diff --git a/controller.yaml b/controller.yaml
index 5596591f28..bb70b28f29 100644
--- a/controller.yaml
+++ b/controller.yaml
@@ -257,6 +257,10 @@ parameters:
     type: string
     hidden: true
     default: ''  # Has to be here because of the ignored empty value bug
+  NeutronExternalNetworkBridge:
+    description: Name of bridge used for external network traffic.
+    type: string
+    default: 'br-ex'
   NeutronBridgeMappings:
     description: >
       The OVS logical->physical bridge mappings to use. See the Neutron
diff --git a/environments/net-bond-with-vlans.yaml b/environments/net-bond-with-vlans.yaml
index 38c31cac0a..73f71324cb 100644
--- a/environments/net-bond-with-vlans.yaml
+++ b/environments/net-bond-with-vlans.yaml
@@ -11,3 +11,9 @@ resource_registry:
   OS::TripleO::Controller::Net::SoftwareConfig: ../network/config/bond-with-vlans/controller.yaml
   OS::TripleO::ObjectStorage::Net::SoftwareConfig: ../network/config/bond-with-vlans/swift-storage.yaml
   OS::TripleO::CephStorage::Net::SoftwareConfig: ../network/config/bond-with-vlans/ceph-storage.yaml
+
+parameters:
+  # This sets 'external_network_bridge' in l3_agent.ini to an empty string
+  # so that external networks act like provider bridge networks (they
+  # will plug into br-int instead of br-ex)
+  NeutronExternalNetworkBridge: "''"
diff --git a/environments/net-single-nic-with-vlans.yaml b/environments/net-single-nic-with-vlans.yaml
index b087b3e4cc..8561acd39a 100644
--- a/environments/net-single-nic-with-vlans.yaml
+++ b/environments/net-single-nic-with-vlans.yaml
@@ -11,3 +11,9 @@ resource_registry:
   OS::TripleO::Controller::Net::SoftwareConfig: ../network/config/single-nic-vlans/controller.yaml
   OS::TripleO::ObjectStorage::Net::SoftwareConfig: ../network/config/single-nic-vlans/swift-storage.yaml
   OS::TripleO::CephStorage::Net::SoftwareConfig: ../network/config/single-nic-vlans/ceph-storage.yaml
+
+parameters:
+  # This sets 'external_network_bridge' in l3_agent.ini to an empty string
+  # so that external networks act like provider bridge networks (they
+  # will plug into br-int instead of br-ex)
+  NeutronExternalNetworkBridge: "''"
diff --git a/overcloud-without-mergepy.yaml b/overcloud-without-mergepy.yaml
index 14e2ac243b..aa8e939131 100644
--- a/overcloud-without-mergepy.yaml
+++ b/overcloud-without-mergepy.yaml
@@ -76,6 +76,10 @@ parameters:
     type: string
     constraints:
       - custom_constraint: nova.keypair
+  NeutronExternalNetworkBridge:
+    description: Name of bridge used for external network traffic.
+    type: string
+    default: 'br-ex'
   NeutronBridgeMappings:
     description: >
       The OVS logical->physical bridge mappings to use. See the Neutron
@@ -691,6 +695,7 @@ resources:
           NeutronPublicInterfaceIP: {get_param: NeutronPublicInterfaceIP}
           NeutronFlatNetworks: {get_param: NeutronFlatNetworks}
           NeutronBridgeMappings: {get_param: NeutronBridgeMappings}
+          NeutronExternalNetworkBridge: {get_param: NeutronExternalNetworkBridge}
           NeutronEnableTunnelling: {get_param: NeutronEnableTunnelling}
           NeutronNetworkVLANRanges: {get_param: NeutronNetworkVLANRanges}
           NeutronPublicInterface: {get_param: NeutronPublicInterface}
diff --git a/puppet/controller-puppet.yaml b/puppet/controller-puppet.yaml
index f4eab68aff..49defa9d81 100644
--- a/puppet/controller-puppet.yaml
+++ b/puppet/controller-puppet.yaml
@@ -262,6 +262,10 @@ parameters:
     type: string
     hidden: true
     default: ''  # Has to be here because of the ignored empty value bug
+  NeutronExternalNetworkBridge:
+    description: Name of bridge used for external network traffic.
+    type: string
+    default: 'br-ex'
   NeutronBridgeMappings:
     description: >
       The OVS logical->physical bridge mappings to use. See the Neutron
@@ -697,6 +701,7 @@ resources:
                 - "','"
                 - {get_param: NeutronNetworkVLANRanges}
         neutron_bridge_mappings: {get_param: NeutronBridgeMappings}
+        neutron_external_network_bridge: {get_param: NeutronExternalNetworkBridge}
         neutron_public_interface: {get_param: NeutronPublicInterface}
         neutron_public_interface_raw_device: {get_param: NeutronPublicInterfaceRawDevice}
         neutron_public_interface_default_route: {get_param: NeutronPublicInterfaceDefaultRoute}
@@ -957,6 +962,7 @@ resources:
                 neutron::server::auth_uri: {get_input: keystone_auth_uri}
                 neutron::server::identity_uri: {get_input: keystone_identity_uri}
                 neutron::server::database_connection: {get_input: neutron_dsn}
+                neutron::agents::l3::external_network_bridge: {get_input: neutron_external_network_bridge}
                 neutron::agents::ml2::ovs::enable_tunneling: {get_input: neutron_enable_tunneling}
                 neutron::agents::ml2::ovs::local_ip: {get_input: neutron_local_ip}
                 neutron_flat_networks: {get_input: neutron_flat_networks}