[eepro100] eepro100 in 10Mbit mode

[Donald Becker]

On Fri, 21 Jun 2002, Amit Kucheria wrote:

> I am trying to create a network where in the edges are 100Mbit and the
> core is a throttled 10Mbit as follows:
>                       |              |
>    100Mbit            |     core     |              100Mbit
>   |*******| <-------->|   |*******|  |  <-------> |*******|
>    switch             |    switch    |             switch
>                       |   /   |   \  |
>                       |  /    |    \ |
>                       | R1    R2   R3|
>                       |              |
>   |-- edge ------|--------- core -------------|--- edge ------|
>
> R1, R2 and R3 are 3 routers containing eepro100 cards connected to a
> Netgear FS105 100Mbit core switch. I would like to throttle these
> interfaces to 10Mbits so that the effective throughput of the network
> becomes 10Mbit and _queuing_ occurs.
>
> But on using mii-tool to force these interfaces to 10baseT-FD, there are
> _many_ collisions on the core switch which kills even a 5Mbit flow to
> 3Mbit. I have tried 10baseT-HD too, but the collisions still seem to
> occur. Is there something fundamentally flawed in this design?

You are forcing the interface to full duplex?
Unless you link partner is also forced to full duplex, you will
encounter network errors and serious performance problems.

I never recommend forced full duplex.  If you don't have autonegotiation
on an Ethernet link, use standard Ethernet (CSMA/CD, "half duplex").

If you want to limit the negotiated speed, use the '-A' option to the
mii-diag program to limit the advertised capabilities:
      http://www.scyld.com/diag/index.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