Having no luck monitoring NTP

asked 2026-04-06 18:34:05 +0000

Hello. I am working on an IoT device based on an Adafruit Feather with a Wiznet W5500 Ethernet breakout board. It is running an SNTP client that only gets a response for its first request. I am trying to use Wireshark to figure out what is going on but am not getting any output related to the device.

I have tried:

  • port 123 capture filter
  • ip.host display filter
  • ethernet filters

The port 123 filter did capture an NTP request/response from my Mac.

Environment:

  • MacPro, MacOS 15.5
  • Wireshark 4.6.4
  • The Mac and the Feather are plugged into the same Ethernet switch

Note that Wireshark does not capture either the request or the response for the first request.

I know that the W5500 is functional because I do get a response first request and at startup the device also makes an HTTP request and gets and displays the response as expected.

TIA, D.

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Comments

See the "Switched Ethernet" section of the Ethernet capture setup page om the Wiki.

It's not clear if there is another connection on the switch out to the Internet or if Mac is the destination for all of the requests.

Chuckc gravatar imageChuckc ( 2026-04-06 19:53:12 +0000 )edit