Hi 👋

It’s the VLAN ID for the sub-interface which ansible_facts is showing for
eth0_1


You must use the iproute 2 package with ip addr not net-tools


If you want to modify this then you will need set_facts magic;


To access variables of other hosts, you should enable fact caching
<http://docs.ansible.com/ansible/playbooks_variables.html#fact-caching>.


In playbook files, you should add in:

gather_facts: True

#to update facts.


The ansible_interfaces fact lists all of the existing network interfaces.


Some hints to get an interface when you know more information:


    var:

      allNetworkInterfaces: "{{ ansible_facts | dict2items |
selectattr('value.ipv4', 'defined') | map(attribute='value') | list }}"

      allNetworkInterfaces_variant2: "{{ ansible_facts.interfaces |
map('extract', ansible_facts ) | list }}"

      interfaceWithKnownIp: "{{ ansible_facts | dict2items |
selectattr('value.ipv4', 'defined') | selectattr('value.ipv4.address',
'equalto', myKnowIpV4) | first }}"

      interfaceWithKnownIp_fromVar: "{{ allNetworkInterfaces |
selectattr('ipv4.address', 'equalto', myKnowIpV4) | first }}"

      interfacesWithPartialKnowMac: "{{ allNetworkInterfaces |
selectattr('macaddress', 'match', knownMacPrefix~'.*') | list }}"

      interfacesWitKnowType: "{{ allNetworkInterfaces | selectattr('type',
'equalto', knownType) | sort(attribute='device') | list }}"

      # extended on 2020-10-28

      queryForKnownIpv6: "[*].{device: device, ipv4: ipv4, ipv6: ipv6[?
address == 'fe80::a00:27ff:fe38:ad36']}[?ipv6])" # string must be in ' #
sorry, only partial interface info, did not find out how to return all info
directly

      interfacesWithKnownIpv6: '{{ allNetworkInterfaces |
json_query(queryForKnownIpv6) | first }}'

      queryForKnownIpv4_linux: "[?ipv4.address == '{{ myKnownIpV4
}}']}[?ipv4])" # string must be in '

      interfacesWithKnownIp_variantJsonQuery: '{{ allNetworkInterfaces |
json_query(queryForKnownIpv4_linux) | first }}'

some short explications:



   - dict2item
   
<https://docs.ansible.com/ansible/latest/user_guide/playbooks_filters.html#dict-filter>
    because selectattr
   <http://jinja.pocoo.org/docs/dev/templates/#selectattr> expects an array
   - map(attribute='...') <http://jinja.pocoo.org/docs/dev/templates/#map> to
   unpack this array
   - map('extract', ...)
   
<https://docs.ansible.com/ansible/latest/user_guide/playbooks_filters.html#extracting-values-from-containers>
to
   extract interfaces from ansible_facts
   - ansible_facts.interfaces is the same as ansible_interfaces
   - json_query()
   
<https://docs.ansible.com/ansible/latest/user_guide/playbooks_filters.html#selecting-json-data-json-queries>
for
   flexible selecting and unpacking, an alternative variant with `map()? is
   welcome


the ansible_interfaces fact contains a list of all the network interfaces
and they appear to be in order (i.e., the first ethernet interface would
have been called eth0, the second eth1, etc). With a little set_fact magic:


- name: define traditional ethernet facts

  set_fact:

    ansible_eth: "{% set ansible_eth = ansible_eth|default([]) +
[hostvars[inventory_hostname]['ansible_' + item]] %}{{ ansible_eth|list }}"

  when: hostvars[inventory_hostname]['ansible_' + item]['type'] == 'ether'

  with_items:

    - "{{ hostvars[inventory_hostname]['ansible_interfaces'] }}"

This loops over all of the ansible_interfaces entries for the current
machine and builds a list of the hostvars[inventory_hostname]['ansible_' +
item] entries that have a type equal to "ether".

Thus now ansible_eth.0 and ansible_eth.1 should be roughly equivalent to
the old ansible_eth0 and ansible_eth1 respectively.


Best,

S.W

On Thu, 12 Jan 2023 at 11:24, Kathy L <[email protected]> wrote:

> I'm using ansible-core 1.18.  When I gather facts on a device, it shows
> the interfaces of eth0, eth0_1, eth1 and lo. The results of "ip a" show
> only eth0, eth1 and lo interfaces .  When I try to start arpwatch for each
> interface (other than lo), it fails on eth0_1, which makes sense to me.
> Why does ansible_facts interfaces show eth0_1?
>
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