diff --git a/tests/unittests/conftest.py b/tests/unittests/conftest.py
index 20dc5cc594ed..f291aee03b98 100644
--- a/tests/unittests/conftest.py
+++ b/tests/unittests/conftest.py
@@ -101,6 +101,26 @@ def disable_sysfs_net(tmpdir_factory):
         yield mock_sysfs
 
 
+@pytest.fixture(scope="session", autouse=True)
+def disable_sysfs_net(request, tmpdir_factory):
+    """Avoid tests which read the undertying host's /syc/class/net.
+
+    To allow unobscured reads of /sys/class/net on the host we can
+    parametrize the fixture with:
+
+    @pytest.mark.parametrize("disable_sysfs_net", [False], indirect=True)
+    """
+    if hasattr(request, "param") and getattr(request, "param") is False:
+        # Test disabled this fixture, perform no mocks.
+        yield
+        return
+    mock_sysfs = f"{tmpdir_factory.mktemp('sysfs')}/"
+    with mock.patch(
+        "cloudinit.net.get_sys_class_path", return_value=mock_sysfs
+    ):
+        yield mock_sysfs
+
+
 @pytest.fixture(autouse=True)
 def disable_dns_lookup(request):
     if "allow_dns_lookup" in request.keywords: