[Kok-Yong Tan <ktan@xxxxxxxxxxxxxxxxxxx>]

Since the OP didn't mention anything about whether the switch the 
printer is connected to is manageable or not, I assumed that it's an 
unmanaged dumb switch with no duplex settings possible (i.e., these are 
usually set to autonegotiate). Since OP's printer is set to full duplex 
and has autonegotiation disabled and is directly connected to an 
autonegotiating switch, that means the port on the switch which OP's 
printer is connected to will failover into half-duplex. So there's a 
duplex mismatch right there, no?

On 7/12/12 18:05, jim@xxxxxxxxxxxxxxxxx wrote:
> That is not correct. It would be a good practice to use the same
> autonegotiation settings throughout your network, but the printer and the
> desktop PC do NOT have to match. Autonegotiation takes place only between
> two directly connected NICs. The NIC in the desktop PC must have the same
> autonegotiation settings as the port that it is connected to on switch C.
> The NIC in the printer must have the same autonegotiation settings as the
> port that it is connected to on switch B. The desktop PC and the printer do
> not autonegotiate with each other. They do not have a direct physical
> connection to each other.
>
> So the printer is set for full duplex with autonegotiation disabled. If the
> switch port that it is connected to is also set to full duplex with
> autonegotiation disabled, then both sides match and the link will be full
> duplex.
>
> The desktop PC has autonegotiation enabled. If the switch port that it is
> connected to also has autonegotition enabled, then the two devices SHOULD
> negotiate a full duplex connection.
>
> Flako, a duplex mismatch could still be a problem, but you need to check
> the desktop PC against the directly connected switch port, not against the
> printer; and check the printer against its directly connected switch port,
> not against the desktop PC.
>
> In any case, you want to make sure that both links are full duplex; that
> is, that all four NICs are set to and actually operating at full duplex. If
> one link is half duplex, even if both ends match, it will still have less
> throughput than the other link and can result in dropped packets under high
> load.
>
> And again, you've got a capacity mismatch between the two switches (100mbps
> vs 1 Gbps). If these switches maintains per-port counters, you might want
> to check each port for dropped frames.
>
> Original Message:
> -----------------
> From: Kok-Yong Tan ktan@xxxxxxxxxxxxxxxxxxx
> Date: Thu, 12 Jul 2012 17:15:57 -0400
> To: wireshark-users@xxxxxxxxxxxxx
> Subject: Re: [Wireshark-users] 8-10% packet error/loss is
> normalwired	network?
>
>
> Are your statements above accurate (printer has autonegotiation
> *DISABLED* and desktop has autonegotiation *ENABLED*)?  Both devices
> *MUST* match, even if one has autonegotiation enabled.  i.e., If the
> desktop has autonegotiation enabled, then the printer *MUST ALSO* have
> autonegotiation enabled.  Otherwise autonegotiation will fail and the
> device with autonegotiation enabled will drop down to half duplex.   See
> this:
>
> <http://en.wikipedia.org/wiki/Duplex_mismatch#Duplex_mismatch_due_to_autoneg
> otiation>
>
> Hansang Bae mentioned this in a session at a prior Sharkfest during one
> of his very illuminating "Deep Dive" packet analysis sessions.
>
> Reality Artisans, Inc.             #   Network Wrangling and Delousing
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> (212) 369-4876 (Voice)             #   My PGP public key can be found
> at<https://keyserver.pgp.com>
>
>
>
>
>
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