github.com/rstandt/terraform@v0.12.32-0.20230710220336-b1063613405c/website/docs/configuration/functions/cidrhost.html.md (about)

     1  ---
     2  layout: "functions"
     3  page_title: "cidrhost - Functions - Configuration Language"
     4  sidebar_current: "docs-funcs-ipnet-cidrhost"
     5  description: |-
     6    The cidrhost function calculates a full host IP address within a given
     7    IP network address prefix.
     8  ---
     9  
    10  # `cidrhost` Function
    11  
    12  -> **Note:** This page is about Terraform 0.12 and later. For Terraform 0.11 and
    13  earlier, see
    14  [0.11 Configuration Language: Interpolation Syntax](../../configuration-0-11/interpolation.html).
    15  
    16  `cidrhost` calculates a full host IP address for a given host number within
    17  a given IP network address prefix.
    18  
    19  ```hcl
    20  cidrhost(prefix, hostnum)
    21  ```
    22  
    23  `prefix` must be given in CIDR notation, as defined in
    24  [RFC 4632 section 3.1](https://tools.ietf.org/html/rfc4632#section-3.1).
    25  
    26  `hostnum` is a whole number that can be represented as a binary integer with
    27  no more than the number of digits remaining in the address after the given
    28  prefix. For more details on how this function interprets CIDR prefixes and
    29  populates host numbers, see the worked example for
    30  [`cidrsubnet`](./cidrsubnet.html).
    31  
    32  Conventionally host number zero is used to represent the address of the
    33  network itself and the host number that would fill all the host bits with
    34  binary 1 represents the network's broadcast address. These numbers should
    35  generally not be used to identify individual hosts except in unusual
    36  situations, such as point-to-point links.
    37  
    38  This function accepts both IPv6 and IPv4 prefixes, and the result always uses
    39  the same addressing scheme as the given prefix.
    40  
    41  ## Examples
    42  
    43  ```
    44  > cidrhost("10.12.127.0/20", 16)
    45  10.12.112.16
    46  > cidrhost("10.12.127.0/20", 268)
    47  10.12.113.12
    48  > cidrhost("fd00:fd12:3456:7890:00a2::/72", 34)
    49  fd00:fd12:3456:7890::22
    50  ```
    51  
    52  ## Related Functions
    53  
    54  * [`cidrsubnet`](./cidrsubnet.html) calculates a subnet address under a given
    55    network address prefix.