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duplex negotiation

 
 
flamer die.spam@hotmail.com
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      03-19-2007
I have a link between a baystack switch and a cisco 1841 router, I
have the
same setup and same configuration at 70 other sites and have not seen
this problem before.. when each device is manually set to 100/full the
link goes down and I get no lights on either end, when one end is set
to auto/auto and the other manually to 100/full the link comes up as
100/full for anywhere between 10secs and several hours then drops back
to half duplex. when both ends were auto auto they came up 100/half, I
set
the duplex on the switch only to full then the link was running 100/
full, I tried manually setting the speed/duplex when the link was
running correctly but that killed the link again and I couldn't get it
running back at 100/full again.

I have tried different switchports and it has the same problem, is it
possible for a device to mis-report what duplex its running at? we are
going to replace the cabling to ensure its not faulty but because it
was able to run at full duplex it rules out a dodgy pair in the cable.

at all the other sites we have 100/full statically set on the
interfaces at each end.

Flamer.

 
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Christoph Gartmann
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      03-20-2007
In article <(E-Mail Removed) .com>, "flamer http://www.velocityreviews.com/forums/(E-Mail Removed)" <(E-Mail Removed)> writes:
[...]
>I have tried different switchports and it has the same problem, is it
>possible for a device to mis-report what duplex its running at?


Yes, it is although this shouldn't be.

>we are going to replace the cabling to ensure its not faulty but because it
>was able to run at full duplex it rules out a dodgy pair in the cable.


Not only the cable but as well the plugs could be the problem.

>at all the other sites we have 100/full statically set on the
>interfaces at each end.


This should work. But I remember cases where devices from different brands or
even different models from the same brand couldn't cope with each other.
In addition, do your switches have the lastest software updates?

Regards,
Christoph Gartmann

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Postfach 1169 Internet: gartmann@immunbio dot mpg dot de
D-79011 Freiburg, Germany
http://www.immunbio.mpg.de/home/menue.html
 
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Jim Allen
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      03-20-2007
On 19 Mar 2007 16:04:19 -0700, "flamer (E-Mail Removed)"
<(E-Mail Removed)> wrote:

>I have a link between a baystack switch and a cisco 1841 router, I
>have the
>same setup and same configuration at 70 other sites and have not seen
>this problem before.. when each device is manually set to 100/full the
>link goes down and I get no lights on either end, when one end is set
>to auto/auto and the other manually to 100/full the link comes up as
>100/full for anywhere between 10secs and several hours then drops back
>to half duplex. when both ends were auto auto they came up 100/half, I
>set
>the duplex on the switch only to full then the link was running 100/
>full, I tried manually setting the speed/duplex when the link was
>running correctly but that killed the link again and I couldn't get it
>running back at 100/full again.
>
>I have tried different switchports and it has the same problem, is it
>possible for a device to mis-report what duplex its running at? we are
>going to replace the cabling to ensure its not faulty but because it
>was able to run at full duplex it rules out a dodgy pair in the cable.
>
>at all the other sites we have 100/full statically set on the
>interfaces at each end.
>
>Flamer.


If one side of a connection is set to auto-negotiate and the other
side to full duplex the auto-negotiate side will default to half
duplex. Cisco recommends both sides of the link be set to
auto-negotiation -

Configuring and Troubleshooting Ethernet 10/100/1000Mb Half/Full
Duplex Auto-Negotiation

http://www.cisco.com/en/US/customer/...80094781.shtml

If you manually set both sides to 100/full you need to watch the
errors. If the wiring is inadequate your error rate can get quite
high.

- Jim
 
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flamer die.spam@hotmail.com
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      03-20-2007
On Mar 20, 9:38 pm, Jim Allen <(E-Mail Removed)> wrote:
> On 19 Mar 2007 16:04:19 -0700, "flamer (E-Mail Removed)"
>
>
>
> <(E-Mail Removed)> wrote:
> >I have a link between a baystack switch and a cisco 1841 router, I
> >have the
> >same setup and same configuration at 70 other sites and have not seen
> >this problem before.. when each device is manually set to 100/full the
> >link goes down and I get no lights on either end, when one end is set
> >to auto/auto and the other manually to 100/full the link comes up as
> >100/full for anywhere between 10secs and several hours then drops back
> >to half duplex. when both ends were auto auto they came up 100/half, I
> >set
> >the duplex on the switch only to full then the link was running 100/
> >full, I tried manually setting the speed/duplex when the link was
> >running correctly but that killed the link again and I couldn't get it
> >running back at 100/full again.

>
> >I have tried different switchports and it has the same problem, is it
> >possible for a device to mis-report what duplex its running at? we are
> >going to replace the cabling to ensure its not faulty but because it
> >was able to run at full duplex it rules out a dodgy pair in the cable.

>
> >at all the other sites we have 100/full statically set on the
> >interfaces at each end.

>
> >Flamer.

>
> If one side of a connection is set to auto-negotiate and the other
> side to full duplex the auto-negotiate side will default to half
> duplex. Cisco recommends both sides of the link be set to
> auto-negotiation -
>
> Configuring and Troubleshooting Ethernet 10/100/1000Mb Half/Full
> Duplex Auto-Negotiation
>
> http://www.cisco.com/en/US/customer/...chnologies_tec...
>
> If you manually set both sides to 100/full you need to watch the
> errors. If the wiring is inadequate your error rate can get quite
> high.
>
> - Jim


Thanks for the advice both of you, I am thinking now that perhaps the
devices never really were running at full-duplex and the cable may
need replacing, although on the cisco it was reporting full duplex and
no errors for a while now it half duplex it has many errors and resets
on the interface. I know there have always been auto neg issues with
cisco in the past but all the routers and switches are running the
same ios versions and have the same config and everything so its just
one site that isn't working correctly. should i try set the port
duplex/speed without the cable plugged in maybe?

Flamer.

 
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none
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      03-22-2007
On Tue, 20 Mar 2007 09:38:12 +0000, Jim Allen wrote:

> Cisco recommends both sides of the link be set to auto-negotiation -


The article on the Cisco site you quoted says different...

"Both sides of a link should have auto-negotiation on, or both sides
should have it off. Cisco recommends to leave auto-negotiation on for
those devices compliant with 802.3u."
 
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Bod43@hotmail.co.uk
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      03-22-2007
On 22 Mar, 00:24, none <(E-Mail Removed)> wrote:
> On Tue, 20 Mar 2007 09:38:12 +0000, Jim Allen wrote:
> > Cisco recommends both sides of the link be set to auto-negotiation -

>
> The article on the Cisco site you quoted says different...
>
> "Both sides of a link should have auto-negotiation on, or both sides
> should have it off. Cisco recommends to leave auto-negotiation on for
> those devices compliant with 802.3u."


Autonegotiation is almost always superior to any manual
fiddling - as a general statement.

This issue feels like a bad cable. With FD there are greater
demands on the cable since both ends may be transmitting
at the same time. This means that the receiver has to be
able to cope with its own transmitter blasting out with
orders of magnitude more power than the expected
received signal. To make this work you need a
proper cable.

Bear this in mind - autonegotion is good.

More networking problems have been caused by
misguided manual intervention in this area
than have ever been fixed by it.

Read the current Cisco advice and believe it.
If it's not working as advertised something is broken.

Until a few years ago I NEVER trusted the duplex
setting reported. Trust ONLY the error counters
on networking equipment that you trust. I you
have old kit then suspect the settings reported.


 
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flamer die.spam@hotmail.com
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      03-22-2007
On Mar 22, 1:14 pm, (E-Mail Removed) wrote:
> On 22 Mar, 00:24, none <(E-Mail Removed)> wrote:
>
> > On Tue, 20 Mar 2007 09:38:12 +0000, Jim Allen wrote:
> > > Cisco recommends both sides of the link be set to auto-negotiation -

>
> > The article on the Cisco site you quoted says different...

>
> > "Both sides of a link should have auto-negotiation on, or both sides
> > should have it off. Cisco recommends to leave auto-negotiation on for
> > those devices compliant with 802.3u."

>
> Autonegotiation is almost always superior to any manual
> fiddling - as a general statement.
>
> This issue feels like a bad cable. With FD there are greater
> demands on the cable since both ends may be transmitting
> at the same time. This means that the receiver has to be
> able to cope with its own transmitter blasting out with
> orders of magnitude more power than the expected
> received signal. To make this work you need a
> proper cable.
>
> Bear this in mind - autonegotion is good.
>
> More networking problems have been caused by
> misguided manual intervention in this area
> than have ever been fixed by it.
>
> Read the current Cisco advice and believe it.
> If it's not working as advertised something is broken.
>
> Until a few years ago I NEVER trusted the duplex
> setting reported. Trust ONLY the error counters
> on networking equipment that you trust. I you
> have old kit then suspect the settings reported.


the work we did yesterday seemed to go well, we had to use a straight
through cable (cat5e which is more than adequate for 100mb/fd) and
strapped both sides manually o 100/full the link stayed stable and
had no errors or collisions reported.. I kept a watch on the counters
for 25mins and stayed running fine I have to check again today to see
if its still running fd with no errors.. I can't see why it wouldn't..
cross-over cable still immediately killed the link..

Flamer.

 
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