Auto-negotiation Mismatch on HP2524

[dm993]

Hi Guys,

I have an HP2524 procurve switch connecting to an industrial controller (Watlow).

The port speed & duplex of the industrial Watlow device cannot be configured (really annoying) it is set to Auto Negotiate by default and is capable of 10Mbps Hdx, or 100Mbps Hdx.

I have never seen this happen anywhere before but, the Watlow is reporting as 100Mbps Hdx, the HP2524 switch port is 10Mbps Hdx.

A big problem is that sometimes the physical link is up but comms stop and the cable needs unplugged and reconnected (or the switch port disabled/re-enabled).

I have no control over the use of this Watlow device, the link is up and working (but with packet loss) - does anyone have any suggestions?

[BUPA IS]

Hello,
The auto negotiate loop has not completed and the ends of the link do not quite know what they are supposed to do.
Try setting the switch end to 100 Half duplex, with auto negotiate off and ignore the fact that the device end is unchangable. This will match the current setting of the remote device and limit the options of auto negotiate in it.

I hope this is of some help
Mike

[dm993]

I may have already tried that, but before I knew that the Watlow was only capable of half-duplex transmissions, I may have selected 100 full, so will give it another try to see if it works any better.

Would it make sense that autonegotiation fails due to possible interruptions on the link from broadcast/multicast packets, there are a lot of these on this switch and I have not yet configured IGMP snooping, it is VLANd as far as it can be for the moment,

thanks for your response,
Dave

[BUPA IS]

No at the moment I do not think that the lan traffic is causing your problem. The speed mismatch and possibly an intermittent duplex mismatch is the primary problem to be solved.
Fixing the settings with auto off in the switch will give the Watlow device only one choice.

This kind of problem is often caused by different manufacturers interpreting the 10/100 autonegotiate rules in a slightly different fashion causing one end of the link to fail back to 10 half and the other to keep trying to negotiate up to 100Full if possible, so leading to the constant up / down effects. If you are lucky both ends will settle on 10half which works but tends to be slow.

Mike

[rick jones]

Speed is detected by autosense, duplex is done by autoneg, but I think many places lump the two together.

If the watlow can only do half-duplex, it may not even know how to autonegotiate. In that case the side trying to autoneg will "fail" and it should fall into half-duplex operation.

If one end of the cable shows 10 Mbit/s and the other shows 100 Mbit/s and you actually have traffic flowing through,one side or the other is lying about the speed - there is no way to have different speeds on opposite ends of the same cable (not that I've ever known anyway...)

Industrial device - are there lots of sources of electrical "noise" around? Is everything well grounded? Do you *know* the cable you are using is a good one and not possibly marginal? You might try a shorter or longer cable - there were issues in the "old days" of 100BT phys with "problems" with certain lengths of cable. Your description makes it sound like the Watlow is from that era.