49 lines
1.4 KiB
Markdown
49 lines
1.4 KiB
Markdown
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---
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layout: "functions"
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page_title: "cidrsubnet function"
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sidebar_current: "docs-funcs-ipnet-cidrsubnet"
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description: |-
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The cidrsubnet function calculates a subnet address within a given IP network
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address prefix.
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---
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# `cidrsubnet` Function
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`cidrhost` calculates a subnet address within given IP network address prefix.
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```hcl
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cidrsubnet(prefix, newbits, netnum)
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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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`newbits` is the number of additional bits with which to extend the prefix.
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For example, if given a prefix ending in `/16` and a `newbits` value of
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`4`, the resulting subnet address will have length `/20`.
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`netnum` is a whole number that can be represented as a binary integer with
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no more than `newbits` binary digits, which will be used to populate the
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additional bits added to the prefix.
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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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> cidrsubnet("172.16.0.0/12", 4, 2)
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172.18.0.0/16
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> cidrsubnet("10.1.2.0/24", 4, 15)
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10.1.2.240/28
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> cidrsubnet("fd00:fd12:3456:7890::/56", 16, 162)
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fd00:fd12:3456:7800:a200::/72
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```
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## Related Functions
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* [`cidrhost`](./cidrhost.html) calculates the IP address for a single host
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within a given network address prefix.
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* [`cidrnetmask`](./cidrnetmask.html) converts an IPv4 network prefix in CIDR
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notation into netmask notation.
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