Shell Programming and Scripting

while read ip
do
   echo $ip
done < ip_list

while read ip (while read is a linux script ? ip is there any significance to internet protocol?
do (ok do the following scripts twice)
  check_GE-VLANStats-P3 $ip (then echo to my variable $ip)
  check_GE-VLANStats-P3 $ip
done < ip_list

cat ip_list | while read IP
do
..
done

#
# this is in sh
#

for ip in `cat ip_list`
do
    check_GE-VLANStats-P3 $ip
    check_GE-VLANStats-P3 $ip
done

#
# this works in bash and ksh
#

for ip in `< ip_list`
do
    check_GE-VLANStats-P3 $ip
    check_GE-VLANStats-P3 $ip
done