This is our old Q&A Site. Please post any new questions and answers at


We have a situation that occasionally the poe port speed changes to 10Mhdpx. Upon connection 100Mfdpx is negotiated. As far as I can tell the device speed remains at 100Mfdpx, but the poe port speed changes to 10Mhdpx, which results in massive lossed frames. Can wireshark be used to monitor a port speed and flag when it changes?

regards peter

asked 29 Jan '17, 05:37

pverkaikheemstede's gravatar image

accept rate: 0%

No, that's not possible, as Wireshark cannot capture/read the physical link characteristics. This is something you might be able to monitor on the switch console itself instead.

And it is very improbable that a device and the switch go to different link speeds, because no communication would be possible at all, so it would mean that all frames are lost, not just some. Do you mean 100MBit half duplex maybe?

10HDX is usually a speed a port has when nothing is connected. Duplex mismatch (meaning same speed, but half duplex on one side and full duplex on the other) is very often caused by a misconfiguration, e.g. when setting one side to "auto" and the other to "fixed". More details about that can be found here:

permanent link

answered 29 Jan '17, 05:54

Jasper's gravatar image

Jasper ♦♦
accept rate: 18%

@Jasper I agree. haven´t seen a duplex changing like this. Maybe it is somekind of fracture on the physical wire.

(29 Jan '17, 11:26) Christian_R

The link speed is negotiated only, when the link goes down and up. This happens when the cable is unplugged and replugged OR the port is set to shutdown / no shutdown.

Your best friends are the switch console or the log file from the end device.

permanent link

answered 29 Jan '17, 11:54

packethunter's gravatar image

accept rate: 8%

Your answer
toggle preview

Follow this question

By Email:

Once you sign in you will be able to subscribe for any updates here



Answers and Comments

Markdown Basics

  • *italic* or _italic_
  • **bold** or __bold__
  • link:[text]( "title")
  • image?![alt text](/path/img.jpg "title")
  • numbered list: 1. Foo 2. Bar
  • to add a line break simply add two spaces to where you would like the new line to be.
  • basic HTML tags are also supported

Question tags:


question asked: 29 Jan '17, 05:37

question was seen: 1,338 times

last updated: 29 Jan '17, 11:54

p​o​w​e​r​e​d by O​S​Q​A