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 From:  Chris Buechler <cbuechler at gmail dot com>
 Cc:  "m0n0wall at lists dot m0n0 dot ch" <m0n0wall at lists dot m0n0 dot ch>
 Subject:  Re: [m0n0wall] Many collisions on the WAN interface
 Date:  Sun, 8 Jan 2006 16:05:43 -0500
On 1/8/06, sil <silverjp1 at gazeta dot pl> wrote:
>
> I've replaced the Nics with a 3com 509 isa for wan and a realtek 8139
> for the lan side.
> On the wan the nic is operating in half duplex at 10Mbit while on the
> lan in fullduplex at 100Mbit and there aren't any errors or collisions.
>

While the Realtek NIC's, especially the older ones, are pretty bad
(with any OS), it's basically impossible to have a half duplex
connection and no collisions unless you have a very light network
load.  With full duplex, you should never see any collisions unless
you have a problem (duplex mismatch typically, causing late
collisions).

When only one side or the other of a network connection can talk at
once (half duplex), with any substantial network load, periodically
they're both going to talk at exactly the same time.  That's what
causes a collision.  The only way to avoid this is to have network
devices that use full duplex.

-Chris