[c-nsp] WS-X6748-GE-TX auto negotiation anomalies

[Geoffrey Pendery]

This feature was the subject of much debate on my team, as we desired
to put in triple-speed blades but only allow 10/100 autoneg from end
stations.
We didn't end up doing it in prod, but we did get confirmation it was
possible, and the syntax required.
I currently don't have a working lab to verify, but the CLI parser at
least accepts my syntax:

config t
interface Gig 1/1
 speed auto 10

Should achieve "Case A" on the 6748.  Usual caveats apply (depends on
code you're running, may not work at all due to bugs or hardware
limitations, etc etc etc).


-Geoff


On Fri, Apr 9, 2010 at 4:19 AM, Will Hargrave <will at harg.net> wrote:
> On 08/04/10 17:42, Jason Lixfeld wrote:
>
>> 'speed auto 10' would be an acceptable 6748 workaround, but even that
>> behaves differently on the 6748 vs ME/3550.  The 6748 needs two speeds for
>> speed auto ie:  speed auto 10 100 whereas the ME/3550 need only one ie:
>> speed auto 10
>
> Right, so what you are doing here are two distinct things - it's confusing
> because of the disparate platforms:
>
> Case A: changing the capabilities advertised using autoneg to only advertise
> 10mbit speed
>
> Case B: turning off autoneg altogether.
>
> In the case of B, without autoneg visible the remote end cannot sense duplex
> (it can of course sense speed) and thus you get the correct speed but half duplex.
>
> This is because Cisco didn't put enough twiddly knobs in the CLI on 6500 to
> configure what you want. I agree it is annoying, lots of cheaper devices allow
> you to independently:
>
> a. turn on or off autoneg
> b. turn on or off auto-mdix
> c. select capabilities (speed, duplex, flow control) advertised using autoneg
> d. select capabilities (speed, duplex, flow control) actually accepted
>
> I feel your pain; the lack of configurability invariably leads to people just
> turning off autoneg altogether, which is worse.
>
> Will
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