On Wed, 2011-01-26 at 08:40 -0500, Olin Lathrop wrote:
> Herbert Graf wrote:
> > Yes, I've seen several 10/100 switches that work
> > "strangely" when you plug a 10Mbps in. The ones most prominent problem
> > switch in my memory sent duplicate packets (everything the 10Mbps
> > device sent ended up on the wire after the switch twice).
>=20
> But you also said this was at half duplex.  There is absolutely no point =
to
> half duplex when you have separate transmit and receive channels, like yo=
u
> do with all modern ethernets.  Some switches just assume everything is fu=
ll
> duplex, and then half duplex devices act strangely.  This is a duplex iss=
ue,
> not a 10/100 issue.

Yes, because the first stage of narrowing the problem was to switch
things to half duplex (the problem was first noticed when the device was
enabled for full duplex). Changing the switch to half duplex didn't
solve the problem.=20

The worst switch I saw this behaviour with did the same thing whether
the device was full or half duplex (some switches with problems were
cleared up if I set the port to half duplex), whether the port was set
to full or half duplex, and was the same between multiple DIFFERENT
10Mbps devices. It was CLEARLY an issue with that switch at 10Mbps
(forcing a PC to 10Mbps produced the problem, switch the PC back to
100Mbps and the problem disappeared).

Again, there is ZERO doubt that this switch (I tried multiple switches
of the same model) has a design flaw, but all it takes is for your
customer to be using a switch like it and all of a sudden YOUR product
is at fault, since nothing else plugged into that switch seems to have a
problem.

Fact is, the ethernet world is leaving 10Mbps behind (at the moment with
switches that have obvious bugs at 10Mbps), and it would be wise to
consider switching your designs to 100Mbps (unless there's an overriding
reason not to, other then "I don't need 100Mbps).

TTYL

--=20
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