--- vpnc-script.orig	2013-09-11 16:42:41.657485918 +0400
+++ vpnc-script	2013-09-11 16:48:49.605289870 +0400
@@ -97,7 +97,8 @@
 	if [ -n "$INTERNAL_IP4_MTU" ]; then
 		MTU=$INTERNAL_IP4_MTU
 	elif [ -n "$IPROUTE" ]; then
-		MTU=$(($($IPROUTE route get "$VPNGATEWAY" | sed -ne 's/^.*mtu \([[:digit:]]\+\).*$/\1/p') - 88))
+		R_IFACE=`$IPROUTE -o route get "$VPNGATEWAY" | sed -e 's/.*[0-9] dev \([[:graph:]]\+\).*$/\1/'`
+		MTU=$(($($IPROUTE -o link show "$R_IFACE" | sed -ne 's/^.*mtu \([[:digit:]]\+\).*$/\1/p') - 88))
 	else
 		MTU=1412
 	fi