diff --git a/quantum/agent/linux/dhcp.py b/quantum/agent/linux/dhcp.py
index 54f620d783..fb1a68705f 100644
--- a/quantum/agent/linux/dhcp.py
+++ b/quantum/agent/linux/dhcp.py
@@ -367,8 +367,13 @@ class Dnsmasq(DhcpLocalProcess):
                     self._format_option(i, 'dns-server',
                                         ','.join(subnet.dns_nameservers)))
 
-            host_routes = ["%s,%s" % (hr.destination, hr.nexthop)
-                           for hr in subnet.host_routes]
+            gateway = subnet.gateway_ip
+            host_routes = []
+            for hr in subnet.host_routes:
+                if hr.destination == "0.0.0.0/0":
+                    gateway = hr.nexthop
+                else:
+                    host_routes.append("%s,%s" % (hr.destination, hr.nexthop))
 
             # Add host routes for isolated network segments
             enable_metadata = (
@@ -388,9 +393,8 @@ class Dnsmasq(DhcpLocalProcess):
                                         ','.join(host_routes)))
 
             if subnet.ip_version == 4:
-                if subnet.gateway_ip:
-                    options.append(self._format_option(i, 'router',
-                                                       subnet.gateway_ip))
+                if gateway:
+                    options.append(self._format_option(i, 'router', gateway))
                 else:
                     options.append(self._format_option(i, 'router'))
 
diff --git a/quantum/tests/unit/test_linux_dhcp.py b/quantum/tests/unit/test_linux_dhcp.py
index 0590922805..ed2f89f4e5 100644
--- a/quantum/tests/unit/test_linux_dhcp.py
+++ b/quantum/tests/unit/test_linux_dhcp.py
@@ -60,6 +60,11 @@ class FakeV4HostRoute:
     nexthop = '20.0.0.1'
 
 
+class FakeV4HostRouteGateway:
+    destination = '0.0.0.0/0'
+    nexthop = '10.0.0.1'
+
+
 class FakeV6HostRoute:
     destination = 'gdca:3ba5:a17a:4ba3::/64'
     nexthop = 'gdca:3ba5:a17a:4ba3::1'
@@ -75,6 +80,16 @@ class FakeV4Subnet:
     dns_nameservers = ['8.8.8.8']
 
 
+class FakeV4SubnetGatewayRoute:
+    id = 'dddddddd-dddd-dddd-dddd-dddddddddddd'
+    ip_version = 4
+    cidr = '192.168.0.0/24'
+    gateway_ip = '192.168.0.1'
+    enable_dhcp = True
+    host_routes = [FakeV4HostRouteGateway]
+    dns_nameservers = ['8.8.8.8']
+
+
 class FakeV6Subnet:
     id = 'ffffffff-ffff-ffff-ffff-ffffffffffff'
     ip_version = 6
@@ -123,6 +138,12 @@ class FakeDualNetwork:
     ports = [FakePort1(), FakePort2(), FakePort3()]
 
 
+class FakeDualNetworkGatewayRoute:
+    id = 'cccccccc-cccc-cccc-cccc-cccccccccccc'
+    subnets = [FakeV4SubnetGatewayRoute(), FakeV6Subnet()]
+    ports = [FakePort1(), FakePort2(), FakePort3()]
+
+
 class FakeDualNetworkSingleDHCP:
     id = 'cccccccc-cccc-cccc-cccc-cccccccccccc'
     subnets = [FakeV4Subnet(), FakeV4SubnetNoDHCP()]
@@ -495,6 +516,25 @@ tag:tag1,option:classless-static-route,%s,%s""".lstrip() % (fake_v6,
 
         self.safe.assert_called_once_with('/foo/opts', expected)
 
+    def test_output_opts_file_gateway_route(self):
+        fake_v6 = 'gdca:3ba5:a17a:4ba3::1'
+        fake_v6_cidr = 'gdca:3ba5:a17a:4ba3::/64'
+        expected = """
+tag:tag0,option:dns-server,8.8.8.8
+tag:tag0,option:router,10.0.0.1
+tag:tag1,option:dns-server,%s
+tag:tag1,option:classless-static-route,%s,%s""".lstrip() % (fake_v6,
+                                                            fake_v6_cidr,
+                                                            fake_v6)
+
+        with mock.patch.object(dhcp.Dnsmasq, 'get_conf_file_name') as conf_fn:
+            conf_fn.return_value = '/foo/opts'
+            dm = dhcp.Dnsmasq(self.conf, FakeDualNetworkGatewayRoute(),
+                              version=float(2.59))
+            dm._output_opts_file()
+
+        self.safe.assert_called_once_with('/foo/opts', expected)
+
     def test_output_opts_file_single_dhcp(self):
         expected = """
 tag:tag0,option:dns-server,8.8.8.8