Use your favorite text editor:
vi /etc/sysconfig/iptables
This is how you ALLOW access to a range of IP addresses:
# 211
-A RH-Lokkit-0-50-INPUT -p tcp -m state –state NEW,ESTABLISHED -s 64.1111.222.0/24 –dport 22 -j ACCEPT
-A RH-Lokkit-0-50-INPUT -p tcp -m state –state NEW,ESTABLISHED -d 64.111.222.0/24 –sport 22 -j ACCEPT
***********************************************************
by default, everybody should be locked out of the box
- DO NOT FORGET THIS STEP - BE CAREFUL - DO NOT LOCK YOURSELF OUT (SEE ABOVE)
-A RH-Lokkit-0-50-INPUT -p tcp -m tcp –dport 22 -j REJECT
***********************************************************
This is how you lock up certain ports
#shut out these imap hackers
-A RH-Lokkit-0-50-INPUT -p tcp -m state –state NEW,ESTABLISHED -s 66.44.77.33 –dport 993 -j REJECT
-A RH-Lokkit-0-50-INPUT -p tcp -m state –state NEW,ESTABLISHED -d 66.44.77.33 –sport 993 -j REJECT
Now restart the service
/etc/init.d/restart