Common reasons require you to restart Iptables firewall Service
Iptables is firewall service that comes and distributed within Linux OS. In most cases you need to restart Iptables firewall service if you made changes to iptables firewall config file .
How To Restart Iptables firewall Service under Linux / UNIX
The following examples using the restart command in case you want to stop the service you can use stop command and use start command to start stopped service.