Ethernet problems with 4 wire cabling

Technical Support
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41

Hello, @stefan_e.tx,

Please find the oscillograms below. Measurements were performed without link partner on pair A. The results were the same on pair B. Apalis module is installed on Ixora dev. board.

apalis_pairA.bmp (1.1 MB)
cisco_pairA.bmp (1.1 MB)

Best regards,
Ivan

42

Hi @Ivan_Gorchev

From the Apalis side, the behavior is expected and looks normal. So I wonder if the Switch has some issue establishing the connection? Do the switches support 1Gbit as well? Did you try to force the link speed there? Maybe the switch wants to establish a 1Gbit connection even when only a 4-wire cable is connected.

Regards,
Stefan

43

Hello, @stefan_e.tx,

We performed a lot of tests during the past weeks with different link partners, 2 and 4 pair wires, with and without auto-negotiation.
The Cisco switch had no issues to establish connection with any one of the link partners, except Apalis module. The switch supports gigabit connection for sure, it was tested several times.

The following tests were performed with Apalis module, 4-pair patch and Ixora board as link partner:

  • auto-negotiation is switched off and speed is forced to 100 Mbps from Cisco side, link is established.
  • auto-negotiation is switched on and advertise options are limited to 100 Mbps from Cisco side, link is not established.

We were able to test the Apalis module against HPE 1820 switch too. We faced the same issues with auto-negotiation.

With kind regards,
Ivan

1 Like
44

Hi @Ivan_Gorchev

I tested on my side with an HPE 1820 and it is as you write it is not working out of the box. However, running the command provided by @emanuele.tx solves the issue:

ethtool -s eth0 advertise 0x0f

Did you check that answer? The reason is that both sides try to negotiate 1 GBit/s but this does not work with a 4 wire cable. Therefore, at least one side needs to know that it only can do 100 MBit/s.

45

Hi, @stefan_e.tx,

During all of our tests Apalis module was configured to advertise 100 Mbps with the command, provided by @emanuele.tx.

The only way to get link up against Csico and HPE was to turn off auto negotiation and force speed to 100 Mbps, full duplex.

With kind regards,
Ivan

46

Hi @Ivan_Gorchev

I also tested with a 4 Wire Cable to a HPE 1820 and here it worked fine. Because we can’t reproduce the issue, can you send us your complete setup? I don’t see how else we will find a solution.

Regards,
Stefan