how to design a dual port ethernet?

You can look at the AT912SAM9261-EK schematics which has an external DM9000E Ethernet controller. If you just want to forward most packets coming in on one port to the other without any processing/filtering then a 3 port switch from Micrel would probably do the job

How about if I want to bring packets in one interface, process them, and send them out the other interface?

Thanks, Tom

Maybe I'm missing something here, but...

• Two Ethernet controllers on a shared bus

• One extra MCU pin to address them uniquely

• Read from one, flip the address line, write to the other

Asix AX88796L, Davicom DM9000, SMSC 91C111, and Micrel KSZ8841 would be suited for the job - they're the only 10/100 non-PCI controllers on the market. Micrel offers a 2-port version with an integrated switch; you might be able to set this up to manipulate traffic between the ports.

Cheers, Richard

The ADMtech/Infineon ADM5120 has 4 Switched Ports and an Upstream Port. Edimax uses this chip in quite some products and there are also Linux ports available.

Use the internal interface for one of the ports and the external DM9000E for the second port. The AVR32 based AT32AP7000 has dual Ethernet so this could be simpler to use.

for

and then sent to the other ethernet port,so i have to build the system wit SDRAM and FLASH,now i have no Example to reference,so i don't know how t design the PCB.where can i get the PCB design Example?

If you buy the STK1000/STK1002 development kit, then the schematics this has both Flash/SDRAM and dual Ethernet. Alternatively you can talk to your friendly Atmel distributor which could just burn you a copy of the CD. It is

Alternatively you can cut out the DM9000E schematics from the AT91SAM9261EK and add to the schematic for the AT91RM9200-EK. This may or may not require changes to u-boot and definitely you need to reconfigure the Linux

Any recommendations on where to buy the STK1000? I can't find it on digikey. Is it even available yet?

Thanks, Tom