Every wireless troubleshooting story starts with a user complaint: “There’s a problem with the WiFi.” (Although sometimes the complaint is in more colorful language.) Here’s how we easily solved one issue using Mojo Packets, our online troubleshooting tool (formerly called WizShark), and busted the myth that stationary clients don’t roam.
A user of our wireless network had poor connectivity. The case was reported to the network administrator, who performed a packet capture of the environment. The pcap file was uploaded to Mojo Packets, which processed it and presented a visual dashboard that enabled a quick drill-down to the issue.
Network Health at a Glance
One glance at the Client Connectivity Health Classification chart revealed that out of five clients in the network, four were healthy (green) and one was suffering from connectivity issues (red).
Auto-Identifying the Client
The MAC address of the unhealthy client popped up automatically in the bar graph titled Top Clients by Connectivity Failures, and was auto-analyzed for failure types and their counts. Clicking on this bar triggers a filter on the table at the bottom, showing only this client.
Filtering Down to the Culprit Frames
Mojo Packets represents all the packets the client has sent or received as colored points on a graph of frame numbers (X-axis) and frame types (Y-axis). (Click here for a hands-on demo.) Lower means a weaker client connection to the AP (e.g. beacons or probes), and higher means a stronger connection (e.g. EAP or data). Thus a frequent zigzag on the graph indicates an unstable connection: exactly what this client reported.
At first, the graph is crowded with brown triangular bullets indicating Data and Null packets. Those can be filtered out with the Frame Filter. Just uncheck them and refresh.
Visual Troubleshooting at the Frame Level
Now it’s easier to see various management packets forming the ups and downs on the graph, indicating a not-so-smooth connection. After zooming in, various yellow star bullets stand out, indicating reassociation packets: reconnections between the client and the AP.
The tooltips for these yellow star bullets give the relevant information for the reassociation frames, especially the fields Current AP and Destination.
Such aggressive roaming by the stationary client was the reason for the poor WiFi connectivity experienced by the user. Clearly a stationary client can roam between APs — an insight which enabled us solve the issue by reducing the driver sensitivity.