How to Enable Logging in Iptables on Linux

Enabling logging on iptables is useful for observing traffic coming to our server. This way we can also find out the number of hits done from any ip. This article will help to enable loging in iptables. Previously we have learned how easy it is to install and use iptables on CentOS, you can get that basic information on my previous tutorial.Enable Iptables LOG

We can simply use following command to enable logging in iptables.

$ iptables -A INPUT -j LOG

We can also define the source ip or range for which log will be created.

$ iptables -A INPUT -s -j LOG

To define level of LOG generated by iptables us –log-level followed by level number.

$ iptables -A INPUT -s -j LOG --log-level 4

We can also add some prefix in generated Logs, So it will be easy to search for logs in a huge file.

$ iptables -A INPUT -s -j LOG --log-prefix '** SUSPECT **'

View Iptables LOG

After enabling iptables logs, you can check the following log files to view logs generated by iptables as per your operating system.

On Ubuntu and Debian

iptables logs are generated by the kernel. So check following kernel log file.

$ tailf /var/log/kern.log

On CentOS/RHEL and Fedora

# cat /var/log/messages

Change Iptables LOG File Name

To change iptables log file name edit /etc/rsyslog.conf file and add following configuration in file.

kern.warning /var/log/iptables.log

Finally restart rsyslog service using following command.

$ service rsyslog restart