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    Thursday, January 30, 2014

    How to log iptables messages in a different log file

    Generally all the info to error level messages are logged inside /var/log/messages but it makes hard to differentiate between long list of logs inside messages.

    To separate the iptables related logs in different file follow the following procedure
    NOTE: For RHEL 6 file name will be rsyslog.conf

    To log all the iptables related messages
    # vi /etc/syslog.conf
    # Log all kernel messages to firewall.log.     
    kern.*                                                          /var/log/frewall.log
    # Log anything (except mail) of level info or higher.
    # Don't log private authentication messages!
    # Don't log kernel related any messages
    *.info;mail.none;authpriv.none;cron.none;kern.none                /var/log/messages

    To log only warning level iptables messages
    # Log all kernel messages to firewall.log.
    kern.warn                                                 /var/log/frewall-warn.log

    To log all the messages for info level to error level
    kern.info;kern.!crit          /var/log/firewall.log
    To log the messages as per their severity level in different files
    kern.*                       /var/log/iptables.log
    kern.crit                    /var/log/iptables-crit.log
    kern.info                    /var/log/iptables-info.log

    For more information on severity levels of syslog follow the below link
    SYSLOG Tutorial

    Once done restart the syslog services
    For RHEL 6
    # service rsyslog restart
    For RHEL 5 or older
    # service syslog restart

    For example
    Q. Create a rule to monitor the ping logs from 192.168.1.10 to the localhost
    # iptables -I INPUT -s 192.168.1.10 -p icmp -j LOG --log-prefix "PING TEST "
    Now let us verify it in our log file

    Try to ping from 192.168.1.10 and observe the log file
    # cat /var/log/iptables.log
    Mar  6 11:22:36 test1 kernel:
    PING TEST IN=eth3 OUT= MAC=00:0c:29:51:aa:e1:00:0c:29:a3:f5:fa:08:00 SRC=192.168.1.10 DST=192.168.1.6 LEN=84 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=ICMP TYPE=8 CODE=0 ID=1037 SEQ=2
    Mar  6 11:23:03 test1 kernel:
    PING TEST IN=eth3 OUT= MAC=00:0c:29:51:aa:e1:00:0c:29:a3:f5:fa:08:00 SRC=192.168.1.10 DST=192.168.1.6 LEN=84 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=ICMP TYPE=8 CODE=0 ID=3341 SEQ=1
    Mar  6 11:23:04 test1 kernel:
    PING TEST IN=eth3 OUT= MAC=00:0c:29:51:aa:e1:00:0c:29:a3:f5:fa:08:00 SRC=192.168.1.10 DST=192.168.1.6 LEN=84 TOS=0x00 PREC=0x00 TTL=64 ID=0 DF PROTO=ICMP TYPE=8 CODE=0 ID=3341 SEQ=2


    Learn how to use iptables in simple steps with examples using below links
    Basic iptables tutorial I
    Basic iptables tutorial II

    Follow the below links for more tutorials:

    What is the difference/comparison between Unix and Linux ?
    What are the maximum and minimum limits for RHEL 4 vs 5 vs 6 ?
    Step by Step Linux Boot Process Explained In Detail
    What is the difference between ext3 and ext4 filesystem in Linux ?
    How to configure Private Network in VMware Workstation
    10 examples to help you understand top command usage in Unix/Linux
    Configure Red Hat Cluster using VMware, Quorum Disk, GFS2, Openfiler
    Tutorial for Monitoring Tools SAR and KSAR with examples in Linux
    15 tips to enhance security of your Linux machine
    Why is Linux more secure than windows and any other OS
    Understanding Load Average in Linux and when to be worried about it?
    Disk Attachment Technology FC vs SAS vs iSCSI
    Understanding UMASK value in Linux
    How to keep a track of all the commands run by any user in Linux
    How do you check Linux machine is Physical or Virtual remotely?

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