Experimental Physics and
Industrial Control System

Mark Rivers via Tech-talk <[email protected]> · Sun, 5 Jan 2020 16:45:10 +0000

> Your original message mentions a switch.  Is this still present?  If so, have you checked what link speed is negotiated between this switch an the device?

The switch is always present.  The network path from the Linux machine to the device is as follows:

Linux machine (has both 10 Gbit and 1 Gbit NICs)
      |
10 Gbit switch #1
      |
10 Gbit switch #2
      | (possibly additional 10 Gbit switches in here, I'm not sure)
      |
1 Gbit switch
      |
Device (10 Mbit AUI)

If I use the 1 Gbit NIC on the Linux machine it works fine.  That says to me that the speed negotiation between the 1 Gbit switch and the Device must be working.  It only fails if I use a 10 Gbit NIC on the Linux machine.

> Is the AUI from the early 1990 as well?  As I recall, an AUI is an active device.
> So you might have some luck replacing it with something newer (late 90's).

The AUI is working fine if the Linux machine uses a 1 Gbit NIC.  The packets between the 1 Gbit switch and the device should be independent of what NIC is used on the Linux machine.

> Beyond this, I'm out of ideas.  You might be stuck using an older host to talk to this device.  (30 years is a long time to maintain compatibility)

I don't need an older host, I just need to use the 1 Gbit NIC on my modern Linux host.  I can dedicate that NIC to this device.  It can connect to the same public network with some dummy private IP address, since I will only be using it for this non-IP traffic.  

So I don't have a show-stopper problem, but it does require an additional NIC. I would like to understand why a 10 Gbit NIC gives framing errors given the above network topology that is working fine with a 1 Gbit NIC.

Mark

-----Original Message-----
From: Michael Davidsaver <[email protected]> 
Sent: Saturday, January 4, 2020 11:26 PM
To: Mark Rivers <[email protected]>
Cc: 'Heinz Junkes' <[email protected]>; '[email protected]' <[email protected]>
Subject: Re: Ethernet question

On 1/1/20 10:31 AM, Mark Rivers wrote:
> So the problem appears to be that some frames from the device give “frame” errors on 10 Gbit NICs, whereas they do not on 1 Gbit NICs.  However, some frames from the device do not give frame errors they are received fine even on the 10 Gbit adapters.
> 

Your original message mentions a switch.  Is this still present?  If so, have you checked what link speed is negotiated between this switch an the device?

If not, have you used 'ethtool' to check that the NIC is actually negotiating 10Mbps?

For that matter.  Maybe this dinosaur can't handle full-duplex?

> Any idea what can cause that?

On 1/1/20 9:42 AM, Mark Rivers wrote:
> They are very old devices (early 1990’s).  They are 10-Mbit with AUI connectors. 

Is the AUI from the early 1990 as well?  As I recall, an AUI is an active device.
So you might have some luck replacing it with something newer (late 90's).

I don't suppose you have an old 10Mbps hub around?
I used to have one which I kept to snoop on the device side of a switch I was suspicious of.

Beyond this, I'm out of ideas.  You might be stuck using an older host to talk to this device.  (30 years is a long time to maintain compatibility)

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System