Fixes: #15924 - Prevent API payload from allowing tagged_vlans while interface mode is set to tagged-all

netbox/dcim/api/serializers_/device_components.py

@@ -1,3 +1,4 @@
+from django.utils.translation import gettext as _
 from django.contrib.contenttypes.models import ContentType
 from drf_spectacular.utils import extend_schema_field
 from rest_framework import serializers
@@ -236,8 +237,8 @@ class Meta:
 
     def validate(self, data):
 
-        # Validate many-to-many VLAN assignments
         if not self.nested:
+            # Validate many-to-many VLAN assignments
             device = self.instance.device if self.instance else data.get('device')
             for vlan in data.get('tagged_vlans', []):
                 if vlan.site not in [device.site, None]:

netbox/dcim/models/device_components.py

@@ -904,6 +904,12 @@ def clean(self):
                 ).format(untagged_vlan=self.untagged_vlan)
             })
 
+        # Validate that tagged-all payload does not include tagged_vlans
+        if self.mode != InterfaceModeChoices.MODE_TAGGED and self.tagged_vlans:
+            raise ValidationError({
+                'tagged_vlans': "Interface mode does not support including tagged vlans"
+            })
+
     def save(self, *args, **kwargs):
 
         # Set absolute channel attributes from selected options