ping_site="8.8.8.8"
 ntp_server="pool.ntp.org"
 net_isolation_enabled="TRUE"
+net_isolation_arg=""
 post_config="TRUE"
 debug="FALSE"
 
             ;;
         --flat )
                 net_isolation_enabled="FALSE"
+                net_isolation_arg="--flat"
                 echo "Underlay Network Isolation Disabled: using flat configuration"
                 shift 1
             ;;
 
                               default='network-settings.yaml',
                               dest='net_settings_file',
                               help='path to network settings file')
-    net_settings.add_argument('-i', '--network-isolation', type=bool,
+    net_settings.add_argument('--flat', action='store_false',
                               default=True, dest='network_isolation',
-                              help='network isolation')
+                              help='disable network isolation')
     net_settings.add_argument('-e', '--net-env-file',
                               default="network-environment.yaml",
                               dest='net_env_file',
                               default='network-settings.yaml',
                               dest='net_settings_file',
                               help='path to network settings file')
-    nic_template.add_argument('-i', '--network-isolation', type=bool,
+    nic_template.add_argument('--flat', action='store_false',
                               default=True, dest='network_isolation',
-                              help='network isolation')
+                              help='disable network isolation')
     nic_template.add_argument('-n', '--enabled-networks', required=True,
                               dest='enabled_networks',
                               help='enabled network list')
 
       ovs_dpdk_bridge=''
     fi
 
-    if ! controller_nic_template=$(python3.4 -B $LIB/python/apex_python_utils.py nic-template -r controller -s $NETSETS -i $net_isolation_enabled -t $CONFIG/nics-template.yaml.jinja2 -n "$enabled_network_list" -e "br-ex" -af $ip_addr_family); then
+    if ! controller_nic_template=$(python3.4 -B $LIB/python/apex_python_utils.py nic-template -r controller -s $NETSETS $net_isolation_arg -t $CONFIG/nics-template.yaml.jinja2 -n "$enabled_network_list" -e "br-ex" -af $ip_addr_family); then
       echo -e "${red}ERROR: Failed to generate controller NIC heat template ${reset}"
       exit 1
     fi
 
-    if ! compute_nic_template=$(python3.4 -B $LIB/python/apex_python_utils.py nic-template -r compute -s $NETSETS -i $net_isolation_enabled -t $CONFIG/nics-template.yaml.jinja2 -n "$enabled_network_list" -e $ext_net_type -af $ip_addr_family -d "$ovs_dpdk_bridge"); then
+    if ! compute_nic_template=$(python3.4 -B $LIB/python/apex_python_utils.py nic-template -r compute -s $NETSETS $net_isolation_arg -t $CONFIG/nics-template.yaml.jinja2 -n "$enabled_network_list" -e $ext_net_type -af $ip_addr_family -d "$ovs_dpdk_bridge"); then
       echo -e "${red}ERROR: Failed to generate compute NIC heat template ${reset}"
       exit 1
     fi