UPDATE: 3Com Linkswitch 1000 & Telnet

From: Lyle Scully (lyle@azlink.com)
Date: Thu Aug 08 1996 - 18:32:16 CDT

First the original message:

We are using a Linkswitch 1000 from 3Com here on our network. During normal
operation there is a yellow light that flashes to signify data going in and
out. But every 25-30 seconds all active lights (meaning all ports that are
currently in use) will flash on and stay solid for about 2 seconds.
Everytime it does it we experience a pause in all traffic (wether we are
talking ftp or Telnet or http it doesn't matter). Why is it doing this? Is
there a way to fix it so that it is a lot smoother? It is causing all
Telnet sessions through a modem to pause for a significant amount a time.
As far as local workstations it is not so bad but it is there and can be
very annoying. FTP doesn't seem to be effected as badly.

Summary of replies:

The general consensus was that it is a broadcast storm. I went into the
stats and checked all ports and found that the "Broadcasts Received" for
one machine was up in the 5million range while all other ports were in the
0-50 range (that is 50 received not 50million). While on the phone with a
3Com rep that was trying to help me out with this, he said the same thing.

Based on another reply I tried running snoop and watching the traffic.
Problem is I don't really know what I am looking for. While running snoop
(ran it this way... snoop -P -t a -d le0) and the pause came in it seemed
that it was an RCP transmission. But on another one the output showed
regular TCP transmissions. So either I am looking for the wrong things

Was also told to check the cabling and the network card in the machine that
is doing this. Will put a new cable on it tonight and switch the 10BaseT
that is in it right now with my new Fast Ethernet card. I have two nearly
identical machines and one is doing it and the other is not. Here is the
hardware involved (on the local network):

2 SunSparc 20's (one SuperSparc 85 and one HyperSparc 100)
1 3Com LinkSwitch 1000
1 Livingston Portmaster
2 Windows 95 workstations
1 Macintosh workstation

The port that is having all the "Broadcast Received" problems is my Web
Server (SuperSparc 85). It is running Solaris 2.5.1. But it was doing this
when it was Solaris 2.4 also. The other server is still running Solaris

One thing that I noticed this morning was that there was approximately "50"
in.rarpd processes running. Could that be having an effect? If so is it
"safe" to prune back these processes? The only other thing I can think of
is the Apache and/or Netscape web servers that are currently running. Are
there processes that I should be looking for on the server side that might
be broadcasting? Is it possible that it is one of those 3 workstations (or
perhaps our dedicated client line that is a unix system on the other end

Sorry for the length of this message. I don't really know how to proceed
from here.

Thanks to these people for the really quick replies:

jonesmd@unifiedtech.com (Mike Jones)
daves@adnc.com (David Schiffrin)
Paul Kanz <paul@icx.com>
Michael Baumann <baumann@proton.llumc.edu>
bismark@alta.jpl.nasa.gov (Bismark Espinoza)
George Spafford <gspaff@execpc.com>
Tony Jago <tony@fit.qut.edu.au>

Thanks again,


Status: RO

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