We are seeing very strange interaction between Alphaserver 4100s
and 3Com SuperStack II switch 3300s, I'm hoping someone has
some clues.
We recently set all our alphas (Alphaserver 4100s and GS140s, Tru64 v4.0F)
to 100Mbit full-duplex at the console level, via commands of the form:
> set ewa0_mode fastfd
The alphas indicate they are indeed 100Mbit/full during boots.
The NICs in these systems are mostly DE500s, with one particular
system having 2xDE504 quad cards. The NICs are directly connected
to 3Com Superstack II switch 3300s.
When we set the alphas to 100Mbit full-duplex we at the same time
set the associated ports on the switches to 100Mbit full-duplex
*NO* autonegotiate.
Subsequent testing by doing scps of 1GB+ files between hosts indicates
that all but one interface worked, though the speed was nowhere near
what I would expect - best speed is about 2.3MB/sec. The one interface
that was not working hung after 40MB or so, which in past tests was
indicative of a mismatch in duplex settings between the NIC and
the switch.
We did some debugging, and found the following:
Switch ports set to 100Mbit full-duplex no autonegotiate
work flawlessly with alphas set at console mode to 100Mbit
full-duplex.
Switch ports set to autonegotiate come up as 100Mbit
half-duplex. They also work flawlessly with these same
alphas set at console mode to 100Mbit full-duplex.
Testing in all cases involves scp copies of 1GB+ files, and speeds
in all cases are in range of 2.3MB/sec.
It is not possible that the switch settings can both be right, however,
is it? It should not be possible to consistently move files from 100Mbit
full-duplex nic and 100Mbit half-duplex switch, and also from 100Mbit
full-duplex nic and 100Mbit full-duplex switch! It seems to
me that one of the following must be true:
- Alpha NICs are really only operating at 100Mbit half-duplex
and switch ports are indeed switching between half-duplex
and full-duplex.
- Alpha NICs are truly operating at 100Mbit full-duplex
and switch ports are always running at 100Mbit full-duplex,
even though auto-negotiate says otherwise.
The documentation on the 3Com switches indicates they do indeed
support 10/100 half/full.
Anyone ever seen anything like this? We are certainly not getting
speeds that would indicate 100Mbit full, but we have not yet specifically
tested two hosts that we are sure are on the same switch, so the only
limiting factor would be the backplane - we need to do this test.
TIA...
Judith Reed
jreed_at_appliedtheory.com
Received on Fri Mar 30 2001 - 19:28:02 NZST