[c-nsp] Ethernet autonegotiation issue between Cat3560 and Cat2960

[Juuso Lehtinen]

I replaced the cable today with similar straight-thru cable. Links seem to
autonegotiate now to a-1000. Tried plugging and unplugging cable several
times, and every time autonegotiation went fine.

Still a bit confused about the root cause of this problem. I was able to fix
the autonegotiation on the old cable yesterday by executing 'media-type
rj45' on suspended port. After that, port seemed to perform autonegotion
again and suspended state was raised. Didn't see the problem resurface again
even after reverting back to  'media-type auto-select'.

-Juuso


On Sun, Nov 22, 2009 at 6:52 PM, Juuso Lehtinen <juuso.lehtinen at gmail.com>wrote:

> Thanks to all for answers,
>
> Cables straight-thru, and identical cables are used for the working and
> suspended trunks.
>
> I will try replacing the cable with a new one tomorrow. If that does not
> help, will try disabling autonegotiation.
>
>
>
> On Sun, Nov 22, 2009 at 6:05 PM, Nick Hilliard <nick at inex.ie> wrote:
>
>> On 22/11/2009 12:46, Juuso Lehtinen wrote:
>>
>>> Any ideas what might be causing this. I wonder if I'm running into some
>>> kind
>>> of minimum cable length problem. Switches are sitting adjacent to each
>>> other
>>> in a rack and connected with very short cables (0.5m ~ 2 ft).
>>>
>>
>> Are you sure you're using the correct cable type?  Either you should use a
>> regular 568-B straight-thru cable, or else you should use a full GE
>> crossover cable, which is wired like this:
>>
>> 1.      white/orange    ->      white/green
>> 2.      orange/white    ->      green/white
>> 3.      white/green     ->      white/orange
>> 4.      blue/white      ->      brown/white
>> 5.      white/blue      ->      white/brown
>> 6.      green/white     ->      orange/white
>> 7.      white/brown     ->      white/blue
>> 8.      brown/white     ->      blue/white
>>
>> Note that for a 100M cross-over, you only cross orange with green, but for
>> GE, you need to cross blue with brown too.
>>
>> Even if you're sure about the cabling, it's no harm to test it out with a
>> decent cable tester.  Maybe there's something strange going on with the UTP
>> termination plugs?
>>
>> Cable length is only a problem where you use co-ax, as the co-axial cable
>> medium can encourage all sorts of strange effects (signal reflection, timing
>> problems, etc).
>>
>> Nick
>>
>>
>