Control Network Newsletter

Using the Skorpion Diagnostic Switch with Wireshark®

July 2011 - One benefit of switched Ethernet technology is that the switch restricts directed messages to only those ports party to the communication. This improves overall network throughput by not burdening end stations with useless traffic. However, this feature makes protocol debugging difficult because a network protocol analyzer tool, like the free, open-source Wireshark, attached to an unused port on the switch cannot observe any directed messages on other ports. In the past, the solution was to change out the switching hub with a repeating hub – but with the Skorpion Diagnostic Switch this is unnecessary.

The Skorpion Diagnostic Switchretains all the virtues of switched Ethernet technology (including Auto-MDIX and auto-negotiation) but with one exception – no address learning. Thus, all messages (directed, multicast, broadcast) are floodedto all switch ports so that network sniffers such as Wireshark can be used to observe all network traffic that passes through the switch. The switch can be permanently installed or carried from one site to another as needs arise. It can be used for control panel installations if you need the ability to diagnose problems in the field. It can also be used in a development environment when debugging code.

The Wireshark.org website claims that Wireshark is the world's foremost network protocol analyzer. It lets you capture and interactively browse the traffic running on a computer network. It supports hundreds of protocols including BACnet thanks to the numerous individuals who support the Wireshark open-source application. It can work with both wired and wireless networks. It is extremely handy when troubleshooting tough network problems as long as you can capture the traffic of interest. With switched Ethernet this can be a problem and that is where the Diagnostic Switch comes into play.

Using the Skorpion Diagnostic Switch with Wireshark calls for some special considerations that are discussed in a recently published Application Note. Topics include:

• Installing the Diagnostic Switch Temporarily
• Installing the Diagnostic Switch Permanently
• The Diagnostic Switch and Embedded Peer-to-Peer Devices
• The Diagnostic Switch in a Cascaded Switch Network

Download the application note (PDF) to learn more.