+ [ "$iface6rd" != 0 -a -f /lib/netifd/proto/6rd.sh ] && append dhcpopts "-O 212"
+ [ -n "$zone6rd" ] && proto_export "ZONE6RD=$zone6rd"
+ [ -n "$zone" ] && proto_export "ZONE=$zone"
+ [ -n "$mtu6rd" ] && proto_export "MTU6RD=$mtu6rd"
+ [ -n "$customroutes" ] && proto_export "CUSTOMROUTES=$customroutes"