Brian Hechinger wrote:

> since i just picked up a bunch of older AUI only (or AUI+10Base-2) DEC
> boxes, i figured that instead of buying a bazillion transceivers i should
> grab these two cheap boxes off of ebay:
>
> Cabletron Systems MT-800 Multiport Transceiver Unit (MAU)
>
> one "uplink" AUI port and 8 "regular" ports.  got two of the bastards.

I don't think that AUI port is going to help you in connecting the "DEC boxes"
- it's for the node end of the AUI connection (i.e., the same end as the DEC
boxes), not the "tap" end.

> the question are this:
>
> what is SQE?
> should i enable it?

Perhaps the following will shed some light:

From: oberman@ptavv.llnl.gov
Newsgroups: comp.dcom.lans.ethernet
Subject: Re: SQE, Once more

In article <1992Jul31.124357.10781@relay.nswc.navy.mil>,
tdrake@relay.nswc.navy.mil (Tim Drake - E41) writes:
>
>    I've read all the postings on SQE I've seen in the last two
> weeks (many). I'm still unclear on a few points. SQE should
> help me find problems in faulty MAU's, but how?? Say I'm working
> on a Unix system, what command will report the error's I shoud see
> if I have SQE turned on and the MAU is faulty. In short how can
> SQE help me find problems.

You've just hit one of my big gripes with vendors. Many, but not all U*ix OSes
simply ignore the SQE error. In this environment there is little you can do
with the fact that SQE is enabled except to complain loudly to the vendor.

For those systems that do count SQE errors, something like netstat should
return the counts. SNMP is a better way to get this information.

>   My other confusion is if it looks like a collision to my MAU
> (the "CP collision packet" LED lights up) how does the system
> tell the difference between the "test" and an actual collision?

It's all a matter of timing. The SQE signal is generated immediately after a
packet is transmitted. During this interval the network is not (or should not)
be carrying any traffic. Since the SQE check is sent by the MAU itself, it
expects it and so does the controller.

>   I must admit that we turn SQE off religiosly because of problems
> we had with it being enabled and connected to repeater equipment.

Amazing to me how many people don't read the instructions, hook up a MAU with
SQE enabled to a repeater, have it fail, and declare SQE a BAD THING to be
turned off all the time. I know of several sites that operate this way and I
think they are all crazy (or lazy).

If a driver counts SQE errors, as many do, turning off SQE has deprived you of
a significant tool for discovering network problems. If a driver does not count

SQE errors, the vendor has deprived you the tool and you should complain
LOUDLY!

R. Kevin Oberman                        Lawrence Livermore National Laboratory
Internet: koberman@llnl.gov             (510) 422-6955


--

Philip J. Tait.....Honeywell, Phoenix, Az.....pjt@phxase.allied.com