diff --git a/module/sources/common/source_base.py b/module/sources/common/source_base.py
index df098e7..7537f51 100644
--- a/module/sources/common/source_base.py
+++ b/module/sources/common/source_base.py
@@ -165,7 +165,12 @@ def map_object_interfaces_to_current_interfaces(self, device_vm_object, interfac
 
         # grab current data
         for interface in self.inventory.get_all_interfaces(device_vm_object):
-            int_mac = grab(interface, "data.mac_address")
+            # from NetBox 4.2 on 'mac_address' is a read-only leftover of the last NetBox read which sources
+            # don't update. Use the current primary MAC address object instead.
+            if version.parse(self.inventory.netbox_api_version) >= version.parse("4.2.0"):
+                int_mac = grab(grab(interface, "data.primary_mac_address"), "data.mac_address")
+            else:
+                int_mac = grab(interface, "data.mac_address")
             int_name = grab(interface, "data.name")
 
             if interface_exclude_filter is not None and int_name is not None and \
diff --git a/tests/test_interface_matching_primary_mac.py b/tests/test_interface_matching_primary_mac.py
new file mode 100644
index 0000000..fa29309
--- /dev/null
+++ b/tests/test_interface_matching_primary_mac.py
@@ -0,0 +1,56 @@
+# -*- coding: utf-8 -*-
+#  Copyright (c) 2020 - 2026 netbox-sync team. All rights reserved.
+#
+#  netbox-sync.py
+#
+#  This work is licensed under the terms of the MIT license.
+#  For a copy, see file LICENSE.txt included in this
+#  repository or visit: <https://opensource.org/licenses/MIT>.
+
+"""Interface matching by MAC must use the current primary MAC address object (NetBox >= 4.2).
+
+The legacy interface 'mac_address' field is only what NetBox returned at read time. Once a
+previous source moved the primary MAC to another address, matching on the stale value merged
+a BMC port (i.e. Lenovo XCC) into the ESXi vmk0 interface on every run.
+"""
+
+from module.netbox.object_classes import NBInterface, NBMACAddress
+
+BMC_MAC = "38:68:DD:34:33:C5"
+VMK_MAC = "00:50:56:67:39:DA"
+
+
+def seed_vmk0(context, legacy_mac, primary_mac):
+    interface = context.inventory.add_object(
+        NBInterface, data={"name": "vmk0", "device": context.device, "type": "virtual", "mac_address": legacy_mac},
+        source=context.source)
+    mac_object = context.inventory.add_object(
+        NBMACAddress, data={"mac_address": primary_mac, "assigned_object_id": interface,
+                            "assigned_object_type": NBInterface}, source=context.source)
+    interface.update(data={"primary_mac_address": mac_object}, source=context.source)
+    return interface
+
+
+def bmc_port():
+    return {"XCC (1:NIC:abc)": {"name": "XCC (1:NIC:abc)", "mac_address": BMC_MAC, "type": "other",
+                                "mgmt_only": True}}
+
+
+def test_bmc_port_ignores_stale_legacy_mac(check_redfish_source):
+
+    context = check_redfish_source()
+    seed_vmk0(context, legacy_mac=BMC_MAC, primary_mac=VMK_MAC)
+
+    data = context.source.map_object_interfaces_to_current_interfaces(context.device, bmc_port(), True)
+
+    assert data["XCC (1:NIC:abc)"] is None
+
+
+def test_bmc_port_still_matches_by_primary_mac(check_redfish_source):
+
+    context = check_redfish_source()
+    vmk0 = seed_vmk0(context, legacy_mac=VMK_MAC, primary_mac=BMC_MAC)
+
+    data = context.source.map_object_interfaces_to_current_interfaces(context.device, bmc_port(), True)
+
+    assert data["XCC (1:NIC:abc)"] is vmk0