In my day job, I’m using Ansible to provision networks in OpenStack. One of the complaints I’ve had about the way I now define them is that the person implementing the network has to spell out all the network elements – the subnet size, DHCP pool, the addresses of the firewalls and names of those items. This works for a manual implementation process, but is seriously broken when you try to hand that over to someone else to implement. Most people just want something which says “Here is the network I want to implement – 192.0.2.0/24″… and let the system make it for you.
So, I wrote some code to make that happen. It’s not perfect, and it’s not what’s in production (we have lots more things I need to add for that!) but it should do OK with an IPv4 network.
Hope this makes sense!
---
- hosts: localhost
vars:
- networks:
# Defined as a subnet with specific router and firewall addressing
external:
subnet: "192.0.2.0/24"
firewall: "192.0.2.1"
router: "192.0.2.254"
# Defined as an IP address and CIDR prefix, rather than a proper network address and CIDR prefix
internal_1:
subnet: "198.51.100.64/24"
# A valid smaller network and CIDR prefix
internal_2:
subnet: "203.0.113.0/27"
# A tiny CIDR network
internal_3:
subnet: "203.0.113.64/30"
# These two CIDR networks are unusable for this environment
internal_4:
subnet: "203.0.113.128/31"
internal_5:
subnet: "203.0.113.192/32"
# A massive CIDR network
internal_6:
subnet: "10.0.0.0/8"
tasks:
# Based on https://stackoverflow.com/a/47631963/5738 with serious help from mgedmin and apollo13 via #ansible on Freenode
- name: Add router and firewall addressing for CIDR prefixes < 30
set_fact:
networks: >
{{ networks | default({}) | combine(
{item.key: {
'subnet': item.value.subnet | ipv4('network'),
'router': item.value.router | default((( item.value.subnet | ipv4('network') | ipv4('int') ) + 1) | ipv4),
'firewall': item.value.firewall | default((( item.value.subnet | ipv4('broadcast') | ipv4('int') ) - 1) | ipv4),
'dhcp_start': item.value.dhcp_start | default((( item.value.subnet | ipv4('network') | ipv4('int') ) + 2) | ipv4),
'dhcp_end': item.value.dhcp_end | default((( item.value.subnet | ipv4('broadcast') | ipv4('int') ) - 2) | ipv4)
}
}) }}
with_dict: "{{ networks }}"
when: item.value.subnet | ipv4('prefix') < 30
- name: Add router and firewall addressing for CIDR prefixes = 30
set_fact:
networks: >
{{ networks | default({}) | combine(
{item.key: {
'subnet': item.value.subnet | ipv4('network'),
'router': item.value.router | default((( item.value.subnet | ipv4('network') | ipv4('int') ) + 1) | ipv4),
'firewall': item.value.firewall | default((( item.value.subnet | ipv4('broadcast') | ipv4('int') ) - 1) | ipv4)
}
}) }}
with_dict: "{{ networks }}"
when: item.value.subnet | ipv4('prefix') == 30
- debug:
var: networks
