Having used only ISP-provided bandwidth monitors in the past, I’d never set one up myself and didn't know how bandwidth monitors actually gather the data they use to display their traffic graphs and statistics. Unfortunately, the bandwidth monitor that my company’s ISP uses shows information only for the Internet connection at our main location; we recently needed data for all 21 locations before committing to a private network upgrade. A consultant friend recommended Paessler's PRTG Traffic Grapher.

This valuable tool supports SNMP monitoring via SNMPv1, SNMPv2, and SNMPv3; Cisco Systems’ NetFlow protocol, packet sniffing (which provides data about applications and devices), or latency (which uses ICMP to identify overloaded devices or network segments). Paessler’s recommendation for PRTG Traffic Grapher is to use SNMP in most cases, or NetFlow for large or traffic-heavy Cisco networks. To use the packet sniffing sensor, you must plug into a switch’s monitoring port or install PRTG Traffic Grapher on a computer acting as a router between the subnets you want to monitor. In addition, Windows Server 2008 doesn’t support the packet sniffing sensor.

PRTG Traffic Grapher’s system requirements are pretty loose. According to the company’s website, Windows XP or later, either 64-bit or 32-bit, will work. Hardware-wise, you need a server, PC, or virtual machine (VM) with the equivalent performance of an average computer built in 2007. To view the PRTG Traffic Grapher web console, you need Internet Explorer 8.0, Google Chrome, Mozilla Firefox, or Apple’s Safari. In my testing, I installed the product on Windows Server 2008, Windows Vista, and XP without any problems.

To install PRTG Traffic Grapher, simply download the executable file from Paessler’s website and run it on a Windows client. Along with the desktop application, the software installs a web-based management interface. If you're already running a website on the machine you want to install the software on, you can easily change the port for the PRTG web server in the program options.

Next, you need to decide what interfaces you want to monitor. I wanted to know the amount of bandwidth being used on the WAN and by which sites. We use SonicWall firewalls at each of our 21 locations to form our IPsec VPN. Because our SonicWall devices can all be managed with SNMP, and all site traffic passes though their interfaces, monitoring them would give me the information I needed. I logged on to each device and configured SNMP, pointing to PRTG Traffic Grapher.

Once the endpoint devices are ready to share their SNMP data, you need to configure PRTG Traffic Grapher to collect the data. From the Start menu, select PRTG Traffic Grapher to launch the console application, which Figure 1 shows. In the console’s Data section, select Edit, Add Sensor. Click through the wizard and enter your endpoint device’s IP address when prompted. If PRTG Traffic Grapher can’t communicate with a device via SNMP, the software will prevent you from completing the Add Sensor section. I ran into this problem a couple of times when I forgot to enable SNMP for the SonicWall LAN interface that I wanted to monitor.

PRTG Traffic Grapher

PROS: Minimal installation requirements; easy to install and use; alerts and reports included; inexpensive
CONS: Can't alert by modem in the event of network outage
RATING: 3 out of 5
PRICE: 10 nodes, free; 100 nodes, $380; 500 nodes, $995; 1,000 nodes, $1,595; unlimited nodes, contact vendor
RECOMMENDATION: I recommend the product for anyone working on a network with more than one location or in an environment with a lot of network traffic.

CONTACT: Paessler • +49-911-7872497 • www.paessler.com

Next, you can customize your configuration. You can configure error notification via email, set a limit on your bandwidth graphs to remind you of a particular length’s maximum, set up reports to automatically email at designated times, and so on.

Since installing PRTG Traffic Grapher, I’ve used the program to perform several useful tasks. I gathered all the data necessary to determine the size of circuits we’d need at each location for the network upgrade, identified a device that was being overloaded with network traffic and needed to be replaced, and tracked down a user who decided to plug his personal laptop into the corporate network and start hogging bandwidth.

Even if you have network monitoring in place, you might want to take advantage of PRTG Traffic Grapher’s ability to generate real-time and historical data about traffic usage. The software is easy to set up and use, and the product provides valuable data about networks of any size. I’ve used the trial version for several months, and I plan to purchase the full version so that I can monitor traffic usage at several network points simultaneously.