scaning the local network with arping/sh script

[Abu Khaled]

Greetings...

I don't know much about scripting but i tried to write one to scan my
local network using the net/arping port.
here is the script:
<sciprt start>
#!/bin/sh
IP=1
while [ $IP -le 20 ]
do
echo -e ".\c"
   if ( arping -c 1 -q -i rl1 10.0.0.$IP ) then
      echo -e "\n10.0.0.$IP Online"
   fi
IP=$(( $IP +1 ))
done
echo -e "\n"
<script end>

The script runs and reports OK but it is very slow and takes a lot of
time to scan a large network. Does anyone have an idea on how to
improve it or provide an alternate way to do it?

PS: I used the arpscan port in the past but it is reported as broken:
Unfetchable.
      I'm running FreeBSD 5.4 Stable.

-- 
Kind regards
Abu Khaled