diff --git a/devstack/plugin.sh b/devstack/plugin.sh
index 915595a..5d5287a 100644
--- a/devstack/plugin.sh
+++ b/devstack/plugin.sh
@@ -162,6 +162,15 @@ function configure_tobiko_neutron {
     echo_summary "Write [neutron] section to ${TOBIKO_CONF_FILE}"
     local tobiko_conf_file=$1
 
+    if [ -n "${TOBIKO_NEUTRON_EXTERNAL_NETWORK}" ]; then
+        # enable DHCP on IPv4 subnet of external network
+        openstack subnet list --no-dhcp --ip-version 4 -c ID -f value \
+            --network "${TOBIKO_NEUTRON_EXTERNAL_NETWORK}" | \
+            xargs -r -n 1 openstack subnet set --dhcp
+        iniset "${tobiko_conf_file}" neutron external_network \
+            "${TOBIKO_NEUTRON_EXTERNAL_NETWORK}"
+    fi
+
     iniset_nonempty "${tobiko_conf_file}" neutron floating_network \
         "${TOBIKO_NEUTRON_FLOATING_NETWORK}"
     iniset_nonempty "${tobiko_conf_file}" neutron ipv4_dns_nameservers \
diff --git a/devstack/settings b/devstack/settings
index c066400..c84c13d 100644
--- a/devstack/settings
+++ b/devstack/settings
@@ -38,6 +38,7 @@ TOBIKO_KEYSTONE_USER_ROLE=${TOBIKO_KEYSTONE_USER_ROLE:-admin}
 TOBIKO_NOVA_KEY_FILE=${TOBIKO_NOVA_KEY_FILE:-}
 
 # --- Neutron settings ---
+TOBIKO_NEUTRON_EXTERNAL_NETWORK=${TOBIKO_NEUTRON_EXTERNAL_NETWORK:-${PUBLIC_NETWORK_NAME}}
 TOBIKO_NEUTRON_FLOATING_NETWORK=${TOBIKO_NEUTRON_FLOATING_NETWORK:-${PUBLIC_NETWORK_NAME}}
 TOBIKO_NEUTRON_IPV4_DNS_NAMESERVERS=${TOBIKO_NEUTRON_IPV4_DNS_NAMESERVERS:-}
 TOBIKO_NEUTRON_IPV6_DNS_NAMESERVERS=${TOBIKO_NEUTRON_IPV6_DNS_NAMESERVERS:-}