When firewall is running, The local computer (the computer where the firewall is

Question

When firewall is running, The local computer (the computer where the firewall is running) can (5) Ping other computers on the local network; (6) Remotely log into (e.g., ssh) other computers on the local network; (7) Visit web servers on remote networks (e.g., www.google.com). The local computer cannot (8) Ping other computers on remote networks (e.g., ping www.google.com); Make sure to choose a remote computer which is not behind a firewall blocking incoming ping messages. (9) Traceroute a computer on remote networks (e.g., traceroute www.yahoo.com). Other computers on the local network cannot (10) Ping the local computer; (11) Remotely log into (e.g., ssh) the local computer. need to configure firewall that can do these things with iptables

Explanation / Answer

A firewall in IT terms is a software or hardware solution which tries to block as much as possible evil network traffic, while allowing usefull traffic. Firewalls can be either implemented in existing network devices like routers, as separate devices with the sole function to protect a network or in the first layers of the networking stack on a networked computer

Iptables is a software solution which is available on most Linux computers with a kernel version 2.4 or newer. To be honest we have to say that iptables is not the firewall itself. The iptables program is a frontend which can be called from the command line to alter filter tables in the kernel. The real firewall is present in the kernel. Because most people will only use the iptables program, it is often referred to as the Linux firewall and we will do it here also for convenience.

Loading the iptables settings

On RedHat family Linux distributions the configuration of the system which must be loaded at startup is stored in the /etc/sysconfig directory. The file iptables contains a list of rules for the firewall. The framework of our firewall looks like

for more info please visit below links

http://www.thegeekstuff.com/scripts/iptables-rules

http://www.thegeekstuff.com/2011/06/iptables-rules-examples/

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