Iterating over all network interfaces in Ansible 2016-04-21

Description: Getting information about every network interface on a system with ansible is not that obvious. Here's the solution I found.

Reading Time: 1

Tags: Ansible DevOps

The problem

Ansible keeps a list of all network interfaces in the ansible_interfaces fact. Sometimes you need to iterate over all of these, but access the ansible_eth0 or other interface data, but doing so is non-obvious. Here’s what I found that works:

- name: debug print all interface ipv4 data
  when: "{{ hostvars[ansible_fqdn]['ansible_'~item]['ipv4'] is defined }}"
  debug:
     msg="{{ hostvars[ansible_fqdn]['ansible_'~item]['ipv4'] | pprint }}"
  with_items:
     - "{{ ansible_interfaces | map('replace', '-','_') | list }}"

Notes

• You can’t access the variables directly in facts, thus the use of hostvars to access the global facts, and ansible_fqdn to specify the current host.

• Per interface information is stored in ansible_eth0 or similar, thus the 'ansible_'~item which builds this interface name.

• Ansible facts don’t contain the - character but the interface name might, thus the map() filter that replaces them with _’s in with_items. The map filter returns a python generator, thus the call to list which converts the generator to a list.

• You may need to filter out any interfaces that might not be set up, which is done with the when: statement