UNIX for Advanced & Expert Users

i have 2 files that contains a sorted list of IP addresses.
file_A contains a list of all IPs
file_B contains only around 50% of what is in file_A.

I tried to execute

comm -23 file_A file_B > file_C

to get the difference. My objective is to put all the IPs that are in file_A but not in file_B to file_C.
why am i still getting around 1-2 IPs that are still in file_B? i have sorted both files before executing the comm.

please help.

why not use this script:
for i in `cat fileA`
do
grep $i fileB
if [ $? -ne 0 ]
then
{
echo "$i not present"
#echo $i >> filec
}
fi
done


output can be redirected to the third output file