[CentOS] force 10 megabit full duplex

Sun Apr 16 21:42:13 UTC 2006
centos at 911networks.com <centos at 911networks.com>

William Warren wrote:
> William L. Maltby wrote:
>> On Sat, 2006-04-15 at 19:41 -0500, Ryan Lum wrote:
>>> Is the ethernet port in question connect to a switch?  Might try 
>>> forcing the
>>> port on the switch to 10 Mbit full duplex.  If it is on default the 
>>> switch
>>> will negotiate the speed.
>> Not if it's an old 3Com 3C509. They don't negotiate. I have a few of
>> those I use with an unmanaged switch. I was planning on someday seeing
>> if just forcing them to full duplex would work (hoping the switch was
>> smart enough to recognize the need: decent SMC with auto wire adjust ,
>> etc., so I'm hopeful). I "programmed" the eproms, but the Linux drivers,
>> in their infinate wisdom, force them back to half duplex. *sigh*.
> this is a dell PE850 with intel gigabit nics.

There are various scenarios with 10Mbps/full duplex:
1. 10/100 Hub: Not possible
2. Modern cheap switch [linksys/dlink...] On auto negotiate: The 
  card will send a 5bit: 1000Full, 100full, 100half, 10full and 
10half and the switch will take whatever is the highest that it has.

Why 10baseT usually because the wiring is Cat3 or poor wiring 
[leads in the wrong slot] or the wiring is too close to 
fluorescents with dying ballasts. 10baseT works with a twisted 
pair [the T in 10baseT]. Today all modern switches assume that if 
you use 10baseT is that's a twisted pair, therefore 10full is not 

No un-managed switch will negotiate to 10full. Never happened & 
will not happen. When 10baseT was implemented Cat3 was standard 
and you could not get 10full reliably. The drivers were not that 
great either, even the 3com drivers were lousy under DOS.

Today, the only way to get 10baseT full duplex is with a managed 
switch [Cisco and the likes or web managed interfaces] and locked 
on BOTH sides [the DTE and the DCE].

BTW, 1000baseT is ONLY full duplex and you will need the wiring 
to support the 8 leads. The wiring will have to be at least Cat5e 
or Cat6

When the network has to work