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Some users are not accustomed to thinking of IP addresses in a bitwise fashion, so the hope here is to give enough of an introduction to that way of thinking for the reader to understand what the "newbits" and "netnum" arguments represent.
56 lines
1.8 KiB
Markdown
56 lines
1.8 KiB
Markdown
---
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layout: "functions"
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page_title: "cidrhost - Functions - Configuration Language"
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sidebar_current: "docs-funcs-ipnet-cidrhost"
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description: |-
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The cidrhost function calculates a full host IP address within a given
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IP network address prefix.
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---
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# `cidrhost` Function
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-> **Note:** This page is about Terraform 0.12 and later. For Terraform 0.11 and
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earlier, see
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[0.11 Configuration Language: Interpolation Syntax](../../configuration-0-11/interpolation.html).
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`cidrhost` calculates a full host IP address for a given host number within
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a given IP network address prefix.
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```hcl
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cidrhost(prefix, hostnum)
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```
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`prefix` must be given in CIDR notation, as defined in
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[RFC 4632 section 3.1](https://tools.ietf.org/html/rfc4632#section-3.1).
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`hostnum` is a whole number that can be represented as a binary integer with
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no more than the number of digits remaining in the address after the given
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prefix. For more details on how this function interprets CIDR prefixes and
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populates host numbers, see the worked example for
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[`cidrsubnet`](./cidrsubnet.html).
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Conventionally host number zero is used to represent the address of the
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network itself and the host number that would fill all the host bits with
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binary 1 represents the network's broadcast address. These numbers should
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generally not be used to identify individual hosts except in unusual
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situations, such as point-to-point links.
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This function accepts both IPv6 and IPv4 prefixes, and the result always uses
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the same addressing scheme as the given prefix.
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## Examples
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```
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> cidrhost("10.12.127.0/20", 16)
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10.12.112.16
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> cidrhost("10.12.127.0/20", 268)
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10.12.113.12
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> cidrhost("fd00:fd12:3456:7890:00a2::/72", 34)
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fd00:fd12:3456:7890::22
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```
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## Related Functions
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* [`cidrsubnet`](./cidrsubnet.html) calculates a subnet address under a given
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network address prefix.
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