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Details on how to convert subnet masks into CIDR

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Use data reported by Ansible network facts as an example.
This commit is contained in:
Stig Telfer 2016-01-27 12:02:59 +00:00
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commit 326ae21089
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docsite/rst/playbooks_filters_ipaddr.rst
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@ -283,6 +283,37 @@ If needed, you can extract subnet and prefix information from 'host/prefix' valu
# {{ host_prefix | ipaddr('host/prefix') | ipaddr('prefix') }}
[64, 24]
Converting subnet masks to CIDR notation
----------------------------------------
Given a subnet in the form of network address and subnet mask, it can be converted into CIDR notation using ``ipaddr()``. This can be useful for converting Ansible facts gathered about network configuration from subnet masks into CIDR format::
ansible_default_ipv4: {
address: "192.168.0.11",
alias: "eth0",
broadcast: "192.168.0.255",
gateway: "192.168.0.1",
interface: "eth0",
macaddress: "fa:16:3e:c4:bd:89",
mtu: 1500,
netmask: "255.255.255.0",
network: "192.168.0.0",
type: "ether"
}
First concatenate network and netmask::
net_mask = "{{ ansible_default_ipv4.network }}/{{ ansible_default_ipv4.netmask }}"
'192.168.0.0/255.255.255.0'
This result can be canonicalised with ``ipaddr()`` to produce a subnet in CIDR format::
# {{ net_mask | ipaddr('prefix') }}
'24'
# {{ net_mask | ipaddr('net') }}
'192.168.0.0/24'
IP address conversion
---------------------