How to Check if IP is blocked:
  [root@server ~]# iptables -L -n –line | grep [IP Address]
If IP appear as DROP or REJECT, the IP has been blocked

Unblock the IP Address:

[root@server ~]# iptables -I INPUT -s [IP Address] -j ACCEPT

Blocking back an IP Address:

[root@server ~]# iptables -A INPUT -d [IP Address] -j DROP

After adding or removing ips from iptables you need to save iptable rule using following command.

[root@server ~]# service iptables save

After that restart to iptables

[root@server ~]# service iptables restart

How to start, stop and check the status

[root@server ~]# service iptables start
[root@server ~]# service iptables stop
[root@server ~]# service iptables restart

How to take backup and restore IPtables Rules

[root@server ~]# iptables-save > /root/working.iptables.rules

To restore it use the command iptables-restore, enter:

[root@server ~]# iptables-restore < /root/working.iptables.rules

Reinstall IP tables

[root@server ~]# yum reinstall iptables