RHEL and CentOS 7 use firewall-cmd instead of iptables. You should use that kind of command:
# add ssh port as permanent opened port firewall-cmd --zone=public --add-port=22/tcp --permanent
Then, you can reload rules to be sure that everything is ok
This is better than using iptable-save, espacially if you plan to use lxc or docker containers. Launching docker services will add some rules that iptable-save command will prompt. If you save the result, you will have a lot of rules that should NOT be saved. Because docker containers can change them ip addresses at next reboot.
Firewall-cmd with permanent option is better for that.
Check “man firewall-cmd” or check the official firewalld docs to see options. There are a lot of options to check zones, configuration, how it works… man page is really complete.
I strongly recommand to not use iptables-service since Centos 7