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pfisterfarm 12-06-2011 04:19 PM

Need help with port duplex settings
 
We have a newly installed 4506e switch, which is uplinked to our
upstream provider's ME3400 switch (CSME). The provider's switch is
hard coded to 100/full, and our side is set to auto select. Our side
always selects 100/half and if we hard code it to 100/full, we lose
connectivity. How can we get this to be 100/full? Is it a problem with
the cross-over cable in between?

Doug McIntyre 12-06-2011 11:33 PM

Re: Need help with port duplex settings
 
pfisterfarm <pfisterfarm@gmail.com> writes:
>We have a newly installed 4506e switch, which is uplinked to our
>upstream provider's ME3400 switch (CSME). The provider's switch is
>hard coded to 100/full, and our side is set to auto select. Our side
>always selects 100/half...


Which is exactly what the standards say should happen.
Not that this is what anybody expects, but it is what it is.

> and if we hard code it to 100/full, we lose
>connectivity. How can we get this to be 100/full? Is it a problem with
>the cross-over cable in between?


When you disable auto-speed, you also disable auto MDI-MDI/X detection.
Whatever cable you are using probably is the wrong one.

Perhaps the upstream provider handed you a port expecting a straight
through cable to save you future problems, and then you went and put a
crossover cable there anyway...



pfisterfarm 12-07-2011 02:23 PM

Re: Need help with port duplex settings
 
> Perhaps the upstream provider handed you a port expecting a straight
> through cable to save you future problems, and then you went and put a
> crossover cable there anyway...


Yes, turned out to be the wrong cable. We've done many, many similar
sites in the past and have always used a crossover cable, which I have
installed. Someone else did it on this particular site, and I assumed
(too much) that it was a crossover.

Sam Wilson 12-09-2011 11:15 AM

Re: Need help with port duplex settings
 
In article <2011120907555149338-hepcat@hepcathepcat>,
Paul Matthews <hepcat@hepcat.hepcat> wrote:

> On 2011-12-06 23:33:05 +0000, Doug McIntyre said:
>
> > pfisterfarm <pfisterfarm@gmail.com> writes:
> >> We have a newly installed 4506e switch, which is uplinked to our
> >> upstream provider's ME3400 switch (CSME). The provider's switch is
> >> hard coded to 100/full, and our side is set to auto select. Our side
> >> always selects 100/half...

> >
> > Which is exactly what the standards say should happen.
> > Not that this is what anybody expects, but it is what it is.

>
> It always surprises me that people seem to think forcing one end will
> make the other follow suit.


If you think of the setting as being "this is what I want - please do
the same" then it makes sense. It's the fact that it's "this is what
I'm doing and I'm not going to talk to you any more" that seems to be
unexpected.

> Negotiation has improved hugely, and now normally just works. Add i the
> auto MDI and I actually prefer to let switches sort it these days.
>
> Most of the negativity comes from te early days, where with a 3Com lan
> card and a 3Com switch, you had an evens chance of negotiation being
> successful. Those days are long gone.


We had different models of 3Com switch which resolutely refused to
negotiate a working link. That was long ago and I think the switches
concerned had come from different companies that 3Com had absorbed.

Sam

Rob 12-09-2011 12:36 PM

Re: Need help with port duplex settings
 
Sam Wilson <Sam.Wilson@ed.ac.uk> wrote:
>> Most of the negativity comes from te early days, where with a 3Com lan
>> card and a 3Com switch, you had an evens chance of negotiation being
>> successful. Those days are long gone.

>
> We had different models of 3Com switch which resolutely refused to
> negotiate a working link. That was long ago and I think the switches
> concerned had come from different companies that 3Com had absorbed.


But what is important is: it is all a thing of the past. It is not a
concern anymore.

But still, there are companies that keep this "thou shall set the ethernet
port to a fixed configuration and not use auto" in their standard practices,
thus causing extra maintenance effort and non-working setups, without any
advantage.

grinch 12-09-2011 12:42 PM

Re: Need help with port duplex settings
 
On 07/12/11 14:23, pfisterfarm wrote:
>> Perhaps the upstream provider handed you a port expecting a straight
>> through cable to save you future problems, and then you went and put a
>> crossover cable there anyway...

>
> Yes, turned out to be the wrong cable. We've done many, many similar
> sites in the past and have always used a crossover cable, which I have
> installed. Someone else did it on this particular site, and I assumed
> (too much) that it was a crossover.


IMHO setting anything auto is proof that you don’t understand networking
properly.

I have had numerous weird faults mainly with Video and Voip which have
been traced to this problem .I always lock things to some fixed setting
or other

If you force the switch port to 100 full then you can be sure that
everything that can connect to them must work at that setting and all
the cables are correct. And they are getting the bandwidth they are
paying for.

As a starting point cable wise ,any ports of the same type of device IE
switch router etc think crossover different device type think straight
..It is not an absolutely foolproof method but it is a start.



Tip here ,take a short length crossover cable with you at all times and
a cat5 straight through coupler. If you disconnect the cable and add it
you change to the other sort of cable . Add it to a straight and it
becomes a Xover and an Xover to an Xover becomes a straight.



--
Output certified microsoft free
Checked with OpenSuse 12.1

Doug McIntyre 12-09-2011 01:54 PM

Re: Need help with port duplex settings
 
Paul Matthews <hepcat@hepcat.hepcat> writes:
>Negotiation has improved hugely, and now normally just works. Add i the
>auto MDI and I actually prefer to let switches sort it these days.


Oh, I agree, I run thousands of ports in auto with no problems. Handoff
to customers, handoff to my servers all work with no issue.

But MOE type handoffs by the phone companies are typically all
set to hard code for speed/duplex for sub-gigabit speeds. That is
their standard and that is how it is.

>Most of the negativity comes from te early days, where with a 3Com lan
>card and a 3Com switch, you had an evens chance of negotiation being
>successful. Those days are long gone.


I never had any problems with 3com, but there was one specific cases
with Sun SPARC servers and Cisco switches that came up every now-and-then.
But last time I ever saw problems like that was back in the mid '90s.
By the late '90s, everything worked all the time for autonegotiation.

But that doesn't change the ingrained ideas that you *have* to force
duplex/speed on 100Mbps ports in many circles.. Even as recently as
the Cisco PIX era, the docs strongly recomended hard coding
duplex/speed, so usually whenever people brought in a PIX, I'd have to
match them on hardcoding duplex/speed.



Sam Wilson 12-09-2011 05:30 PM

Re: Need help with port duplex settings
 
In article <slrnje406h.592.nomail@xs8.xs4all.nl>,
Rob <nomail@example.com> wrote:

> Sam Wilson <Sam.Wilson@ed.ac.uk> wrote:
> >> Most of the negativity comes from te early days, where with a 3Com lan
> >> card and a 3Com switch, you had an evens chance of negotiation being
> >> successful. Those days are long gone.

> >
> > We had different models of 3Com switch which resolutely refused to
> > negotiate a working link. That was long ago and I think the switches
> > concerned had come from different companies that 3Com had absorbed.

>
> But what is important is: it is all a thing of the past. It is not a
> concern anymore.


Absolutely - it was just an extreme and rather ludicrous example.

> But still, there are companies that keep this "thou shall set the ethernet
> port to a fixed configuration and not use auto" in their standard practices,
> thus causing extra maintenance effort and non-working setups, without any
> advantage.


Yep - sad.

Sam

..

Sam Wilson 12-09-2011 05:36 PM

Re: Need help with port duplex settings
 
In article <CmnEq.51401$Oz7.12628@newsfe24.ams2>,
grinch <grinch@somwhere.com> wrote:

> On 07/12/11 14:23, pfisterfarm wrote:
> >> Perhaps the upstream provider handed you a port expecting a straight
> >> through cable to save you future problems, and then you went and put a
> >> crossover cable there anyway...

> >
> > Yes, turned out to be the wrong cable. We've done many, many similar
> > sites in the past and have always used a crossover cable, which I have
> > installed. Someone else did it on this particular site, and I assumed
> > (too much) that it was a crossover.

>
> IMHO setting anything auto is proof that you donąt understand networking
> properly.


Oddly I take the opposite view point, especially since autonegotiation
is mandatory for GigE. :-)

> I have had numerous weird faults mainly with Video and Voip which have
> been traced to this problem .I always lock things to some fixed setting
> or other
>
> If you force the switch port to 100 full then you can be sure that
> everything that can connect to them must work at that setting and all
> the cables are correct. And they are getting the bandwidth they are
> paying for.


If you lock the switch port to 100 full you can be sure that anything
you plug into it will have a duplex mismatch. For video and VOIP this
is likely cause all sorts of problems which will persist until either
you persuade the poor user that they must configured their system to 100
full, or you configure your switch to negotiate.

> As a starting point cable wise ,any ports of the same type of device IE
> switch router etc think crossover different device type think straight
> .It is not an absolutely foolproof method but it is a start.


Except for GigE when you don't need a crossover, and many other modern
systems which do auto-MDI.

> Tip here ,take a short length crossover cable with you at all times and
> a cat5 straight through coupler. If you disconnect the cable and add it
> you change to the other sort of cable . Add it to a straight and it
> becomes a Xover and an Xover to an Xover becomes a straight.


If you're going to use it for GigE then make sure you cross all four
pairs over.

Sam

..

Sam Wilson 12-09-2011 05:38 PM

Re: Need help with port duplex settings
 
In article <4ee21314$0$79795$8046368a@newsreader.iphouse.net> ,
Doug McIntyre <merlyn@geeks.org> wrote:

> But MOE type handoffs by the phone companies are typically all
> set to hard code for speed/duplex for sub-gigabit speeds. That is
> their standard and that is how it is.


We have a telco which insists on turning off negotiation for GigE links.
Sigh.

Sam

..


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