Ethereal-users: RE: [Ethereal-users] How to identify a runt and its source

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From: David Edward Shapiro <David.Edward.Shapiro@xxxxxxxxxxx>
Date: Wed, 21 Feb 2001 10:06:43 -0500
Well,  I am running 100fdx at the switch and on the server.  This was done
as part of the trouble shooting though.  It was previously 100hdx on both.
The get enough inbound packet errors on the server to show there is a
problem.  I see the runt report on the switch, and the number is large.  I
need to know how to identify runts and their source with ethereal or
tethereal.  Any ideas?

-----Original Message-----
From: McNutt, Justin M. [mailto:McNuttJ@xxxxxxxxxxxx]
Sent: Tuesday, February 20, 2001 5:53 PM
To: ''ethereal-users@xxxxxxxxxxxx' '
Subject: RE: [Ethereal-users] How to identify a runt and its source


You will never see collisions if you are set to full duplex, and it is
probable that *your* machine is the source of the runts.

If you have forced your card to 100FDX, then it won't participate in
autonegotiation.  Since it doesn't participate, you have to force the switch
to 100FDX as well.

If you don't, the switch will assume that it is attached to a generic
Ethernet, which could mean a hub, which means 100Mb HALF duplex.

So the switch is trying to transmit, and you blast out a frame (since you
think you're running FDX), the switch stops transmitting because it sees a
collision, and you interpret the aborted frame as a runt.

Always, always, always run half duplex on station- or server-to-switch
ports.  Full duplex causes far more problems than it solves.  If you need
more bandwidth, get a dual-port NIC, or a faster (1000Mb) NIC.  Full duplex
will ruin your life.

No flow control, failed autoneg, poorly written drivers...

--J

P.S.  Collisions are a side effect of using half duplex.  Collisions are NOT
a problem.  Only Late collisions are a problem (and Excessive Collisions,
which show up as "dropped" in 'ifconfig'.  Normal collisions are merely the
Normal Way that Ethernet negotiates control of the wire.

-----Original Message-----
From: David Edward Shapiro
To: 'ethereal-users@xxxxxxxxxxxx'
Sent: 2/20/01 3:17 PM
Subject: [Ethereal-users] How to identify a runt and its source

How do you identify runt packets and their source?  My two interfaces
that
are connected to switch ports at 100 full with no collisions are getting
high runt counts on the switch and tools like se-toolkit from SUN tell
me I
have problems with either cable, cards, or other.  I would like to know
how
to idenify the runt packets and their source, but I am unsure how to do
that
with ethereal.  Can it be done?  

David


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