From f25dd7aab702b71467665f1b1ddb4ece81e52220 Mon Sep 17 00:00:00 2001
From: Jad Seifeddine <jseifeddine@macquarietelecom.com>
Date: Wed, 30 Jul 2025 13:56:32 +1000
Subject: [PATCH] Fix MAC address pagination duplicates by adding 'pk' to model
 ordering

Add 'pk' to MACAddress model ordering to ensure deterministic results
when multiple MAC addresses have the same value. This prevents the same
MAC address from appearing on multiple pages during pagination.

The issue occurred because Django's default ordering by 'mac_address'
alone is non-deterministic when multiple records share the same MAC
address value, causing inconsistent pagination results when the same
MAC address is assigned to multiple interfaces on a device.

Added regression test that verifies MAC addresses with identical values
are properly ordered by their primary key, ensuring consistent pagination
behavior across the application.

Fixes netbox-community#19917
---
 .../0209_alter_macaddress_options.py          | 19 ++++++++++
 netbox/dcim/models/devices.py                 |  2 +-
 netbox/dcim/tests/test_models.py              | 36 +++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)
 create mode 100644 netbox/dcim/migrations/0209_alter_macaddress_options.py

diff --git a/netbox/dcim/migrations/0209_alter_macaddress_options.py b/netbox/dcim/migrations/0209_alter_macaddress_options.py
new file mode 100644
index 000000000..2f3b6de06
--- /dev/null
+++ b/netbox/dcim/migrations/0209_alter_macaddress_options.py
@@ -0,0 +1,19 @@
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('dcim', '0208_devicerole_uniqueness'),
+    ]
+
+    operations = [
+        migrations.AlterModelOptions(
+            name='macaddress',
+            options={
+                'ordering': ('mac_address', 'pk'),
+                'verbose_name': 'MAC address',
+                'verbose_name_plural': 'MAC addresses'
+            },
+        ),
+    ]
diff --git a/netbox/dcim/models/devices.py b/netbox/dcim/models/devices.py
index abd29d4e3..e1ad9c15c 100644
--- a/netbox/dcim/models/devices.py
+++ b/netbox/dcim/models/devices.py
@@ -1276,7 +1276,7 @@ class MACAddress(PrimaryModel):
     )
 
     class Meta:
-        ordering = ('mac_address',)
+        ordering = ('mac_address', 'pk',)
         verbose_name = _('MAC address')
         verbose_name_plural = _('MAC addresses')
 
diff --git a/netbox/dcim/tests/test_models.py b/netbox/dcim/tests/test_models.py
index be9f067d4..103795766 100644
--- a/netbox/dcim/tests/test_models.py
+++ b/netbox/dcim/tests/test_models.py
@@ -37,6 +37,19 @@ class MACAddressTestCase(TestCase):
         cls.interface.primary_mac_address = cls.mac_a
         cls.interface.save()
 
+        shared_mac = '1234567890ab'
+        interfaces = []
+        for i in range(10):
+            interfaces.append(Interface(
+                device=device, name=f'Interface {i:03d}', type='1000base-t'
+            ))
+        Interface.objects.bulk_create(interfaces)
+
+        mac_addresses = []
+        for interface in interfaces:
+            mac_addresses.append(MACAddress(mac_address=shared_mac, assigned_object=interface))
+        MACAddress.objects.bulk_create(mac_addresses)
+
     @tag('regression')
     def test_clean_will_not_allow_removal_of_assigned_object_if_primary(self):
         self.mac_a.assigned_object = None
@@ -48,6 +61,29 @@ class MACAddressTestCase(TestCase):
         self.mac_b.assigned_object = None
         self.mac_b.clean()
 
+    @tag('regression')
+    def test_mac_address_ordering_with_duplicates(self):
+        """
+        Test that MAC addresses with the same value are ordered by their primary key (pk).
+        This ensures deterministic ordering for pagination when multiple records share the same MAC address.
+        """
+        mac_addresses = list(MACAddress.objects.all())
+
+        mac_address_groups = {}
+        for mac in mac_addresses:
+            if mac.mac_address not in mac_address_groups:
+                mac_address_groups[mac.mac_address] = []
+            mac_address_groups[mac.mac_address].append(mac)
+
+        for mac_value, macs in mac_address_groups.items():
+            if len(macs) > 1:
+                for i in range(1, len(macs)):
+                    self.assertLess(
+                        macs[i - 1].pk,
+                        macs[i].pk,
+                        f"MAC addresses with value {mac_value} are not ordered by primary key"
+                    )
+
 
 class LocationTestCase(TestCase):