diff --git a/module/sources/vmware/connection.py b/module/sources/vmware/connection.py
index cde3c53..8b14294 100644
--- a/module/sources/vmware/connection.py
+++ b/module/sources/vmware/connection.py
@@ -3246,9 +3246,11 @@ def add_host(self, obj):
             if vnic_ips.get(vnic_name) is None:
                 vnic_ips[vnic_name] = list()
 
-            int_v4 = "{}/{}".format(grab(vnic, "spec.ip.ipAddress"), grab(vnic, "spec.ip.subnetMask"))
+            vnic_ipv4 = grab(vnic, "spec.ip.ipAddress")
+            int_v4 = "{}/{}".format(vnic_ipv4, grab(vnic, "spec.ip.subnetMask"))
 
-            if self.settings.permitted_subnets.permitted(int_v4, interface_name=vnic_name) is True:
+            # a vmk without IPv4 (VxRail hosts' vmk0) reports an empty address: nothing to add
+            if vnic_ipv4 and self.settings.permitted_subnets.permitted(int_v4, interface_name=vnic_name) is True:
                 vnic_ips[vnic_name].append(int_v4)
 
                 if vnic_is_primary is True and host_primary_ip4 is None:
diff --git a/tests/test_vmware_host_vmk_without_ipv4.py b/tests/test_vmware_host_vmk_without_ipv4.py
new file mode 100644
index 0000000..c437496
--- /dev/null
+++ b/tests/test_vmware_host_vmk_without_ipv4.py
@@ -0,0 +1,103 @@
+# -*- 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>.
+
+"""
+A VMkernel interface without an IPv4 address reports an empty address and mask (Dell
+VxRail hosts' vmk0 carries IPv6 link-local addresses only). That is no address to
+add and no error: the interface is still synced, just without an IPv4 address,
+instead of logging "IP address '/' for vmk0 invalid!" on every run.
+
+vcsim has no UpdateVirtualNic, so the host's address is blanked in a copy of a
+captured inventory before vcsim loads it.
+"""
+import logging
+import re
+import subprocess
+import tarfile
+from types import SimpleNamespace
+
+import pytest
+
+from conftest import FIXTURE_DIR, _free_port, _wait_for_port
+from module.netbox.object_classes import NBDevice, NBInterface, NBIPAddress
+from module.sources import instantiate_sources
+
+DUMP = "vc001"
+_VMK0_IPV4 = re.compile(
+    r"(<vnic>\s*<device>vmk0</device>.*?<ip>\s*<dhcp>false</dhcp>\s*)"
+    r"<ipAddress>([^<]*)</ipAddress>\s*<subnetMask>[^<]*</subnetMask>",
+    re.S,
+)
+
+
+@pytest.fixture
+def vcsim_host_vmk0_without_ipv4(vcsim_binary, tmp_path):
+    with tarfile.open(FIXTURE_DIR / f"{DUMP}.tar.gz") as archive:
+        archive.extractall(tmp_path, filter="data")
+    load_dir = tmp_path / DUMP
+
+    for host_file in sorted(load_dir.glob("*-HostSystem-*.xml")):
+        text = host_file.read_text()
+        match = _VMK0_IPV4.search(text)
+        if match is not None:
+            host_file.write_text(text[:match.start()] + match.group(1) +
+                                 "<ipAddress></ipAddress><subnetMask></subnetMask>" + text[match.end():])
+            blanked_address = match.group(2)
+            break
+    else:
+        pytest.fail(f"no host in {DUMP} has a vmk0 with a static IPv4 address")
+
+    host, port = "127.0.0.1", _free_port()
+    process = subprocess.Popen([vcsim_binary, "-load", str(load_dir), "-l", f"{host}:{port}"],
+                               stdout=subprocess.DEVNULL, stderr=subprocess.PIPE)
+    try:
+        _wait_for_port(host, port, process)
+        yield SimpleNamespace(host=host, port=port, blanked_address=blanked_address)
+    finally:
+        process.terminate()
+        try:
+            process.wait(timeout=10)
+        except subprocess.TimeoutExpired:
+            process.kill()
+
+
+def test_vmk_without_ipv4_is_synced_without_error(vcsim_host_vmk0_without_ipv4, inventory, load_config, caplog):
+    sim = vcsim_host_vmk0_without_ipv4
+    load_config(f"""
+[netbox]
+api_token = not-used-by-these-tests
+host_fqdn = 127.0.0.1
+
+[source/{DUMP}]
+type = vmware
+host_fqdn = {sim.host}
+port = {sim.port}
+username = user
+password = pass
+validate_tls_certs = False
+permitted_subnets = 0.0.0.0/0, ::/0
+dns_name_lookup = False
+""")
+    sources = instantiate_sources()
+    assert sources and sources[0].init_successful
+    inventory.resolve_relations()
+
+    with caplog.at_level(logging.INFO):
+        sources[0].apply()
+
+    errors = [r.getMessage() for r in caplog.records if r.levelno >= logging.ERROR]
+    assert not [e for e in errors if "vmk0" in e], f"errors for vmk0: {errors}"
+
+    hosts = list(inventory.get_all_items(NBDevice))
+    vmk0 = [i for i in inventory.get_all_items(NBInterface) if i.data.get("name") == "vmk0"]
+    assert hosts and len(vmk0) == len(hosts), "every host must still have its vmk0 interface"
+
+    addresses = [ip.data.get("address", "").split("/")[0] for ip in inventory.get_all_items(NBIPAddress)]
+    assert sim.blanked_address not in addresses
+    assert "" not in addresses, "an empty IPv4 address was added"