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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

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.