ansible - add 1 to ip address variable using ipmath

Question

This seems like it should be fairly straightforward. I have a variable I defined in default.yml that I'd like to increment by one:

start_ip: 10.10.10.10

Then I set the fact and report it:

- set_fact:
    repo_ip:  "{{ start_ip|ipmath(1) }}"

- debug:
   msg: "repo_ip is {{ repo_ip }}"

I've also tried:

 - set_fact:
       repo_ip:  "{{ start_ip }}|ipmath(1)"

with the same result:

repo_ip is 10.10.10.10|ipmath(1)

Of course what I want is 10.10.10.11. What am I doing incorrectly?

Answer 1

Actually, it should work as written in your first example. The second one is wrong, obviously, as the filter only works if inside the curly braces.

    - hosts: localhost
  gather_facts: false
  connection: local
  vars:
    start_ip: 10.10.10.10

  tasks:
    - set_fact:
        next_ip: "{{ start_ip|ipmath(1) }}"
    - debug:
        msg: "Next ip of {{ start_ip }} is: {{ next_ip }}"

This returns what you wanted.

PLAY [localhost] ***************************************************************

TASK [set_fact] ****************************************************************
ok: [localhost]

TASK [debug] *******************************************************************
ok: [localhost] => {
    "msg": "Next ip of 10.10.10.10 is: 10.10.10.11"
}