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  • About IPV6 CIDR to Range Calculator

    IPv6 CIDR to Range Calculator converts the given IPv6 CIDR to its range parameters. The range parameters include First IP, Last IP, Block Size of a given range, and more. This tool instantly converts the given IPv6 CIDR to its range parameters. Example format for calculation is 2001:4860:4860::8888/32

    What is CIDR?

    CIDR stands for Classless Inter-Domain Routing (also known as supernetting), which assigns the Internet Protocol (IP) addresses that improve the efficiency of address distribution and replace the old system based on Class A Class B, and Class C networks.

    The CIDR came with two initial goals.

    1. To slow down the increase of routing tables on routers across the network.
    2. Decrease the rapid consumption or exhaustion of IPv4 addresses.

    Because of that, the number of available internet addresses has significantly increased.

    Development of CIDR

    With the development of the Domain Name System (DNS), the classful method was designed to distribute IP addresses. But the original classful network design contained some inefficiencies that drained the pool of unassigned IP addresses faster than expected. The classful routing system included the following.

    • Class A, with an 8-bit network address and 24-bit host address, and over 16 million IP addresses.
    • Class B, with a 16-bit network address and 16-bit host address, and with 65,535 IP addresses.
    • Class C, with a 24-bit network address and 8-bit host address, and with 254 IP addresses.

    You can quickly tell to what address class an IP address belongs to just by looking at it.

    • If the first bit of an IP address is a zero, it refers to a class A network.
    • If the first bits are one, zero, it refers to a class B network.
    • If the first bits are 110, it refers to a class C network.

    However, the real problem occurred in the classful routing system when an organization needed more than 254 host identifiers.

    Suppose a company required more than 254 IP addresses. It would be switched to a Class B license. However, in that case, more than 60,000 IP addresses would remain unused if a company did not need them. That would result in the exhaustion of the available IP addresses. To overcome that issue, Internet Engineering Task Force (IETF) introduced the CIDR in 1993.

    How does CIDR work?

    Classless Inter-Domain Routing (CIDR) is based on variable-length subnet masking (VLSM), allowing network engineers to distribute an IP address space into a hierarchy of subnets of varying sizes. Therefore, it makes it possible to create subnetworks with varying host counts without wasting large numbers of IP addresses.

    The CIDR IP addresses are made up of two sets of numbers.

    1. A prefix, the binary representation of the network address, just like a standard IP address
    2. A suffix indicates the total number of bits in the network address.

    Putting it together, a CIDR notation may look like: Here, the first 17 bits are the network part of the address, while the last 15 bits are for host addresses.

    IPv4 addresses are 32-bits long. You can apply the same CIDR notation rule to IPv6 addresses. The only difference is that IPv6 addresses can contain up to 128-bits.

    CIDR blocks

    CIDR blocks are IP addresses that share the same prefix and the same number of bits. The length of the prefix determines the size of CIDR blocks. The short prefix allows more addresses, thus making a more significant block. While the larger prefix represents fewer addresses, it makes a small block.

    Internet Assigned Numbers Authority (IANA) initially controls the blocks. IANA is responsible for distributing large IP addresses blocks to Regional Internet Registries (RIRs).

    CIDR notation

    On subnetting, we relied on Network ID, Subnet ID, and Host ID. However, in CIDR, the Network IP and Subnet ID are merged into one. In CIDR, we get that slash notation (/). This slash notation is called CIDR notation. CIDR rejects the concept of address classes completely, allowing an address to be defined by only two Individual IDs.

    IPv6 CIDR to Range Calculator

    CIDR reduces the wasting of IP addresses without creating an outburst in the number of entries in a routing table. It's now a backbone of routing systems on the internet.

    The CIDR notation is also used for the IPv6 addresses with the same syntax. The only difference between IPv4 and IPv6 is that IPv4 is 32-bits long, and IPv6 is 128 bits long.

    To utilize the IPv6 CIDR calculator. Perform the following steps.

    • Open the tool: IPv6 Subnet Calculator - IPv6 CIDR to Range Calculator.
    • Enter the IPv6 CIDR. As a sample, enter the following CIDR IPv6 address 2001:4860:4860::8888/32
    • The tool calculates the IPv6 address range based on the IPv6 CIDR and displays the first and last IPv6 address in the subnet mask range, the number of IPv6 addresses in the block, IPv6 CIDR, and prefix length.

    You can also convert the given IPv6 Ranges to their corresponding CIDR by using the IPv6 Range to CIDR Calculator.