[c-nsp] full duplex mismatch speed - dynamips

[Justin M. Streiner]

On Thu, 19 Aug 2010, Adam Armstrong 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.

For 1000baseT, yes, autoneg support is mandatory.

I'll qualify my original statement.  My FE experience is somewhat dated,
but at that time, enabling autoneg would also often set the evil bit.  It
created more problems than it solved.

It's been 5+ years since I had to worry about speed and duplex autoneg to
any significant extent in my network infrastructure since the place I 
moved to was already GE over fiber when I came in and much of it has been 
upgraded to 10G since.  The only time I worry about speed and duplex 
autoneg anymore is on end-user ports that don't always link up the way one 
would think they should, and this more often than not ends up being 
caused by older NICs and/or sketchy drivers.

jms