how to find IP if I have MAC address
 

Hi Guys,
I have to find the IP address of a device when I know only the MAC address. Is it possible? The best would be if I can find a bit more - like if it is a computer or printer etc. In this scenario I have only a switch between the devices.
Thanks,
bojo

If you know the range of ip addresses like 192.168.0.1 to 50 you could use this bash script to get a list of ip addresses and matching mac addresses.

Also, it's good to know that the first 3 bytes are manufacturer codes. If you look at this site, it may help you identify whether it's a printer or computer. For instance....
08 00 09 is likely a HP printer.
08 00 09 may be a Matsushita copier/printer.
08 00 37 may be a Fjitsu/Xerox printer of some sort.

http://www.synapse.de/ban/HTML/P_LAY.../P_lay207.html

To run the script, type: sh scanmac 192.168.0.1 192.168.0.50
_____________________________________________________

#!/bin/bash

if [ -z "$1" -o "$1" == "-?" ] ; then
echo "Usage: scanmac starting-ip [ending-ip]"
echo
echo "Will list IP and MAC adresses of all active computers"
echo "within a physical network segment."
echo
echo "If ending-ip is omitted, ending-ip = starting-ip+1"
echo " (so that only the host specified will be scanned)."
echo
echo "If you wish to scan from 192.168.2.1 to 192.168.2.31,"
echo " inclusive, specify ending-ip to be 192.168.2.32."
echo

exit 0
fi

startw=$(echo "$1" | cut -d. -f1)
startx=$(echo "$1" | cut -d. -f2)
starty=$(echo "$1" | cut -d. -f3)
startz=$(echo "$1" | cut -d. -f4)

echo "Starting address: $startw.$startx.$starty.$startz"

endip="$2"

if [ -z "$endip" ] ; then
if [ $startz -eq 255 ] ; then
endz=0

if [ $starty -eq 255 ] ; then
endy=0

if [ $startx -eq 255 ] ; then
endx=0

if [ $startw -eq 255 ] ; then
echo "Sorry, you cannot just scan 255.255.255.255."
echo " Maybe later, or you can try to hack support in."

exit 1
else
endw=$(($startw+1))
fi
else
endx=$(($startx+1))
fi
else
endy=$(($starty+1))
fi
else
endz=$(($startz+1))
fi

endip=$endw.$endx.$endy.$endz
fi

echo "Ending address: $endip"

currentw=$startw
currentx=$startx
currenty=$starty
currentz=$startz

currentip=$currentw.$currentx.$currenty.$currentz

# If the bottom octet is zero, it'll get logged inside the while, so
# don't do it here

if [ "$currentz" -ne "0" ] ; then
echo "$(date): $currentip"
fi

trap "exit 15" 15
trap "exit 2" 2

while [ "$currentip" != "$endip" ] ; do
currentip=$currentw.$currentx.$currenty.$currentz

# another log message whenever the bottom octet rolls over

if [ "$currentz" -eq "0" ] ; then
echo "$(date): $currentip"
fi

ping -c 1 -w 10 $currentip >/dev/null 2>&1

mac=$(arp -a $currentip | cut -d' ' -f4)

case "$mac" in
?incomplete?)
: # do nothing -- no MAC for this IP
;;
entries)
: # again, do nothing -- this is a broadcast address
;;
*)
echo "IP: $currentip -- MAC: $mac"
;;
esac

mac="" # reset for the next loop iteration

# now increment the ip values (w,x,y,z)

if [ $currentz -eq 255 ] ; then
currentz=0
else
currentz=$(($currentz+1))
continue
fi

if [ $currenty -eq 255 ] ; then
currenty=0
else
currenty=$(($currenty+1))
continue
fi

if [ $currentx -eq 255 ] ; then
currentx=0
else
currentx=$(($currentx+1))
continue
fi

if [ $currentw -eq 255 ] ; then
break
else
currentz=$(($currentz+1))
continue
fi
done

thanks a lot
 

it works prety good thanks a lot!

arp -a will list the MAC and ip addresses of other computers on the LAN that your computer has heard reccently.