News Group Posts

nic kills network

This post describes a very confused nic.

Slowing down is actually harder to diagnose than something like duplicate ip's or duplicate MAC addresses. This long thread first suspected lightning damage but finally got to the root cause.

From: Jeff Liebermann <jeffl@comix.santa-cruz.ca.us>
Newsgroups: comp.unix.sco.misc
Subject: Re: suddenly slow network- more info, need more help
Date: Wed, 02 Aug 2000 22:42:29 -0700
Message-ID: <vl0ios0hk010a8q7ng6045cl1rvl7smved@4ax.com> 

On Wed, 02 Aug 2000 09:30:48 -0400, - bill - <bill@TechServsys.com>
wrote:

I guess you've eliminated aliens and teenagers as possible culprits.

>(BTW: with the linksys I can not ping the server from a win98
>pc on the network)  I replaced the Linksys with the 3com and, although
>slow the network works.  So I guess the next step is to replace the
>server NIC 3com 3c905b as it seems to be spewing garbage.

Yep.  Actually, most hubs will NOT show traffic from an insane NIC.  Nor
will the traffic monitors that expect valid data instead of garbage.

>Anyone have any thoughts on this diagnosis ?

Yeah.  What's happening is the the NIC receiver is not decoding MFM data
properly.  It thinks it's getting "malformed" packets and is firing off
the "trashing" mechanism, by which ethernet intentionally trashes mangled
packets.  The dual speed hub (I hate those) will not propogate collisions
and garbage across the internal bridge between the 100 and 10 side of the
hub.  Therefore, your 10baseT devices probably work just fine, while your
100baseT machines may be having a difficult time.

>Part II:  I have never replaced a NIC in a 505 system yet.  Can I use
>the gui and just delete the NIC (and, I presume the associated protocol
>and NFS runtime) and then swap cards and reinstall the nic/protocol/nfs
>runtime) or is there an easier way ?

If it's another 3c905[a|b|c], then just plug it in and it's done.  No
configuration.  If it's a different flavour, you should probably backup
the major config files, remove the driver, shove in the new card, install
the driver, and you might luck out that the stack recognizes "net0" as
being the same as before and without reconfiguration.  I did this once
and vaguely recall that all the configuration files were retained as long
as the driver was called net0.  However, I was running in fire-drill
mode, and didn't have time to be sure.


-- 
Jeff Liebermann   jeffl@comix.santa-cruz.ca.us
150 Felker St #D  Santa Cruz CA  95060
831-421-6491 pager   831-429-1240 fax
http://www.cruzio.com/~jeffl/sco/   SCO stuff

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