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Redux - RE: Problems connectivity GE on Foundry BigIron to Cisco2950T

  • From: Sam Stickland
  • Date: Thu Jan 19 08:56:53 2006


I've had a lot of emails asking me how I was getting on with this, so I figured I'd do a quick redux of the issues for the archives.

One of the main problem actually turned out to be a damaged strand in the CAT5e underfloor cabling, which meant that the connection would work at 10/100, but not at 1000 (GE) because of the use of extra pairs on GE. So leaving comments about castrating the cabling the engineer who assured me it had tested fine aside ;) the other problems we encountered were:

Foundry's GE auto-negotiation seems very tempermental.

Another engineer here just told there's a connection (on SX/MM) between a Foundry BigIron and clients Dell switch in the network where both ends only get a link light when the Foundry is configured to neg-full-auto (Autonegotiation first, if failed try non-autonegotiation). auto-gig (Autonegotiation) and neg-off (Non-autonegotiation) don't work! Only neg-full-auto on which the connection is fine and stable.

We ditched the copper GBIC and used a 1000Base-SX to 1000Base-TX convertor. The foundry won't form a real link (from a fixed SX/SC blade) with the 1000Base-SX convertor until "gig-default auto-gig" is entered. With the default settings both ends get a link light but the Foundry never sees any mac-addresses.

The cisco 2950T does support auto MDI/MDI-X on the gigabit copper ports dispite this not being mentioned in the any switch specification I could find. I never did have any luck with a GE cross-over cable (even not using the damaged underfloor cabling).

Dispite never being able to get a link-light between the Foundry Copper GBIC and the cisco 2950T, I've since found another point in our network, using exactly the same model GBIC in this configuration, that's working fine. The GBIC has since been placed back into a cisco 6500 where it's working fine (hooked at to a 10/100/1000 port on another cisco 6500).

So, multi-vendor Copper GE - not always as easy as it sounds!


On Mon, 16 Jan 2006 wrote:

Hopefully the cisco copper GBIC supports Auto-MDI though, so a straight cable should be good.


On Sun, 15 Jan 2006, David Prall wrote:

Hash: SHA256

GigE 1000Base-T requires all 4 pairs of wire. Auto-MDI is not supported on the 2950 series, so it won't handle this automagically. I would test with speed set to 100 if the foundry can support 10/100/1000 with the Copper GBIC. Put the two next to each other and test with 1000Base-T crossover cable, removing all the extra stuff if that doesn't work.

1000Base-T requires that pairs 1 and 4 are also crossed along with 2 and 3.


- --
David C Prall

-----Original Message-----
From: [] On
Behalf Of Mark Smith
Sent: Sunday, January 15, 2006 5:44 PM
To: Randy Bush
Subject: Re: Problems connectivity GE on Foundry BigIron to
Cisco 2950T

Hi Randy,

On Sun, 15 Jan 2006 11:10:04 -1000
Randy Bush <> wrote:

You are using a crossover cable right?
I'm having a right mare trying to get a Foundry BigIron to
connect up to a cisco 2950T, via Gigabit copper.
i was under the impression that gige spec handled crossover

According to "Ethernet, The Definitive Guide", that feature is an
optional part of the spec.

One thing I've heard people encounter is that if they use a cross-over
cable, which probably really implies a 100BASE-TX cross-over, then the
ports only go to 100Mbps. A Gig-E rated straight through, in
with the automatic crossover feature, was necessary to get to GigE.



        "Sheep are slow and tasty, and therefore must remain
                                   - Bruce Schneier, "Beyond Fear"

Version: PGP Desktop 9.0.3 (Build 2932)


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