Understanding Firewall configurations

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Understanding Firewall configurations

Install iptables package

Before starting, we must make sure that iptables RPM installed. The iptables RPM is there in RedHat Linux installation CD #2. The file name generally starts with software package name with its version name as this:

iptables-1.2.11-3.1.RHEL4.i386.rpm.

Starting iptables

We can start, stop, and restart iptables after booting the system using the following commands:

# service iptables start

# service iptables stop

# service iptables restart

Firewalls

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Firewalls:

Data direction in iptables: This command is based on controlling data traffic in three directions: IN, OUT and THORUGH. That is, we can configure our iptables to stop data from entering into our LAN from outside network, stop data from leaving our computer, and control the data that travels forward between LAN and the internet.

Chains in iptables: Most of the firewalls are based on series of iptables commands. These commands are connected as chains. The RedHat Linux saves firewall commands in /etc/sysconfig/iptables file.

Pluggable Authentication Modules (PAM)

These modules are used to limit access to specific application, as redhat-config-network or reboot, to the root user itself. Different PAM modules let us control access by password, by access location or by user.