In case you upgrade your CentOS 6.x box to version 6.4, the shorewall service might complain. With a scary message:
ERROR: Your kernel/iptables do not include state match support. No version of Shorewall will run on this system
This is selinux at work, and the problem can easily be solved by running:
# restorecon -Rv /sbin
Thanks shorewall-users and
Happy hacking,
James
