[Wolves] Funny happenings with LTSP

Mark Ellse me at chaseacademy.com
Wed Mar 9 17:21:00 UTC 2011


Many thanks for these suggestions.

Can you manually examine the config on the switch? It's possible there
> is some residual config left somewhere, perhaps the use of VLANs which
> restrict access to certain switch ports.

I can. And I have done. There doesn't seem to be anything causing a problem.
And since I've tried two switches, it would be highly coincidental with them
both stopping the same thing. And if I connect to the same port of the
managed switch that doesn't work with a client, via a normal dumb switch,
LTSP works fine.

> Other than that, Gb ethernet uses all 4 pairs on an ethernet cable,
> unlike 10 and 100 MB, which only use 2 pairs. As a result, as Alex
> suggested, 100 Mb will often work on cables with broken pairs, where Gb
> ethernet exposes the fault and won't work.

I take this point. But the ports that I am trying to use are the 100M ports.

The only other thing I can think is maybe your clients are failing to
> auto-negotiate the speed setting when 1GB is available.

When my daughter suggested this, I thought it the most likely issue. It does
seem to be almost something at a hardware level since putting a dumb switch
between the non-working client and the managed switch makes the client work.
So, obviously, everything necessary is getting through the managed switch.

I also thought that it couldn't be a problem with spanning tree, which I did
try disabling, but it made no difference. If spanning tree had been a
problem, it would have been so even with the dumb switch in place.

The managed switch ports were initially set to auto and I moved them to 100M
to check the issue of negotiation. No improvement.

> This seems
> unlikely to be honest but you could check it by booting your thin
> clients from a live CD or USB stick and using ethtool when attached to
> the Gb switch, e.g.:
ethtool eth0
> It's possible that you might need to install ethtool inside the live CD
> environment depending on what you use, which is do-able but not when
> your switch doesn't work ;)
> This is a good idea. There are one or two ideas to try first, but I'll put
this on the list.

I am going to try a different network card and see if it is a problem with
the onboard NIC.

After that I am scratching around. (LTSP does not like blue? The managed
switch is blue. Try painting the managed switch the same colour as the dumb

The bottle of champagne is still going.

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