github.com/iaas-resource-provision/iaas-rpc@v1.0.7-0.20211021023331-ed21f798c408/website/docs/language/functions/cidrsubnets.html.md (about)

     1  ---
     2  layout: "language"
     3  page_title: "cidrsubnets - Functions - Configuration Language"
     4  sidebar_current: "docs-funcs-ipnet-cidrsubnets"
     5  description: |-
     6    The cidrsubnets function calculates a sequence of consecutive IP address
     7    ranges within a particular CIDR prefix.
     8  ---
     9  
    10  # `cidrsubnets` Function
    11  
    12  `cidrsubnets` calculates a sequence of consecutive IP address ranges within
    13  a particular CIDR prefix.
    14  
    15  ```hcl
    16  cidrsubnets(prefix, newbits...)
    17  ```
    18  
    19  `prefix` must be given in CIDR notation, as defined in
    20  [RFC 4632 section 3.1](https://tools.ietf.org/html/rfc4632#section-3.1).
    21  
    22  The remaining arguments, indicated as `newbits` above, each specify the number
    23  of additional network prefix bits for one returned address range. The return
    24  value is therefore a list with one element per `newbits` argument, each
    25  a string containing an address range in CIDR notation.
    26  
    27  For more information on IP addressing concepts, see the documentation for the
    28  related function [`cidrsubnet`](./cidrsubnet.html). `cidrsubnet` calculates
    29  a single subnet address within a prefix while allowing you to specify its
    30  subnet number, while `cidrsubnets` can calculate many at once, potentially of
    31  different sizes, and assigns subnet numbers automatically.
    32  
    33  When using this function to partition an address space as part of a network
    34  address plan, you must not change any of the existing arguments once network
    35  addresses have been assigned to real infrastructure, or else later address
    36  assignments will be invalidated. However, you _can_ append new arguments to
    37  existing calls safely, as long as there is sufficient address space available.
    38  
    39  This function accepts both IPv6 and IPv4 prefixes, and the result always uses
    40  the same addressing scheme as the given prefix.
    41  
    42  -> **Note:** [The Terraform module `hashicorp/subnets/cidr`](https://registry.terraform.io/modules/hashicorp/subnets/cidr)
    43  wraps `cidrsubnets` to provide additional functionality for assigning symbolic
    44  names to your networks and skipping prefixes for obsolete allocations. Its
    45  documentation includes usage examples for several popular cloud virtual network
    46  platforms.
    47  
    48  ## Examples
    49  
    50  ```
    51  > cidrsubnets("10.1.0.0/16", 4, 4, 8, 4)
    52  [
    53    "10.1.0.0/20",
    54    "10.1.16.0/20",
    55    "10.1.32.0/24",
    56    "10.1.48.0/20",
    57  ]
    58  
    59  > cidrsubnets("fd00:fd12:3456:7890::/56", 16, 16, 16, 32)
    60  [
    61    "fd00:fd12:3456:7800::/72",
    62    "fd00:fd12:3456:7800:100::/72",
    63    "fd00:fd12:3456:7800:200::/72",
    64    "fd00:fd12:3456:7800:300::/88",
    65  ]
    66  ```
    67  
    68  You can use nested `cidrsubnets` calls with
    69  [`for` expressions](/docs/language/expressions/for.html)
    70  to concisely allocate groups of network address blocks:
    71  
    72  ```
    73  > [for cidr_block in cidrsubnets("10.0.0.0/8", 8, 8, 8, 8) : cidrsubnets(cidr_block, 4, 4)]
    74  [
    75    [
    76      "10.0.0.0/20",
    77      "10.0.16.0/20",
    78    ],
    79    [
    80      "10.1.0.0/20",
    81      "10.1.16.0/20",
    82    ],
    83    [
    84      "10.2.0.0/20",
    85      "10.2.16.0/20",
    86    ],
    87    [
    88      "10.3.0.0/20",
    89      "10.3.16.0/20",
    90    ],
    91  ]
    92  ```
    93  
    94  ## Related Functions
    95  
    96  * [`cidrhost`](./cidrhost.html) calculates the IP address for a single host
    97    within a given network address prefix.
    98  * [`cidrnetmask`](./cidrnetmask.html) converts an IPv4 network prefix in CIDR
    99    notation into netmask notation.
   100  * [`cidrsubnet`](./cidrsubnet.html) calculates a single subnet address, allowing
   101    you to specify its network number.