Starting from firmware version all the Snom Desktop phones equipped with one or more USB ports can store PCAP traces on a mass-storage device connected via USB. In this case the trace size is limited to the USB device free space only.

In order to enable this feature you need to

  • enable the usb_storage_pcap phone setting
  • create a flag file named pcap.flg on the USB device root directory
  • plug the USB device into the phone`
Step-by-step guide:

  1. Enable the usb_storage_pcap: you can do it via provisioning or via phone web interface clicking on Advanced -> QoS/Security:

  2. Create the "flag file" pcap.flg into the root directory:

  3. Plug the USB device into the phone USB port, the phone should detect the storage device:


  4. At this point the phone starts saving the pcap trace on the USB device, once you reproduced the issue you can unmount and unplug the USB device. Unmounting the device before unplugging is fundamental in order to avoid data corruptions.
    The USB device can be un-mounted pressing the Menu key, selecting Maintenance and then Unmount USB disk:

  5. Now your are ready to plug the USB device into your computer and start analysing the saved PCAP trace:

Be aware that in heavy network load scenarios some packets can be missing from the saved PCAP trace. In this case the best way to obtain a trace is using a network hub or a switch port mirror.