Re: duplex negotiation

On Mar 20, 9:38 pm, Jim Allen <nos...@xxxxxxxxxxx> wrote:
On 19 Mar 2007 16:04:19 -0700, "flamer die.s...@xxxxxxxxxxx"



<die.s...@xxxxxxxxxxx> 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/tech/tk389/tk214/technologies_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.

.

Relevant Pages

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