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functions cidrsubnet function docs-funcs-ipnet-cidrsubnet The cidrsubnet function calculates a subnet address within a given IP network address prefix.

cidrsubnet Function

cidrsubnet calculates a subnet address within given IP network address prefix.

cidrsubnet(prefix, newbits, netnum)

prefix must be given in CIDR notation, as defined in RFC 4632 section 3.1.

newbits is the number of additional bits with which to extend the prefix. For example, if given a prefix ending in /16 and a newbits value of 4, the resulting subnet address will have length /20.

netnum is a whole number that can be represented as a binary integer with no more than newbits binary digits, which will be used to populate the additional bits added to the prefix.

This function accepts both IPv6 and IPv4 prefixes, and the result always uses the same addressing scheme as the given prefix.

Examples

> cidrsubnet("172.16.0.0/12", 4, 2)
172.18.0.0/16
> cidrsubnet("10.1.2.0/24", 4, 15)
10.1.2.240/28
> cidrsubnet("fd00:fd12:3456:7890::/56", 16, 162)
fd00:fd12:3456:7800:a200::/72

Related Functions

  • cidrhost calculates the IP address for a single host within a given network address prefix.
  • cidrnetmask converts an IPv4 network prefix in CIDR notation into netmask notation.