A. For one-off switching disabling firewall in Linux:

1. Login to terminal as 'root' user.

2. Issue following command:

$ service iptables stop

B. To disable firewall at the time of boot itself:

1. Login to terminal as 'root' user.

2. Issue following command:

chkconfig iptables off

Environment

The above commands were tested on Oracle Linux 5.7 and 6.5