Max MTU Size

#!/bin/bash

# Pass a starting mtu size and an ip address/host name
#./mtusize.sh 1430 www.google.co.uk

maxmtu=$1
dest=$2

while true;
do
  ping -s $maxmtu -c 3 -M do $dest
  if [ $? -ne 0 ] ; then
    let maxmtu=maxmtu-1
    break;
  fi
  let maxmtu=maxmtu+1
done

let finalMTU=$maxmtu+28
echo "Last working MTU was $finalMTU octets; ($maxmtu octets + 8 octet ICMP header + 20 octect IP header)"