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Ethernet autonegotiation issue between Cat3560 and Cat2960

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juuso.lehtinen at gmail

Nov 22, 2009, 4:46 AM

Post #1 of 10 (871 views)
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Ethernet autonegotiation issue between Cat3560 and Cat2960

Hi,

I have Catalyst 3560 and 2960 switches connected by a two member
Etherchannel trunk using built in copper GE interfaces. For some reason
Ethernet autonegotiation ends up assigning unmatching speeds for one link
(10M in one switch, 100M in other) and the interfaces end up in suspended
state.

MGMT-14#show int status | inc 35|36
Gi0/35 connected trunk a-full a-1000
10/100/1000BaseTX
Gi0/36 suspended trunk a-full a-100
10/100/1000BaseTX

MGMT-13#show int status | inc 23|24
Gi0/23 connected trunk a-full a-1000
10/100/1000BaseTX
Gi0/24 suspended trunk a-full a-10
10/100/1000BaseTX

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).

-Juuso Lehtinen
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sthaug at nethelp

Nov 22, 2009, 6:26 AM

Post #2 of 10 (841 views)
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Re: Ethernet autonegotiation issue between Cat3560 and Cat2960 [In reply to]

> I have Catalyst 3560 and 2960 switches connected by a two member
> Etherchannel trunk using built in copper GE interfaces. For some reason
> Ethernet autonegotiation ends up assigning unmatching speeds for one link
> (10M in one switch, 100M in other) and the interfaces end up in suspended
> state.
>
> MGMT-14#show int status | inc 35|36
> Gi0/35 connected trunk a-full a-1000
> 10/100/1000BaseTX
> Gi0/36 suspended trunk a-full a-100
> 10/100/1000BaseTX
>
> MGMT-13#show int status | inc 23|24
> Gi0/23 connected trunk a-full a-1000
> 10/100/1000BaseTX
> Gi0/24 suspended trunk a-full a-10
> 10/100/1000BaseTX
>
> 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).

There is *no* minimum cable length requirement for 1000baseT.

I would start by replacing the cable connecting the two suspended ports.

Steinar Haug, Nethelp consulting, sthaug [at] nethelp
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daniele at orlandi

Nov 22, 2009, 7:37 AM

Post #3 of 10 (819 views)
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Re: Ethernet autonegotiation issue between Cat3560 and Cat2960 [In reply to]

On Sunday 22 November 2009 13:46:34 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).

You aren't using a cross cable, are you?

Bye,

--
Daniele "Vihai" Orlandi
Bieco Illuminista #184213
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nick at inex

Nov 22, 2009, 8:05 AM

Post #4 of 10 (827 views)
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Re: Ethernet autonegotiation issue between Cat3560 and Cat2960 [In reply to]

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

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juuso.lehtinen at gmail

Nov 22, 2009, 8:52 AM

Post #5 of 10 (823 views)
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Re: Ethernet autonegotiation issue between Cat3560 and Cat2960 [In reply to]

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> 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
>
>
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nick at inex

Nov 22, 2009, 9:28 AM

Post #6 of 10 (820 views)
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Re: Ethernet autonegotiation issue between Cat3560 and Cat2960 [In reply to]

On 22/11/2009 16:52, Juuso Lehtinen wrote:
> 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.

If you disable autonegotiation, you will need to use a GE cross-over cable,
as disabling speed negotiation on a cisco switch usually (but not always)
disables mdi/mdix negotiation.

Nick
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daniele at orlandi

Nov 22, 2009, 2:17 PM

Post #7 of 10 (811 views)
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Re: Ethernet autonegotiation issue between Cat3560 and Cat2960 [In reply to]

On Sunday 22 November 2009 18:28:07 Nick Hilliard wrote:
>
> If you disable autonegotiation, you will need to use a GE cross-over cable,

I don't think so, because with GE there are no RX and TX pairs to be crossed
as all four pairs are both for transmission and reception.

--
Daniele "Vihai" Orlandi
Bieco Illuminista #184213
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pavel.skovajsa at gmail

Nov 23, 2009, 2:46 AM

Post #8 of 10 (800 views)
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Re: Ethernet autonegotiation issue between Cat3560 and Cat2960 [In reply to]

Hi,

I would approach this the indirect way - try shuffling the switches
around to see which combinations work & which not. This is the
"universal engineer" approach :)

-pavel skovajsa

On Sun, Nov 22, 2009 at 11:17 PM, Daniele Orlandi <daniele [at] orlandi> wrote:
> On Sunday 22 November 2009 18:28:07 Nick Hilliard wrote:
>>
>> If you disable autonegotiation, you will need to use a GE cross-over cable,
>
> I don't think so, because with GE there are no RX and TX pairs to be crossed
> as all four pairs are both for transmission and reception.
>
> --
> �Daniele "Vihai" Orlandi
> �Bieco Illuminista #184213
> _______________________________________________
> cisco-nsp mailing list �cisco-nsp [at] puck
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>
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juuso.lehtinen at gmail

Nov 23, 2009, 4:16 AM

Post #9 of 10 (794 views)
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Re: Ethernet autonegotiation issue between Cat3560 and Cat2960 [In reply to]

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>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> 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
>>
>>
>
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rsm at fast-serv

Nov 23, 2009, 6:39 AM

Post #10 of 10 (797 views)
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Re: Ethernet autonegotiation issue between Cat3560 and Cat2960 [In reply to]

Bad cable... It happens.

--
Randy

---------- Original Message -----------
From: Juuso Lehtinen <juuso.lehtinen [at] gmail>
To: cisco-nsp [at] puck
Sent: Mon, 23 Nov 2009 14:16:47 +0200
Subject: Re: [c-nsp] Ethernet autonegotiation issue between Cat3560 and Cat2960

> 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.

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