[c-nsp] full duplex mismatch speed - dynamips

Andriy Bilous andriy.bilous at gmail.com
Thu Aug 19 14:27:43 EDT 2010


Oh, believe me, you're not alone. We have actually a cable guy with a
piece of paper on the wall behind picturing a road sign - crossed red
circle with the word "auto" inside.

On Thu, Aug 19, 2010 at 6:52 PM, John Neiberger <jneiberger at gmail.com> wrote:
> On Thu, Aug 19, 2010 at 10:07 AM, Adam Armstrong <lists at memetic.org> wrote:
>> On 17/08/2010 23:50, Justin M. Streiner wrote:
>>>
>>> On Tue, 17 Aug 2010, Alessandro Braga wrote:
>>>
>>>> Verify duplex and speed configurations on interface, the rule is:
>>>> autoXauto, forcedXforced. If problem not solve, disable cdp.
>>>
>>> Also, while auto speed/duplex negotiation is fine for user
>>> workstation/PC ports in most cases, I recommend against using it on your
>>> network infrastructure if you can help it.
>>
>> This is horribly terrible advice.
>>
>> Autonegotiation should always be used as default, nailing should be the fix
>> for when things don't work, and where very old devices don't do autoneg
>> properly.
>>
>> Note that for gigabit, autonegotiation is MANDATORY.
>>
>> adam.
>
> Adam, you are my new best friend. I've been saying this for the past
> few years and people still think I'm crazy. I flat out refuse to
> manually configure speed and duplex for someone unless it is
> demonstrated (or I can verify) that a duplex mismatch is actually
> happening or there is some other extenuating circumstance that
> requires it.
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