diff --git a/files/qemu-ifup b/files/qemu-ifup
index c8051a9..cd85457 100755
--- a/files/qemu-ifup
+++ b/files/qemu-ifup
@@ -6,6 +6,10 @@ if [ ${#IFACE} -gt 15 ]; then
    echo "interface name too long, mac 14 char: $IFACE"
    exit 10
 fi
+if [[ ${0##*/} == qemu-ifup-* ]]; then
+   PARENTIF="${0##*-}"
+   echo "legacy VLAN trunk mode using $PARENTIF as uplink"
+fi
 
 VNI=$(printf '%d' $((16#${IFACE##*.})))