[3c509] N-Way Auto Negotiation and Full Duplex

[Donald Becker]

On Mon, 16 Sep 2002, Wm. G. McGrath wrote:

> Now it seems I am up against ethernet history. I am told that 509B
> full duplexing was developed prior to N-Way Autonegotiation.

Correct.  And pre-NWay full duplex is non-standard.

> So my
> switch, a D-Link DSS-8+, does not recognize the 509B as full duplex
> capable and seems to connect in half-duplex mode - that is the full
> duplex indicator led doesn't light. The card works but I'm not sure
> what mode it is in really.

The card is in full duplex mode.
The switch is in half duplex mode.
You have a duplex mismatch and will have bad performance and packet loss.

> >The "Full-Duplex/Collision" LED indicator depends upon LAN card
> >capabilities for full duplex or half duplex. 
> >If the attached device does not support auto-negotiation or has
> >auto-negotiation disabled, an auto sensing process is initiated to
> >select the speed and set the duplex mode to half-duplex.
> >(Pretty clear huh. :/)

Yup, very clear.  Ethernet is half duplex (technically CSMA/CD, but
informally "half duplex").  The only standard-conforming way to end up
with a full duplex link is through autonegotation.

> But more importantly, is there a work around. Can I manually set a
> parameter to activate nway autonegotiation? Is there some way to
> modify the driver to autonegotiate with the switch?

No.  The hardware must support autonegotiation.

> Does anyone know anything about old time full duplex and N-Way 
> autonegotiation?

Read
  http://scyld.com/expert/NWay.html

-- 
Donald Becker				becker@scyld.com
Scyld Computing Corporation		http://www.scyld.com
410 Severn Ave. Suite 210		Second Generation Beowulf Clusters
Annapolis MD 21403			410-990-9993