diff --git a/neutron/agent/linux/ip_lib.py b/neutron/agent/linux/ip_lib.py
index 0cb2a87405d..c882da23528 100644
--- a/neutron/agent/linux/ip_lib.py
+++ b/neutron/agent/linux/ip_lib.py
@@ -40,7 +40,6 @@ OPTS = [
 
 LOOPBACK_DEVNAME = 'lo'
 
-IP_NETNS_PATH = '/var/run/netns'
 SYS_NET_PATH = '/sys/class/net'
 DEFAULT_GW_PATTERN = re.compile(r"via (\S+)")
 METRIC_PATTERN = re.compile(r"metric (\S+)")
@@ -246,10 +245,7 @@ class IPWrapper(SubProcessBase):
 
     @classmethod
     def get_namespaces(cls):
-        if not cfg.CONF.AGENT.use_helper_for_ns_read:
-            return os.listdir(IP_NETNS_PATH)
-
-        output = cls._execute([], 'netns', ['list'], run_as_root=True)
+        output = cls._execute([], 'netns', ('list',))
         return [l.split()[0] for l in output.splitlines()]
 
 
@@ -879,11 +875,9 @@ class IpNetnsCommand(IpCommandBase):
                              log_fail_as_error=log_fail_as_error, **kwargs)
 
     def exists(self, name):
-        if not cfg.CONF.AGENT.use_helper_for_ns_read:
-            return name in os.listdir(IP_NETNS_PATH)
-
         output = self._parent._execute(
-            ['o'], 'netns', ['list'], run_as_root=True)
+            ['o'], 'netns', ['list'],
+            run_as_root=cfg.CONF.AGENT.use_helper_for_ns_read)
         for line in [l.split()[0] for l in output.splitlines()]:
             if name == line:
                 return True
diff --git a/neutron/tests/functional/agent/linux/test_ip_lib.py b/neutron/tests/functional/agent/linux/test_ip_lib.py
index 3389bcc1c2d..4be32098656 100644
--- a/neutron/tests/functional/agent/linux/test_ip_lib.py
+++ b/neutron/tests/functional/agent/linux/test_ip_lib.py
@@ -86,12 +86,6 @@ class IpLibTestFramework(functional_base.BaseSudoTestCase):
 
 
 class IpLibTestCase(IpLibTestFramework):
-    def test_namespace_exists(self):
-        namespace = self.useFixture(net_helpers.NamespaceFixture())
-        self.assertTrue(namespace.ip_wrapper.netns.exists(namespace.name))
-        namespace.destroy()
-        self.assertFalse(namespace.ip_wrapper.netns.exists(namespace.name))
-
     def test_device_exists(self):
         attr = self.generate_device_details()
 
diff --git a/neutron/tests/unit/agent/linux/test_ip_lib.py b/neutron/tests/unit/agent/linux/test_ip_lib.py
index ed5856ee194..3a9f63c525e 100644
--- a/neutron/tests/unit/agent/linux/test_ip_lib.py
+++ b/neutron/tests/unit/agent/linux/test_ip_lib.py
@@ -15,7 +15,6 @@
 
 import mock
 import netaddr
-from oslo_config import cfg
 import testtools
 
 from neutron.agent.common import utils  # noqa
@@ -284,37 +283,23 @@ class TestIpWrapper(base.BaseTestCase):
 
     def test_get_namespaces(self):
         self.execute.return_value = '\n'.join(NETNS_SAMPLE)
-        cfg.CONF.AGENT.use_helper_for_ns_read = True
         retval = ip_lib.IPWrapper.get_namespaces()
         self.assertEqual(retval,
                          ['12345678-1234-5678-abcd-1234567890ab',
                           'bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb',
                           'cccccccc-cccc-cccc-cccc-cccccccccccc'])
 
-        self.execute.assert_called_once_with([], 'netns', ['list'],
-                                             run_as_root=True)
+        self.execute.assert_called_once_with([], 'netns', ('list',))
 
     def test_get_namespaces_iproute2_4(self):
         self.execute.return_value = '\n'.join(NETNS_SAMPLE_IPROUTE2_4)
-        cfg.CONF.AGENT.use_helper_for_ns_read = True
         retval = ip_lib.IPWrapper.get_namespaces()
         self.assertEqual(retval,
                          ['12345678-1234-5678-abcd-1234567890ab',
                           'bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb',
                           'cccccccc-cccc-cccc-cccc-cccccccccccc'])
 
-        self.execute.assert_called_once_with([], 'netns', ['list'],
-                                             run_as_root=True)
-
-    @mock.patch('os.listdir', return_value=NETNS_SAMPLE)
-    def test_get_namespaces_listdir(self, mocked_listdir):
-        cfg.CONF.AGENT.use_helper_for_ns_read = False
-        retval = ip_lib.IPWrapper.get_namespaces()
-        self.assertEqual(retval,
-                         ['12345678-1234-5678-abcd-1234567890ab',
-                          'bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb',
-                          'cccccccc-cccc-cccc-cccc-cccccccccccc'])
-        mocked_listdir.assert_called_once_with(ip_lib.IP_NETNS_PATH)
+        self.execute.assert_called_once_with([], 'netns', ('list',))
 
     def test_add_tuntap(self):
         ip_lib.IPWrapper().add_tuntap('tap0')
@@ -1184,6 +1169,32 @@ class TestIpNetnsCommand(TestIPCmdBase):
             self.netns_cmd.delete('ns')
             self._assert_sudo([], ('delete', 'ns'), use_root_namespace=True)
 
+    def test_namespace_exists_use_helper(self):
+        self.config(group='AGENT', use_helper_for_ns_read=True)
+        retval = '\n'.join(NETNS_SAMPLE)
+        # need another instance to avoid mocking
+        netns_cmd = ip_lib.IpNetnsCommand(ip_lib.SubProcessBase())
+        with mock.patch('neutron.agent.common.utils.execute') as execute:
+            execute.return_value = retval
+            self.assertTrue(
+                netns_cmd.exists('bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb'))
+            execute.assert_called_once_with(['ip', '-o', 'netns', 'list'],
+                                            run_as_root=True,
+                                            log_fail_as_error=True)
+
+    def test_namespace_doest_not_exist_no_helper(self):
+        self.config(group='AGENT', use_helper_for_ns_read=False)
+        retval = '\n'.join(NETNS_SAMPLE)
+        # need another instance to avoid mocking
+        netns_cmd = ip_lib.IpNetnsCommand(ip_lib.SubProcessBase())
+        with mock.patch('neutron.agent.common.utils.execute') as execute:
+            execute.return_value = retval
+            self.assertFalse(
+                netns_cmd.exists('bbbbbbbb-1111-2222-3333-bbbbbbbbbbbb'))
+            execute.assert_called_once_with(['ip', '-o', 'netns', 'list'],
+                                            run_as_root=False,
+                                            log_fail_as_error=True)
+
     def test_execute(self):
         self.parent.namespace = 'ns'
         with mock.patch('neutron.agent.common.utils.execute') as execute: