Network connection stability issue

Hi, everyone,

Our company has a product called DCU with W5100, and we have faced some network connection stability issue.

When DCU is connected to switch, ping test is not stable for a while and later then completely out.
If we use port forwarding function with router, then the connection is stable.

Please refer the attached summarized document.

We are looking forward to hearing any experience and solution as well.

Thank you.Network Configuration and Stability.pdf (148.0 KB)

You are not the first person experiencing issues with W5x00 + Cisco. Probably Cisco switches are too clever for W5x00, and you must make switch slightly dumber not to drive W5x00 crazy. I bet when your “instability” happens, W5100 continuously flashes its link LED (and also RX LED).

You have two things to try - one of them, or both must improve the situation, or solve your issue:

  1. configure switch’s port into fixed speed - 100 or 10. This way you prevent switch training the line at 1Gb, and thus W5100 should not get issues understanding what is going on seeing its supported waveforms only;
  2. Enable PortFast feature for the port connected to W5100. This will disable line training at all, and in couple with fixed speed setting must make link reliable.


We will ask the network administrator to apply your suggestion.

Thank you so much for your quick response.