Q.   ntop is a network probe that shows network usage in a way similar to what top does for processes. How do I install latest version of ntop on RHEL 5.x systems?

A.   ntop is a network and traffic analyzer that provides a wealth of information on various networking hosts and protocols. ntop is primarily accessed via a built-in web interface.

Following instructions are tested on 32/64 bit versions only:
a) RHEL Linux 5.x
b) CentOS Linux 5.x

Download latest ntop

Visit   ntop project   to grab latest version. You can use wget to grab the same, enter:
# cd /opt
# wget http://freshmeat.net/redir/ntop/7279/url_tgz/ntop-3.3.6.tar.gz
Untar tar ball, enter:
# tar -zxvf ntop-3.3.6.tar.gz

Configure and Compile ntop under RHEL

You must have   RRDTool installed . You also need to install libpcap, enter:
# yum install libpcap-devel libpcap
Type the following commands to compile and install ntop:
# cd ntop
# ./autogen.sh
Just type make to compile ntop:
# make
Just type make install to install ntop:
# make install
# make install-data-as

Create ntop user

Type the following command to run ntop as ntop user, enter:
# useradd -M -s /sbin/nologin -r ntop

Setup directory permissions

Next, you need to setup directory permissions, enter:
# chown ntop:root /usr/local/var/ntop/
# chown ntop:ntop /usr/local/share/ntop/

Setup ntop user admin password

Type the following command to set ntop admin password, enter:
# ntop -A
Sample output:

      Mon Jul 28 03:38:34 2008  NOTE: Interface merge enabled by default
Mon Jul 28 03:38:34 2008  Initializing gdbm databases
ntop startup - waiting for user response!
Please enter the password for the admin user:
Please enter the password again:
Mon Jul 28 03:38:42 2008  Admin user password has been set
    

Start ntop

Type the following command to start ntop:
# /usr/local/bin/ntop -d -L -u ntop -P /usr/local/var/ntop --skip-version-check --use-syslog=daemon
Sample output:

      Mon Jul 28 03:42:19 2008  NOTE: Interface merge enabled by default
Mon Jul 28 03:42:19 2008  Initializing gdbm databases
    

If you have multiple interface (eth0, eth1 and so on), start ntop as follows:
# /usr/local/bin/ntop -i "eth0,eth1" -d -L -u ntop -P /usr/local/var/ntop --skip-version-check --use-syslog=daemon
Where,

• -i "eth0,eth1"   : Specifies the network interface or interfaces to be used by ntop for network monitoring. Here you are monitoring eth0 and eth1.
• -d   : Run ntop as a daemon.
• -L   : Send all log messages to the system log (/var/log/messages) instead of screen.
• -u ntop   : Start ntop as ntop user
• -P /usr/local/var/ntop   : Specify where ntop stores database files. You may need to backup database as part of your disaster recovery program.
• --skip-version-check   : By default, ntop accesses a remote file to periodically check if the most current version is running. This option disables that check.
• --use-syslog=daemon   : Use syslog daemon.

How do I view ntop stats?

By default ntop listen on 3000 port. You can view ntop stats by visiting following url:
http://localhost:3000/
OR
http://server-ip:3000/

(Fig.01: ntop Global TCP/UDP Protocol Distribution Graphs [click to enlarge])

(Fig.02: Network Load Statistics (click to enlarge])

Open port 3000 using iptables

Open /etc/sysconfig/iptables file, enter:
# vi /etc/sysconfig/iptables
Append following code before final REJECT line:
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 3000 -j ACCEPT
Save and close the file. Restart firewall:
# service iptables restart

How do I view ntop stats without opening port 3000?

Setup simple tunnel using ssh, enter the following on your local UNIX / Linux desktop system:
$ ssh -L 3000:localhost:3000 -N -f user@server.yourcorp.com
Now open browser and type the following command:
http://localhost:3000/

How do I start ntop on boot?

Open /etc/rc.local file, enter:
# vi /etc/rc.local
Append the following line:
/usr/local/bin/ntop -i "eth0,eth1" -d -L -u ntop -P /usr/local/var/ntop --skip-version-check --use-syslog=daemon
Save and close the file.

How do I stop ntop?

Use web interface to shutdown ntop, or use normal kill / killall command:
# killall ntop

Further readings: