[a] Apache

[b] PHP 5

[c] php-gd extension

You can install all of the above softwares using the yum command:
# yum install httpd php php-gd
Configure httpd service as per your requirements:
# vi /etc/httpd/conf/httpd.conf
Turn on the httpd service:
# chkconfig httpd on
# service httpd start
# netstat -tulpn | grep :80

Download vnStat php frontend

Visit this url and grab the latest version using the wget command:
$ cd /tmp
$ wget http://www.sqweek.com/sqweek/files/vnstat_php_frontend-1.5.1.tar.gz
Untar or extract the tarball (tar file) called vnstat_php_frontend-1.5.1.tar.gz, type:
$ tar xvf vnstat_php_frontend-1.5.1.tar.gz

Install vnStat php frontend

You need to install this frontend at the following location:
/var/www/html/vnstat/
Make a directory called /var/www/html/vnstat/ using mkdir command:
# mkdir -p /var/www/html/vnstat/
Copy files from /tmp/vnstat_php_frontend-1.5.1 to /var/www/html/vnstat using cp command, enter:
# cp -av /tmp/vnstat_php_frontend-1.5.1/* /var/www/html/vnstat
If you are using SELinux, restore file(s) default SELinux security contexts using restorecon command:
# restorecon -Rv /var/www/html/vnstat/

Configure vnStat php frontend

You need to edit /var/www/html/vnstat/config.php, enter:
# vi /var/www/html/vnstat/config.php
You need to edit this file to reflect your particular situation. First, set language to en:

$language = 'en';

I am monitoring eth0 and eth1. So list of network interfaces monitored by vnStat should be set using the following:

$iface_list = array('eth0', 'eth1');

You can set names for interfaces:

$iface_title['eth0'] = 'Internal';
$iface_title['eth1'] = 'External';

Save and close the file.

How do I view graphs?

Fire a web browser and type the url:

http://your-server-ip-address-here/vnstat/
http://localhost/vnstat/
http://server1.cyberciti.biz/vnstat/
http://192.168.1.100/vnstat/

Sample outputs:

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