1. MRTG architecture and related components
 

MRTG is a network management application that can monitor any remote network host, which has the SNMP protocol support enabled. MRTG, as a SNMP based application, runs SNMP requests against the target hosts on a regularly basis. 

Originally MRTG was designed to acquire bandwidth information related to the network interfaces on a network host. Currently MRTG can interrogate a host about any supported SNMP OID and construct the variation graph. More than that, the new versions of MRTG are able to extend beyond of SNMP capabilities and collect numerical information from any host that collects and stores this kind of information (for more info on the new capabilities visit the MRTG and RRDTOOL websites). This presentation will focus on the SNMP capabilities of MRTG. 

A network-distributed deployment of MRTG can be represented as follows: 

MRTG acquires the SNMP information performing the following tasks: 

- Interrogates the remote host and gets the value of the specific SNMP OID. 
- Updates the variation graph with the new values and deletes the old graph. The graphs are images in PNG format.  The new variation graph is stored in a location, which can be local or remote on a dedicated MRTG storage server. 
- Stores the new value in the log file. The log file can be located on the local host or remotely on a MRTG storage server. 

The classic version of MRTG builds the graphs immediately after a new SNMP value is acquired and does not store any historical data for future reference. 

The newer version comes with a very flexible database support where historical data can be stored for as long as you configure the database size. MRTG does not generate the variation graphs when a new SNMP value is acquired, just stores it in database, making the whole process faster. The graphical variations are generated "on-demand" using dedicated scripts. 

MTRG requires the following components: 

1. Perl interpreter needs to be installed on the MRTG machine. As MRTG is a Perl written application, it requires the Perl interpreter. A free copy of Perl can be obtained from http://www.activeperl.com/

2. MRTG package. A copy can be downloaded from http://people.ee.ethz.ch/~oetiker/webtools/mrtg/pub/

3. A Web Server is required on the local machine or on a remote machine (distributed installation) in order to make the MRTG graphs available over the web/http. Apache web server comes in free versions for Windows/Linux platforms. A free copy can be downloaded from: http://www.apache.org/