Netbox custom script: how do I retrieve existing VLAN object which shall be added to a new Prefix?

[jesper-munk2]

In my custom script I create a new site with switches etc and also to prefixes.
In my code below I attempt to create two prefixes for my site.
For prefix iot_prefix, where I just add the prefix without any additional attributes, I succeed.
For prefix corporate_vlan, where I attempt to add attribute vlan, if fails. I want to add existing VLAN id 2099, name corporate.
However my code line corporate_vlan = VLAN.objects.filter(vid_gt="2099") does not return a valid VLAN object. The same applies when I use attribute filter iname_contains="corporate".

How do I get the VLAN object VLAN id 2099, name corporate, such that I can add that attribute to my corporate_prefix, when I create that.

Generate Prefixes for site

    corporate_vlan = VLAN.objects.filter(vid_gt="2099")  # Already defined in Netbox
    self.log_success(f"corporate_vlan object {corporate_vlan}")
    self.log_success(pprint.pformat(corporate_vlan))
    corporate_prefix = Prefix.objects.create(
        prefix=data["corporate_ipsubnet"],
        scope=site,            
        vlan=corporate_vlan)
    self.log_success(f"Created Prefix {corporate_prefix} for site {site}")
    iot_prefix = Prefix.objects.create(
        prefix=data["iot_ipsubnet"],
        scope=site,)
    self.log_success(f"Created Prefix {iot_prefix} for site {site}")

[pheus]

Hi,

NetBox uses Django as its framework, so the Django ORM documentation is a good reference here.

The main issue is that VLAN.objects.filter(...) returns a QuerySet, even if it only contains one VLAN. The vlan field on Prefix expects a single VLAN object, so you should retrieve exactly one object instead:

corporate_vlan = VLAN.objects.get(vid=2099, name="corporate")

If VLAN 2099 is not unique in your NetBox instance, add the appropriate scope/group/site filters as well.

Also note that Django lookups use double underscores. For example, vid__gt=2099 means “VID greater than 2099”, but in this case you probably want the exact VLAN ID, so vid=2099 is the better fit.

That said, I would avoid using <Model>.objects.create() in custom scripts, as it skips the opportunity to run model validation before saving. A safer pattern is:

corporate_prefix = Prefix(
    prefix=data["corporate_ipsubnet"],
    scope=site,
    vlan=corporate_vlan,
)
corporate_prefix.full_clean()
corporate_prefix.save()

Hope that helps!

[jesper-munk2]

Pheus This certainly looks very useful. I will look at it and test, and give You feedback.

[jesper-munk2]

Pheus I changed to use Your code, works fine:
# Generate Prefixes for site
# Prefix for VRF corporate
[vrf, vlan] = self.get_vrf_vlan(
vrf_name="corporate"
)

    corporate_prefix = Prefix(
        prefix=data["corporate_ipsubnet"],
        scope=site,
        vlan=vlan,
        vrf=vrf
    )
    corporate_prefix.full_clean()
    corporate_prefix.save()

Another question:
When I create the prefix with the above code, and also when I did with my "own" code, I create the desired prefix with the desired VLAN and VRF ok, but the code also results in the same prefix being created within the same site but with no VLAN and with VRF Global, see screenshot below. Do You know why this happens / can You send me link to documentation about this behaviour , and for at way to delete this "second" prefix with VRF Global.

When I attempt to tlelete the above corporate_prefix with the below code, I get the following error for the Prefix.objects.get statement:

An exception occurred: FieldError: Field 'scope' does not generate an automatic reverse relation and therefore cannot be used for reverse querying. If it is a GenericForeignKey, consider adding a GenericRelation.

corporate_prefix_no_vrf_vlan = Prefix.objects.get(
prefix=data["corporate_ipsubnet"],
scope=site,
vlan=None,
vrf=None,
)
self.log_debug(f"corporate_prefix_no_vrf_vlan: {corporate_prefix_no_vrf_vlan}")
corporate_prefix_no_vrf_vlan.delete()
self.log_debug(f"Deleted corporate_prefix_no_vrf_vlan: {corporate_prefix_no_vrf_vlan}")

Again: can You provide link to documentation about why the above happens, and how to delete the Prefix with no VLAN and VRF Global?

[jesper-munk2]

Pheus I have created new discussion #22121 about my above additional question, that I get two prefixes created, one within the VRF and VLAN, and one within VRF Global. This is the most fair, as it is a separate issue. So I will close this discussion with this.

[pheus]

The follow-up question is closely related to the original custom script and prefix creation topic, so it is better to keep everything in the same discussion. That way, anyone from the community who wants to help can easily follow the full context, including the previous code, suggestions, and how you got to the current situation.

I’ve reopened this discussion so we can continue here.