Dual-port NIC

Stefan Bethke stb at hanse.de
Tue Oct 15 14:19:08 BST 2002

On Tue, 15 Oct 2002, Andrew wrote:

> I have been given a dual port network card (Accton EN1207TX, I think -
> dmesg says it's using the de driver). Has anyone got experience with these
> things? That is to say, can they do anything a single port card can't do?
> My hope is that each port can be used independently (one is 10Mb, one is
> 100Mb) so my (hypothetical) NAT box only needs one card rather than two. I
> guess I mean, can each port have a unique MAC address?

Seems unlikly to me. I guess it's an older 10/100 card, with two seperate
tranceivers and codecs for 10 and 100 Mbit/s operations. If you look
closely at the PCB, you might find space for a BNC connector for 10Base2
(cheapernet), if my theory is right.

Newer 10/100 cards have a combined transceiver and codec (the "phy" chip),
and thus only one RJ-45 connector.

Under this theory, your card has only one controller, and thus can operate
at either 10 or 100 Mbit/s, and use only one of the ports at a time.

> I've looked on the web but can't find any info on dual-port cards.

That's because there aren't (to the best of my knowledge) any multi-port
controller chips; the multi-port cards have a PCI-PCI bridge and a couple
of seperate controllers on them. Accordingly, to FreeBSD (or most other
OSes) they seem to be completely different controllers, as if they were on
seperate cards. So if your board were a dual-port NIC, you would have a
de0 and de1 interface (ifconfig -a will show).


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