#!/bin/sh
[ "$1" = "" ] && echo "usage: $0 <route-prefix> # to list all double routes starting with route-prefix" && exit

string=$(for addr in `/sbin/route -n | grep ^$1| sort | awk -F ' ' '{print $1}'` ; do [ "$oldaddr" != "$addr" ] || echo -n "^$addr\\|"; oldaddr=$addr; done ;echo -n "nix")

/sbin/route -n | grep "$string"