[c-nsp] Network Analyser with n-way support

[Ted Mittelstaedt]

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net]On Behalf Of Thomas Kernen
> Sent: Thursday, January 13, 2005 5:13 AM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] Network Analyser with n-way support
>
>
>
> Currently debugging an issue with autonegociation (n-way) between 2
> network devices for which it appears that neither vendor can solve the
> issue directly. We are now trying to locate an analyser that
> will allow
> us to sniff the n-way negociation from both devices but without the
> ports on the analyser doing their own negociation with the end
> devices,
> so basically I'm looking for a "pass through" analyser.
>

I don't think anything like that exists in the commercial realm because
such problems are usually solved by inserting a switch in between
the devices - thus no commercial viability.  Why don't you do that and
see what happens?

I've got an Ethernet hub at the office that most Cisco routers
work fine in, but plug in a Cisco 804 and it starts shrieking
about "late collisions"  Plug in a Westell DSL modem and if the
Westell has early-revision firmware it won't work at all, flash
update the Westell and it starts working.

I have this hub on the test bench as it occasionally comes
in handy to have an oddball ethernet device around.

I also have the same problem with a router/PC running an Intel
Etherexpress Pro 100 plugged into a horribly expensive switch
at a colo site.  The colo vendor normally hard-codes the autonegotiation
on this switch to 100/Full, because they say that autonegotiation
is unreliable.  My gear loses about 2% of the packets when they
do this no matter how I have my side set.  When they set to
autonegotiation on their side (after lecturing me on how doing
this is a Bad Thing) and I set to autonegotiation, the packet loss
goes away.  However the downside is about 1 in 10 reboots, their
port goes to a funny state and stops talking.  I can kick it by
a quick set of the port on my side to 10base/half, then back to
auto.

And I personally made them let me go through their cable plant
and cut off and recrimp and repunch every jack and plug in the
connection between my router and their switch (and I won't even
go into the mistakes and messes I found while doing that)

At one remote site we had a customer with a Cisco 1605 plugged into a
fiber module that is hard-coded 10/half.  The error log in the router was
stuffed with late collision errors.  I went to Goodwill, bought an old
unicom 4 port 10Base T hub for $4.99, found an A/C adapter in a bin
there for a buck rated the right power and soldered on the correct
plug to the end, inserted the hub in between the fiber module and the
router - voila, problem vanished.

> Unfortunally I'm unable to locate such a device that does provide not
> only the layer 2/3/+ but also the "pass through" feature for
> the ports.
> Suggestions or workarounds are welcomed.
>

You are way overengineering this.  Accept the fact that Ethernet
isn't a particularly good kind of interconnect to use in between
network devices and the reason it's used is because it's cheap,
buy a switch, and move on.

I would also venture a guess that your a young guy.  Old timers
that dealt with Ethernet years ago had these problems all of the
time and have many stories to tell.  You haven't lived until you've
debugged a thinnet network.

Ted