Fixes #21960: Trace multi-position front ports whose rear ports converge on one endpoint (#23649)

netbox/dcim/models/cables.py

@@ -993,6 +993,9 @@ class CablePath(models.Model):
         is_complete = False
         is_active = True
         is_split = False
+        # Whether the trace fanned out across a multi-position front port without positional context
+        fanout = False
+        diverged = False
 
         logger.debug(f'Tracing cable path from {terminations}...')
 
@@ -1012,7 +1015,11 @@ class CablePath(models.Model):
                 not isinstance(terminations[0].parent_object, Circuit) and
                 not all(t.parent_object == terminations[0].parent_object for t in terminations[1:])
             ):
-                raise UnsupportedCablePath(_("All mid-span terminations must have the same parent object"))
+                if not fanout:
+                    raise UnsupportedCablePath(_("All mid-span terminations must have the same parent object"))
+                # Fanned-out branches crossing different devices are not followed, even if they reconverge later
+                diverged = True
+                break
 
             # Check for a split path (e.g. rear port fanning out to multiple front ports with
             # different cables attached)
@@ -1177,15 +1184,13 @@ class CablePath(models.Model):
                     for rt in remote_terminations:
                         q_filter |= Q(front_port=rt, front_port_position__in=positions)
                     port_mappings = PortMapping.objects.filter(q_filter)
-                elif remote_terminations[0].positions > 1:
-                    is_split = True
-                    logger.debug(
-                        'Encountered front port mapped to multiple rear ports but position stack is empty; aborting '
-                        'trace.'
-                    )
-                    break
                 else:
-                    port_mappings = PortMapping.objects.filter(front_port__in=remote_terminations)
+                    # Without positional context, follow all mappings; branches must converge on one endpoint
+                    if any(t.positions > 1 for t in remote_terminations):
+                        fanout = True
+                    port_mappings = PortMapping.objects.filter(
+                        front_port__in=remote_terminations
+                    ).order_by('front_port', 'front_port_position')
                 if not port_mappings:
                     break
 
@@ -1257,7 +1262,10 @@ class CablePath(models.Model):
 
             else:
                 # Check for non-symmetric path
-                if all(isinstance(t, type(remote_terminations[0])) for t in remote_terminations[1:]):
+                # Fanned-out branches arriving over separate links reach different endpoints
+                if fanout and len(links) > 1:
+                    diverged = True
+                elif all(isinstance(t, type(remote_terminations[0])) for t in remote_terminations[1:]):
                     is_complete = True
                 elif len(remote_terminations) == 0:
                     is_complete = False
@@ -1268,6 +1276,12 @@ class CablePath(models.Model):
                     logger.warning('Encountered an unsupported topology; aborting trace.')
                 break
 
+        if diverged:
+            # Keep the full trace so changes to any branch retrace this path
+            logger.debug('Front port branches diverged; treating path as split.')
+            is_complete = False
+            is_split = True
+
         return cls(
             path=path,
             is_complete=is_complete,
@@ -1372,7 +1386,8 @@ class CablePath(models.Model):
 
     def get_split_nodes(self):
         """
-        Return all available next segments in a split cable path.
+        Return all available next segments in a split cable path, or the diverging endpoints if the path fanned
+        out across a multi-position front port.
         """
         from circuits.models import CircuitTermination
         nodes = self.path_objects[-1]
@@ -1395,6 +1410,9 @@ class CablePath(models.Model):
             return [
                 ct.get_peer_termination() for ct in nodes
             ]
+        # Front port branches diverging to different endpoints
+        if isinstance(nodes[0], PathEndpoint):
+            return nodes
         return []
 
     def get_asymmetric_nodes(self):

netbox/dcim/tests/test_cablepaths.py

@@ -2746,6 +2746,528 @@ class LegacyCablePathTestCase(BaseCablePathTestCase):
         cablepath.delete()
         self.assertIsNone(CablePath.objects.filter(pk=cablepath.pk).first())
 
+    def test_226_multiposition_frontport_to_converging_rear_ports(self):
+        """
+        [IF1] --C1-- [FP1:1] [RP1] --C2-- [RP3] [FP2] --C4-- [IF2]
+                     [FP1:2] [RP2] --C3-- [RP4] [FP3]
+        """
+        interface1 = Interface.objects.create(device=self.device, name='Interface 1')
+        interface2 = Interface.objects.create(device=self.device, name='Interface 2')
+        rearport1 = RearPort.objects.create(device=self.device, name='Rear Port 1')
+        rearport2 = RearPort.objects.create(device=self.device, name='Rear Port 2')
+        rearport3 = RearPort.objects.create(device=self.device, name='Rear Port 3')
+        rearport4 = RearPort.objects.create(device=self.device, name='Rear Port 4')
+        frontport1 = FrontPort.objects.create(device=self.device, name='Front Port 1', positions=2)
+        frontport2 = FrontPort.objects.create(device=self.device, name='Front Port 2')
+        frontport3 = FrontPort.objects.create(device=self.device, name='Front Port 3')
+        PortMapping.objects.bulk_create([
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=1,
+                rear_port=rearport1, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=2,
+                rear_port=rearport2, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport2, front_port_position=1,
+                rear_port=rearport3, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport3, front_port_position=1,
+                rear_port=rearport4, rear_port_position=1,
+            ),
+        ])
+
+        cable1 = Cable(a_terminations=[interface1], b_terminations=[frontport1])
+        cable1.save()
+        cable2 = Cable(a_terminations=[rearport1], b_terminations=[rearport3])
+        cable2.save()
+        cable3 = Cable(a_terminations=[rearport2], b_terminations=[rearport4])
+        cable3.save()
+        cable4 = Cable(a_terminations=[frontport2, frontport3], b_terminations=[interface2])
+        cable4.save()
+
+        path1 = self.assertPathExists(
+            (
+                interface1, cable1, frontport1, (rearport1, rearport2), (cable2, cable3),
+                (rearport3, rearport4), (frontport2, frontport3), cable4, interface2
+            ),
+            is_complete=True,
+            is_active=True,
+            is_split=False
+        )
+        path2 = self.assertPathExists(
+            (
+                interface2, cable4, (frontport2, frontport3), (rearport3, rearport4), (cable2, cable3),
+                (rearport1, rearport2), frontport1, cable1, interface1
+            ),
+            is_complete=True,
+            is_active=True,
+            is_split=False
+        )
+        self.assertEqual(CablePath.objects.count(), 2)
+        interface1.refresh_from_db()
+        interface2.refresh_from_db()
+        self.assertPathIsSet(interface1, path1)
+        self.assertPathIsSet(interface2, path2)
+
+    def test_227_multiposition_frontport_to_diverging_rear_ports(self):
+        """
+        [IF1] --C1-- [FP1:1] [RP1] --C2-- [IF2]
+                     [FP1:2] [RP2] --C3-- [IF3]
+        """
+        interface1 = Interface.objects.create(device=self.device, name='Interface 1')
+        interface2 = Interface.objects.create(device=self.device, name='Interface 2')
+        interface3 = Interface.objects.create(device=self.device, name='Interface 3')
+        rearport1 = RearPort.objects.create(device=self.device, name='Rear Port 1')
+        rearport2 = RearPort.objects.create(device=self.device, name='Rear Port 2')
+        frontport1 = FrontPort.objects.create(device=self.device, name='Front Port 1', positions=2)
+        PortMapping.objects.bulk_create([
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=1,
+                rear_port=rearport1, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=2,
+                rear_port=rearport2, rear_port_position=1,
+            ),
+        ])
+
+        cable1 = Cable(a_terminations=[interface1], b_terminations=[frontport1])
+        cable1.save()
+        cable2 = Cable(a_terminations=[rearport1], b_terminations=[interface2])
+        cable2.save()
+        cable3 = Cable(a_terminations=[rearport2], b_terminations=[interface3])
+        cable3.save()
+
+        # Branches reaching different endpoints are still treated as a split
+        path1 = self.assertPathExists(
+            (
+                interface1, cable1, frontport1, (rearport1, rearport2), (cable2, cable3),
+                (interface2, interface3)
+            ),
+            is_complete=False,
+            is_split=True
+        )
+        self.assertEqual(path1.get_split_nodes(), [interface2, interface3])
+        self.assertPathExists(
+            (interface2, cable2, rearport1, frontport1, cable1, interface1),
+            is_complete=True,
+            is_active=True
+        )
+        self.assertPathExists(
+            (interface3, cable3, rearport2, frontport1, cable1, interface1),
+            is_complete=True,
+            is_active=True
+        )
+        self.assertEqual(CablePath.objects.count(), 3)
+
+    def test_228_multiposition_frontport_to_crossed_rear_ports_on_remote_device(self):
+        """
+        Device A                                    Device B
+        [IF1] --C1-- [FP1:1] [RP1] --C2-- [RP4] [FP3] --C4-- [IF2]
+                     [FP1:2] [RP2] --C3-- [RP3] [FP2] --C4--
+        """
+        device_b = Device.objects.create(
+            site=self.site, device_type=self.device.device_type, role=self.device.role, name='Device B'
+        )
+        interface1 = Interface.objects.create(device=self.device, name='Interface 1')
+        interface2 = Interface.objects.create(device=device_b, name='Interface 2')
+        rearport1 = RearPort.objects.create(device=self.device, name='Rear Port 1')
+        rearport2 = RearPort.objects.create(device=self.device, name='Rear Port 2')
+        rearport3 = RearPort.objects.create(device=device_b, name='Rear Port 3')
+        rearport4 = RearPort.objects.create(device=device_b, name='Rear Port 4')
+        frontport1 = FrontPort.objects.create(device=self.device, name='Front Port 1', positions=2)
+        frontport2 = FrontPort.objects.create(device=device_b, name='Front Port 2')
+        frontport3 = FrontPort.objects.create(device=device_b, name='Front Port 3')
+        PortMapping.objects.bulk_create([
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=1,
+                rear_port=rearport1, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=2,
+                rear_port=rearport2, rear_port_position=1,
+            ),
+            PortMapping(
+                device=device_b, front_port=frontport2, front_port_position=1,
+                rear_port=rearport3, rear_port_position=1,
+            ),
+            PortMapping(
+                device=device_b, front_port=frontport3, front_port_position=1,
+                rear_port=rearport4, rear_port_position=1,
+            ),
+        ])
+
+        # TX/RX crossed between the two devices
+        cable1 = Cable(a_terminations=[interface1], b_terminations=[frontport1])
+        cable1.save()
+        cable2 = Cable(a_terminations=[rearport1], b_terminations=[rearport4])
+        cable2.save()
+        cable3 = Cable(a_terminations=[rearport2], b_terminations=[rearport3])
+        cable3.save()
+        cable4 = Cable(a_terminations=[frontport2, frontport3], b_terminations=[interface2])
+        cable4.save()
+
+        path1 = self.assertPathExists(
+            (
+                interface1, cable1, frontport1, (rearport1, rearport2), (cable2, cable3),
+                (rearport4, rearport3), (frontport2, frontport3), cable4, interface2
+            ),
+            is_complete=True,
+            is_active=True,
+            is_split=False
+        )
+        path2 = self.assertPathExists(
+            (
+                interface2, cable4, (frontport2, frontport3), (rearport3, rearport4), (cable3, cable2),
+                (rearport1, rearport2), frontport1, cable1, interface1
+            ),
+            is_complete=True,
+            is_active=True,
+            is_split=False
+        )
+        self.assertEqual(CablePath.objects.count(), 2)
+        interface1.refresh_from_db()
+        interface2.refresh_from_db()
+        self.assertPathIsSet(interface1, path1)
+        self.assertPathIsSet(interface2, path2)
+        self.assertEqual(interface1.connected_endpoints, [interface2])
+        self.assertEqual(interface2.connected_endpoints, [interface1])
+
+    def test_229_multiposition_frontport_to_rear_ports_on_different_devices(self):
+        """
+        [IF1] --C1-- [FP1:1] [RP1] --C2-- [RP3] [FP2]  (Device A)
+                     [FP1:2] [RP2] --C3-- [RP4] [FP3]  (Device B)
+        """
+        device_a = Device.objects.create(
+            site=self.site, device_type=self.device.device_type, role=self.device.role, name='Device A'
+        )
+        device_b = Device.objects.create(
+            site=self.site, device_type=self.device.device_type, role=self.device.role, name='Device B'
+        )
+        interface1 = Interface.objects.create(device=self.device, name='Interface 1')
+        rearport1 = RearPort.objects.create(device=self.device, name='Rear Port 1')
+        rearport2 = RearPort.objects.create(device=self.device, name='Rear Port 2')
+        rearport3 = RearPort.objects.create(device=device_a, name='Rear Port 3')
+        rearport4 = RearPort.objects.create(device=device_b, name='Rear Port 4')
+        frontport1 = FrontPort.objects.create(device=self.device, name='Front Port 1', positions=2)
+        frontport2 = FrontPort.objects.create(device=device_a, name='Front Port 2')
+        frontport3 = FrontPort.objects.create(device=device_b, name='Front Port 3')
+        PortMapping.objects.bulk_create([
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=1,
+                rear_port=rearport1, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=2,
+                rear_port=rearport2, rear_port_position=1,
+            ),
+            PortMapping(
+                device=device_a, front_port=frontport2, front_port_position=1,
+                rear_port=rearport3, rear_port_position=1,
+            ),
+            PortMapping(
+                device=device_b, front_port=frontport3, front_port_position=1,
+                rear_port=rearport4, rear_port_position=1,
+            ),
+        ])
+
+        cable1 = Cable(a_terminations=[interface1], b_terminations=[frontport1])
+        cable1.save()
+        cable2 = Cable(a_terminations=[rearport1], b_terminations=[rearport3], status=LinkStatusChoices.STATUS_PLANNED)
+        cable2.save()
+        cable3 = Cable(a_terminations=[rearport2], b_terminations=[rearport4])
+        cable3.save()
+
+        # Branches crossing different devices are not followed past the remote rear ports
+        path1 = self.assertPathExists(
+            (interface1, cable1, frontport1, (rearport1, rearport2), (cable2, cable3), (rearport3, rearport4)),
+            is_complete=False,
+            is_active=False,
+            is_split=True
+        )
+        self.assertEqual(CablePath.objects.count(), 1)
+        interface1.refresh_from_db()
+        self.assertPathIsSet(interface1, path1)
+
+    def test_230_multiposition_frontport_with_uncabled_rear_port(self):
+        """
+        [IF1] --C1-- [FP1:1] [RP1] --C2-- [RP3] [FP2] --C3-- [IF2]
+                     [FP1:2] [RP2]
+        """
+        interface1 = Interface.objects.create(device=self.device, name='Interface 1')
+        interface2 = Interface.objects.create(device=self.device, name='Interface 2')
+        rearport1 = RearPort.objects.create(device=self.device, name='Rear Port 1')
+        rearport2 = RearPort.objects.create(device=self.device, name='Rear Port 2')
+        rearport3 = RearPort.objects.create(device=self.device, name='Rear Port 3')
+        frontport1 = FrontPort.objects.create(device=self.device, name='Front Port 1', positions=2)
+        frontport2 = FrontPort.objects.create(device=self.device, name='Front Port 2')
+        PortMapping.objects.bulk_create([
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=1,
+                rear_port=rearport1, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=2,
+                rear_port=rearport2, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport2, front_port_position=1,
+                rear_port=rearport3, rear_port_position=1,
+            ),
+        ])
+
+        cable1 = Cable(a_terminations=[interface1], b_terminations=[frontport1])
+        cable1.save()
+        cable2 = Cable(a_terminations=[rearport1], b_terminations=[rearport3])
+        cable2.save()
+        cable3 = Cable(a_terminations=[frontport2], b_terminations=[interface2])
+        cable3.save()
+
+        # The uncabled branch is flagged as split (asymmetric), as for multi-termination cables
+        path1 = self.assertPathExists(
+            (
+                interface1, cable1, frontport1, (rearport1, rearport2), cable2, rearport3, frontport2, cable3,
+                interface2
+            ),
+            is_complete=True,
+            is_active=True,
+            is_split=True
+        )
+        path2 = self.assertPathExists(
+            (interface2, cable3, frontport2, rearport3, cable2, rearport1, frontport1, cable1, interface1),
+            is_complete=True,
+            is_active=True,
+            is_split=False
+        )
+        self.assertEqual(CablePath.objects.count(), 2)
+        interface1.refresh_from_db()
+        interface2.refresh_from_db()
+        self.assertPathIsSet(interface1, path1)
+        self.assertPathIsSet(interface2, path2)
+        self.assertEqual(interface1.connected_endpoints, [interface2])
+
+    def test_231_multiposition_frontport_rewire_diverged_to_converged(self):
+        """
+        [IF1] --C1-- [FP1:1] [RP1] --C2-- [RP3] [FP2] --C4-- [IF2]
+                     [FP1:2] [RP2] --C3-- [RP4] [FP3] --C5-- [IF3]
+        Rewired so that FP2 and FP3 both connect to IF2, then back again.
+        """
+        interface1 = Interface.objects.create(device=self.device, name='Interface 1')
+        interface2 = Interface.objects.create(device=self.device, name='Interface 2')
+        interface3 = Interface.objects.create(device=self.device, name='Interface 3')
+        rearport1 = RearPort.objects.create(device=self.device, name='Rear Port 1')
+        rearport2 = RearPort.objects.create(device=self.device, name='Rear Port 2')
+        rearport3 = RearPort.objects.create(device=self.device, name='Rear Port 3')
+        rearport4 = RearPort.objects.create(device=self.device, name='Rear Port 4')
+        frontport1 = FrontPort.objects.create(device=self.device, name='Front Port 1', positions=2)
+        frontport2 = FrontPort.objects.create(device=self.device, name='Front Port 2')
+        frontport3 = FrontPort.objects.create(device=self.device, name='Front Port 3')
+        PortMapping.objects.bulk_create([
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=1,
+                rear_port=rearport1, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=2,
+                rear_port=rearport2, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport2, front_port_position=1,
+                rear_port=rearport3, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport3, front_port_position=1,
+                rear_port=rearport4, rear_port_position=1,
+            ),
+        ])
+
+        def assert_path_is_current(interface):
+            interface.refresh_from_db()
+            stored = interface.path
+            traced = CablePath.from_origin([interface])
+            self.assertEqual(
+                (stored.path, stored.is_complete, stored.is_active, stored.is_split),
+                (traced.path, traced.is_complete, traced.is_active, traced.is_split),
+            )
+            return stored
+
+        cable1 = Cable(a_terminations=[interface1], b_terminations=[frontport1])
+        cable1.save()
+        cable2 = Cable(a_terminations=[rearport1], b_terminations=[rearport3])
+        cable2.save()
+        cable3 = Cable(a_terminations=[rearport2], b_terminations=[rearport4])
+        cable3.save()
+        cable4 = Cable(a_terminations=[frontport2], b_terminations=[interface2])
+        cable4.save()
+        cable5 = Cable(a_terminations=[frontport3], b_terminations=[interface3])
+        cable5.save()
+        path1 = assert_path_is_current(interface1)
+        self.assertTrue(path1.is_split)
+        self.assertFalse(path1.is_complete)
+
+        # Removing one branch's endpoint leaves the other branch complete (and asymmetric)
+        cable5.delete()
+        path1 = assert_path_is_current(interface1)
+        self.assertTrue(path1.is_complete)
+
+        # Converge both branches on a single endpoint
+        cable4.delete()
+        cable6 = Cable(a_terminations=[frontport2, frontport3], b_terminations=[interface2])
+        cable6.save()
+        path1 = assert_path_is_current(interface1)
+        self.assertTrue(path1.is_complete)
+        self.assertFalse(path1.is_split)
+        self.assertEqual(Interface.objects.get(pk=interface1.pk).connected_endpoints, [interface2])
+        self.assertEqual(Interface.objects.get(pk=interface2.pk).connected_endpoints, [interface1])
+
+        # Diverge the branches again
+        cable6.delete()
+        cable7 = Cable(a_terminations=[frontport2], b_terminations=[interface2])
+        cable7.save()
+        cable8 = Cable(a_terminations=[frontport3], b_terminations=[interface3])
+        cable8.save()
+        path1 = assert_path_is_current(interface1)
+        self.assertTrue(path1.is_split)
+        self.assertFalse(path1.is_complete)
+        self.assertEqual(Interface.objects.get(pk=interface1.pk).connected_endpoints, [])
+
+    def test_232_multiposition_frontport_reconverged_to_multiple_interfaces(self):
+        """
+        [IF1] --C1-- [FP1:1] [RP1:1] --C2-- [RP2:1] [FP2:1] --C3-- [IF2]
+                     [FP1:2] [RP1:2]        [RP2:2] [FP2:2]        [IF3]
+        """
+        interface1 = Interface.objects.create(device=self.device, name='Interface 1')
+        interface2 = Interface.objects.create(device=self.device, name='Interface 2')
+        interface3 = Interface.objects.create(device=self.device, name='Interface 3')
+        rearport1 = RearPort.objects.create(device=self.device, name='Rear Port 1', positions=2)
+        rearport2 = RearPort.objects.create(device=self.device, name='Rear Port 2', positions=2)
+        frontport1 = FrontPort.objects.create(device=self.device, name='Front Port 1', positions=2)
+        frontport2 = FrontPort.objects.create(device=self.device, name='Front Port 2', positions=2)
+        PortMapping.objects.bulk_create([
+            PortMapping(
+                device=self.device, front_port=frontport, front_port_position=position,
+                rear_port=rearport, rear_port_position=position,
+            )
+            for frontport, rearport in ((frontport1, rearport1), (frontport2, rearport2))
+            for position in (1, 2)
+        ])
+
+        cable1 = Cable(a_terminations=[interface1], b_terminations=[frontport1])
+        cable1.save()
+        cable2 = Cable(a_terminations=[rearport1], b_terminations=[rearport2])
+        cable2.save()
+        cable3 = Cable(a_terminations=[frontport2], b_terminations=[interface2, interface3])
+        cable3.save()
+
+        # Branches reconverge on RP1, so the final multi-termination cable is not a split
+        self.assertPathExists(
+            (
+                interface1, cable1, frontport1, rearport1, cable2, rearport2, frontport2, cable3,
+                (interface2, interface3)
+            ),
+            is_complete=True,
+            is_active=True,
+            is_split=False
+        )
+
+    def test_233_mixed_position_frontports_to_diverging_rear_ports(self):
+        """
+        [IF1] --C1-- [FP1]   [RP1] --C2-- [IF3]
+        [IF2]        [FP2:1] [RP2] --C3-- [IF4]
+                     [FP2:2] [RP3] --C4-- [IF5]
+        """
+        interface1 = Interface.objects.create(device=self.device, name='Interface 1')
+        interface2 = Interface.objects.create(device=self.device, name='Interface 2')
+        interface3 = Interface.objects.create(device=self.device, name='Interface 3')
+        interface4 = Interface.objects.create(device=self.device, name='Interface 4')
+        interface5 = Interface.objects.create(device=self.device, name='Interface 5')
+        rearport1 = RearPort.objects.create(device=self.device, name='Rear Port 1')
+        rearport2 = RearPort.objects.create(device=self.device, name='Rear Port 2')
+        rearport3 = RearPort.objects.create(device=self.device, name='Rear Port 3')
+        frontport1 = FrontPort.objects.create(device=self.device, name='Front Port 1')
+        frontport2 = FrontPort.objects.create(device=self.device, name='Front Port 2', positions=2)
+        PortMapping.objects.bulk_create([
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=1,
+                rear_port=rearport1, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport2, front_port_position=1,
+                rear_port=rearport2, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport2, front_port_position=2,
+                rear_port=rearport3, rear_port_position=1,
+            ),
+        ])
+
+        # The single-position front port is the first termination on the cable
+        cable1 = Cable(a_terminations=[interface1, interface2], b_terminations=[frontport1, frontport2])
+        cable1.save()
+        for rearport, interface in ((rearport1, interface3), (rearport2, interface4), (rearport3, interface5)):
+            Cable(a_terminations=[rearport], b_terminations=[interface]).save()
+
+        interface1.refresh_from_db()
+        self.assertFalse(interface1.path.is_complete)
+        self.assertTrue(interface1.path.is_split)
+
+    def test_234_multiposition_frontport_reconverged_then_diverging(self):
+        """
+        [IF1] --C1-- [FP1:1] [RP1:1] --C2-- [RP2:1] [FP2] --C3-- [IF2]
+                     [FP1:2] [RP1:2]        [RP2:2] [FP3] --C4-- [IF3]
+        """
+        interface1 = Interface.objects.create(device=self.device, name='Interface 1')
+        interface2 = Interface.objects.create(device=self.device, name='Interface 2')
+        interface3 = Interface.objects.create(device=self.device, name='Interface 3')
+        rearport1 = RearPort.objects.create(device=self.device, name='Rear Port 1', positions=2)
+        rearport2 = RearPort.objects.create(device=self.device, name='Rear Port 2', positions=2)
+        frontport1 = FrontPort.objects.create(device=self.device, name='Front Port 1', positions=2)
+        frontport2 = FrontPort.objects.create(device=self.device, name='Front Port 2')
+        frontport3 = FrontPort.objects.create(device=self.device, name='Front Port 3')
+        PortMapping.objects.bulk_create([
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=1,
+                rear_port=rearport1, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport1, front_port_position=2,
+                rear_port=rearport1, rear_port_position=2,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport2, front_port_position=1,
+                rear_port=rearport2, rear_port_position=1,
+            ),
+            PortMapping(
+                device=self.device, front_port=frontport3, front_port_position=1,
+                rear_port=rearport2, rear_port_position=2,
+            ),
+        ])
+
+        cable1 = Cable(a_terminations=[interface1], b_terminations=[frontport1])
+        cable1.save()
+        cable2 = Cable(a_terminations=[rearport1], b_terminations=[rearport2])
+        cable2.save()
+        cable3 = Cable(a_terminations=[frontport2], b_terminations=[interface2])
+        cable3.save()
+        cable4 = Cable(a_terminations=[frontport3], b_terminations=[interface3])
+        cable4.save()
+
+        # Reconverging on RP1 does not hide the branches diverging again at RP2
+        path1 = self.assertPathExists(
+            (
+                interface1, cable1, frontport1, rearport1, cable2, rearport2, (frontport2, frontport3),
+                (cable3, cable4), (interface2, interface3)
+            ),
+            is_complete=False,
+            is_split=True
+        )
+        self.assertEqual(path1.get_split_nodes(), [interface2, interface3])
+        interface1.refresh_from_db()
+        self.assertEqual(interface1.connected_endpoints, [])
+
     def test_301_create_path_via_existing_cable(self):
         """
         [IF1] --C1-- [FP1] [RP1] --C2-- [RP2] [FP2] --C3-- [IF2]