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

     1  ---
     2  layout: "functions"
     3  page_title: "cidrnetmask - Functions - Configuration Language"
     4  sidebar_current: "docs-funcs-ipnet-cidrnetmask"
     5  description: |-
     6    The cidrnetmask function converts an IPv4 address prefix given in CIDR
     7    notation into a subnet mask address.
     8  ---
     9  
    10  # `cidrnetmask` 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  `cidrnetmask` converts an IPv4 address prefix given in CIDR notation into
    17  a subnet mask address.
    18  
    19  ```hcl
    20  cidrnetmask(prefix)
    21  ```
    22  
    23  `prefix` must be given in IPv4 CIDR notation, as defined in
    24  [RFC 4632 section 3.1](https://tools.ietf.org/html/rfc4632#section-3.1).
    25  
    26  The result is a subnet address formatted in the conventional dotted-decimal
    27  IPv4 address syntax, as expected by some software.
    28  
    29  CIDR notation is the only valid notation for IPv6 addresses, so `cidrnetmask`
    30  produces an error if given an IPv6 address.
    31  
    32  ## Examples
    33  
    34  ```
    35  > cidrnetmask("172.16.0.0/12")
    36  255.240.0.0
    37  ```