke Murray
Author

Classless Inter-Domain Routing (CIDR) is a method of allocating IP addresses and routing Internet Protocol (IP) packets.

Mastering CIDRs With Azure Bicep

This article includes sample Bicep functions for working with CIDR, for Azure Virtual Network and Subnet creation.

CiDR.bicep
    // This function parses the CIDR notation and returns an object with the network address, subnet mask, and other details.
    output v6addressspace object = parseCidr('2001:db8:1234::/48')

    // This function generates an array of subnets within the specified CIDR block. The subnet size is 64, and the index calculates the subnet.
    // The 'range(0, 5)' function generates an array of numbers from 0 to 4. The 'for' loop iterates over these numbers.
    // For each number 'i', the 'cidrSubnet' function calculates a subnet within the '2001:db8:1234::/48' CIDR block.
    // The subnet size is 64, and 'i' is used as the index. The resulting array contains the calculated subnets.
    output v6subnets array = [for i in range(0, 5): cidrSubnet('2001:db8:1234::/48', 64, i)]

    // This function generates an array of host addresses within the specified CIDR block. The index is used to calculate the host address.
    // Similar to the 'v6subnets' array, the 'range(0, 5)' function generates an array of numbers from 0 to 4.
    // For each number 'i', the 'cidrHost' function calculates a host address within the '2001:db8:1234::/48' CIDR block.
    // The resulting array contains the calculated host addresses.
    output v6hosts array = [for i in range(0, 5): cidrHost('2001:db8:1234::/48', i)]

    // This function generates a string within the specified CIDR block. The host index is always 3 (Azure Reserved).
    // The 'cidrHost' function calculates a host address within the '2001:db8:1234::/48' CIDR block.
    // The host index is '0 + 3', which is 3. This is because the first three addresses in a subnet are reserved in Azure.
    output v6hostsazure string = cidrHost('2001:db8:1234::/48', 0 + 3)

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