diff --git a/neutron/agent/linux/dhcp.py b/neutron/agent/linux/dhcp.py
index 9ab3ff8ae4b..852a785a754 100644
--- a/neutron/agent/linux/dhcp.py
+++ b/neutron/agent/linux/dhcp.py
@@ -467,7 +467,7 @@ class Dnsmasq(DhcpLocalProcess):
         pm = self._get_process_manager(
             cmd_callback=self._build_cmdline_callback)
 
-        pm.enable(reload_cfg=reload_with_HUP)
+        pm.enable(reload_cfg=reload_with_HUP, ensure_active=True)
 
         self.process_monitor.register(uuid=self.network.id,
                                       service_name=DNSMASQ_SERVICE_NAME,
diff --git a/neutron/agent/linux/external_process.py b/neutron/agent/linux/external_process.py
index 6ba8a553019..f5bc1f89b0a 100644
--- a/neutron/agent/linux/external_process.py
+++ b/neutron/agent/linux/external_process.py
@@ -26,6 +26,7 @@ import six
 
 from neutron.agent.linux import ip_lib
 from neutron.agent.linux import utils
+from neutron.common import utils as common_utils
 from neutron.conf.agent import common as agent_cfg
 
 
@@ -78,7 +79,7 @@ class ProcessManager(MonitoredProcess):
         fileutils.ensure_tree(os.path.dirname(self.get_pid_file_name()),
                               mode=0o755)
 
-    def enable(self, cmd_callback=None, reload_cfg=False):
+    def enable(self, cmd_callback=None, reload_cfg=False, ensure_active=False):
         if not self.active:
             if not cmd_callback:
                 cmd_callback = self.default_cmd_callback
@@ -89,6 +90,8 @@ class ProcessManager(MonitoredProcess):
                                      run_as_root=self.run_as_root)
         elif reload_cfg:
             self.reload_cfg()
+        if ensure_active:
+            common_utils.wait_until_true(lambda: self.active)
 
     def reload_cfg(self):
         if self.custom_reload_callback:
diff --git a/neutron/tests/unit/agent/linux/test_dhcp.py b/neutron/tests/unit/agent/linux/test_dhcp.py
index 51dbd4a1951..a7c509f269b 100644
--- a/neutron/tests/unit/agent/linux/test_dhcp.py
+++ b/neutron/tests/unit/agent/linux/test_dhcp.py
@@ -1343,7 +1343,7 @@ class TestDnsmasq(TestBase):
 
             self.assertTrue(test_pm.register.called)
             self.external_process().enable.assert_called_once_with(
-                reload_cfg=False)
+                ensure_active=True, reload_cfg=False)
             call_kwargs = self.external_process.mock_calls[0][2]
             cmd_callback = call_kwargs['default_cmd_callback']
 
@@ -2108,7 +2108,7 @@ class TestDnsmasq(TestBase):
         dm.reload_allocations()
         self.assertTrue(test_pm.register.called)
         self.external_process().enable.assert_called_once_with(
-            reload_cfg=True)
+            ensure_active=True, reload_cfg=True)
 
         self.safe.assert_has_calls([
             mock.call(exp_host_name, exp_host_data),
diff --git a/neutron/tests/unit/agent/linux/test_external_process.py b/neutron/tests/unit/agent/linux/test_external_process.py
index 55d8918ddab..9bf719f1a44 100644
--- a/neutron/tests/unit/agent/linux/test_external_process.py
+++ b/neutron/tests/unit/agent/linux/test_external_process.py
@@ -21,6 +21,7 @@ from oslo_utils import fileutils
 import psutil
 
 from neutron.agent.linux import external_process as ep
+from neutron.common import utils as common_utils
 from neutron.tests import base
 
 
@@ -169,6 +170,24 @@ class TestProcessManager(base.BaseTestCase):
                 manager.enable(callback)
                 self.assertFalse(callback.called)
 
+    def test_enable_with_ensure_active(self):
+        def _create_cmd(*args):
+            return ['sleep', 0]
+
+        pm = ep.ProcessManager(self.conf, 'uuid', pid_file='pid_file',
+                               default_cmd_callback=_create_cmd)
+        with mock.patch.object(psutil, 'Process') as mock_psutil_process, \
+                mock.patch.object(ep.ProcessManager, 'pid',
+                                  new_callable=mock.PropertyMock) as mock_pid:
+            mock_pid.return_value = 'pid_value'
+            mock_process = mock.Mock()
+            mock_process.cmdline.side_effect = [[], ['the', 'cmd', 'uuid']]
+            mock_psutil_process.return_value = mock_process
+            try:
+                pm.enable(ensure_active=True)
+            except common_utils.WaitTimeout:
+                self.fail('ProcessManager.enable() raised WaitTimeout')
+
     def test_reload_cfg_without_custom_reload_callback(self):
         with mock.patch.object(ep.ProcessManager, 'disable') as disable:
             manager = ep.ProcessManager(self.conf, 'uuid', namespace='ns')