1000BaseT NIC to NIC

1000BaseT NIC to NIC

Post by ch.. » Mon, 16 Jun 2003 13:29:38









>> > >1000BASE-T will work with either a straight-through or a 10/100-style
>> > >crossover. The standard includes a mechanism for detecting which pair is
>> > >which, and connecting them to the appropriate channel.

>> > While this is in the IEEE standard, it is optional.  Not all 1000BT
>> > nics or transceivers support autocrossover or autopolarity.  For
>> > example Cisco GBICS don't.

>> While I understand that the feature is optional, I know of NO 1000BASE-T
>> silicon that does not implement autocrossover. I can't imagine why Cisco
>> GBICs would not provide this capability, unless they have intentionally
>> disabled the feature (or they are using non-merchant silicon, which I
>> doubt).

>an example of something from Cisco which certainly *implies* that you
>need a crossover is
>http://www.cisco.com/en/US/products/hw/switches/ps646/products_instal...

>though if you read it very carefully and try to parse it I'm not sure
>Cisco actually is insisting on a crossover - the words that imply a
>crossover is necessary appear to be cut and paste from 10/100 (and
>unlike e.g. HP, no Cisco switches that I know of have auto MDI-X on
>their 10/100 ports).

Perhaps I should have said that I've never gotten Cisco 1000BT gbics
to autocrossover when using them to connect two switches together.