Set a flag in the /dcim/interfaces/ to show that an address has been assigned

[bdlamprecht]

Issue type

[X] Feature request

Environment

• Python version: 3.6
• NetBox version: v2.3.0

Description

This came up in the NetworkToCode Slack channel today and while I have a basic understanding of why it isn't currently implemented, I'm just posing the question here just to see if it was at all possible and if so, what performance hits would occur.

The question came up when I discovered that you could see the relationship between address and interface at the endpoint /ipam/ip-address/, but not the other way around (i.e. no way to see if an interface even has an address assigned at /dcim/interfaces/).

What I'm trying to accomplish is to be able to look at /dcim/interfaces/ and immediately tell if I should use a Layer2 interface template (no assigned address) or a Layer3 interface template (an address IS assigned).

If there is an address, I don't even care it is, as I've already coded the logic to loop through the addresses assigned to a device.

Perhaps this is just a simple mind thinking out loud here, but wouldn't it be possible to set a flag on the /dcim/interfaces/ model when an address is assigned and then clear that flag if the address assignment was removed?

While I don't really understand the intricate details of the Django ORM, this example came up:

Joey Wilhelm [4:10 PM]
If you would like to add a `has_ipaddresses` boolean in the API, you would want to start with something like this:
>>> from django.db.models import Exists, OuterRef
>>> 
>>> from dcim.models import Interface
>>> from ipam.models import IPAddress
>>>
>>> ip_addresses = IPAddress.objects.filter(interface_id=OuterRef('pk'))
>>> interfaces = Interface.objects.annotate(has_ipaddresses=Exists(ip_addresses))

Thoughts one way or another?

[bdlamprecht]

I've been playing around with this some today and I think I may have found an alternative to setting a flag for when an IP address is assigned that wouldn't require any "penalties" due to primary-key and foreign-key lookups (pardon my terminology if it is not accurate).

As far as I can gather, the only instance where an interface carries specific vlans (access, tagged, tagged_all) AND has an IP address assigned is in the case of sub-interfaces. However, the current way to model that scenario within NetBox is to define each one separately (parent and child relationship are not tied together within NetBox).

If some type of check were created to ensure that interfaces can only be assigned VLANs OR IP addresses (similar to how you cannot have mode:access and tagged_vlans: { } at the same time), I believe this would work.

Can anyone think of why this would not be do-able?

[flycam]

If some type of check were created to ensure that interfaces can only be assigned VLANs OR IP addresses (similar to how you cannot have mode:access and tagged_vlans: { } at the same time), I believe this would work.

On Linux, it is possible to set an ip directly to an interface, and then also have tagged vlans on that interface as well.

[bdlamprecht]

Thanks for the information, that is interesting.

When you say something is impossible, leave it to Linux to prove otherwise. 😄