add_tagged_dev_ns () {
     NETNS=$1
     IP=$2
     VLAN=$3
     sudo ip netns exec $NETNS ip link add link veth0 name veth0.${VLAN} type vlan id $VLAN
     sudo ip netns exec $NETNS ip link set dev veth0.${VLAN} up
     sudo ip netns exec $NETNS ip addr flush dev veth0
     sudo ip netns exec $NETNS ip addr add dev veth0.${VLAN}  $IP
 }
