Someone

#!/bin/bash

 
isAlive()
{ 
  for i in $*; do
     printf "GET /\n\n" | nc $i 80 > /dev/null 2>&1 && return 0
  done
  return 1
  
}

 gwAuxInUse=false
  
 
while : ; do
  
  isAlive $*
  alive=$?

  if   [ $alive -eq 0 ] && $gwAuxInUse; then
      ip rule del prio 200 table adsl
      ip rule add prio 200 table redUnc
      gwAuxInUse=false
  elif [ $alive -eq 1 ] && ! $gwAuxInUse ; then
      ip rule del prio 200 table redUnc
      ip rule add prio 200 table adsl
      gwAuxInUse=true
  fi       
 
  sleep 10

done