My internet provider has provided me a Fritz!Box Fon 3970, which is a neat all-in-one modem / router / voip and DECT connectivity box. Although this box is running Linux and pretty extendible with Freetz, in some area’s it is a pretty closed black (erm.. red) box and sometimes it is hard to debug problems.
Today, while debugging issues with my DHCP server, I found out that the standard Fritz!Box firmware includes a handy network tracer. To trace network traffic (all or just on a specific interface), go to http://fritz.box/capture.lua and specify which interface to start the trace on.
The output will be provided through a download that starts immediately. The resulting file can be opened using Wireshark for analysis.
I didn’t solve my DHCP problem yet (the DHCP server is still only giving WLAN clients and IP address and not to wired clients), but that’s something I will tackle over the weekend now that I can obtain a decent network trace from the box.