config problem - not seeing all messages

[Ron W <ronw.mrmx () gmail com>]

I am trying to use WireShark to diagnose a network problem between a
Windows PC and a Linux-based controller (for a robot).

The controller uses uboot and TFTP to download the Linux image from the PC.
Using the controller's serial port, I can see the messages output by uboot
and by Linux. The messages as as expected and the controller appears to
work correctly except after downloading Linus via TFTP, the PC application
is not able to communicate with the controller via TCP/IP.

So, I connected an Ethernet switch between the PC and the controller and
also connected a laptop to the switch so I can monitor with WireShark.

What I see in WireShark's capture log (see attached screen picture) would
have made sense, but the log is not showing the TFTP messages. So, to make
sure TFTP was actually working, I interrupted uboot before it started
downloading Linux. I then entered commands to have uboot download various
test files I created and inspect what was downloaded to make sure the
expected content was in the controller. As I did this, I continued to
monitor with WireShark. Still I did not see anything after the initial ARP
request from the controller, asking for the MAC corresponding to the IP
address of the PC. i did not even see an ARP reply from the PC.

Since I'm not seeing the TFTP messages, nor the PC's ARP response, I have
to assume I configured WireShark incorrectly. Looking at my capture
selection and capture options (see attached screen pictures), I can't find
anything to explain not seeing the TFTP messages in the capture log.

I even tried a fresh install of WireShark on another laptop that had never
had Wireshark on it. Same result: No TFTP message in the capture log.

I have used WireShark successfully in the past. As best I can remember, I
setup WireShark the same as I have in the past.

Still, I must be doing something wrong. Any advise on what I need to fix in
my WireShark settings?

Thanks in advance

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