Ansible: How to increment IP address?

Question

I am passing a variable to Ansible with --extra-vars "lan=10.10.10.1".

I now need to increment this IPaddress so that the last octet is .2 so it will equal 10.10.10.2.

How would this be achieved in Ansible?

Answer 1

In one line:

- set_fact: new_ip="{{ lan | regex_replace('(^.*\.).*$', '\\1') }}{{lan.split('.')[3] | int + 1 }}"

How does it work?

  tasks:
  - name: Echo the passed IP
    debug: var={{lan}}

  - name: Extract the last octet, increment it and store it
    set_fact: octet={{lan.split('.')[3] | int + 1 }}
  - debug: var=octet

  - name: Append the incremented octet to the first 3 octets
    set_fact: new_ip="{{ lan | regex_replace('(^.*\.).*$', '\\1') }}{{octet}}"
  - debug: var=new_ip

Output

TASK: [Echo the passed IP] ****************************************************
ok: [127.0.0.1] => {
    "127.0.0.1": "{{ 127.0.0.1 }}"
}
TASK: [Extract the last octet, increment it and store it] *********************
ok: [127.0.0.1] => {"ansible_facts": {"octet": "2"}}

TASK: [debug var=octet] *******************************************************
ok: [127.0.0.1] => {
    "octet": "2"
}
TASK: [Append the incremented octet to the first 3 octets] ********************
ok: [127.0.0.1] => {"ansible_facts": {"new_ip": "127.0.0.2"}}

TASK: [debug var=new_ip] ******************************************************
ok: [127.0.0.1] => {
    "new_ip": "127.0.0.2"
}