we got a strange task from one of our customers. As you will see it is a really individual solution which is asked by the customer:
He produces a box which includes a 2-Port-Switch with just ONE MAC-Adress and only one IP-Adress can be configured on this box. Now packets should be sent to two different destinations (pls see topolgy.jpg) from both ports. If I connect this box with two LAN-cables in a Cisco 3400, the switch gives me MAC-Adress error because it recognizes that one MAC-Adress can be found on two different physical ports. I have tried to find a solution on Layer 2 and on Layer 3 but without success.
Regarding Layer 3 solution we will get the problem that both destinations can be reached but the reply packets only go one way back to the box. The Packets take the way in which the box is situated.
My only solution is using two switches. The customer wants to connect several of these boxes to the switch. Please have a look on the attachment and the problem should become more clear.
Would be nice if anyone has an idea how to solve this problem with just one L3-Switch.