In the switched-Ethernet network below, find two packet transmissions so that, when a third transmission AD occurs, the packet is seen by B (that is, it is flooded out all ports by S2), but is not similarly seen by C (because it is forwarded to D, not flooded, by S3). All forwarding tables are initially empty, and each switch uses the learning algorithm of 2.4 Ethernet Switches.

 B C   AS1S2S3D 

Hint: Destination D must be in S3s forwarding table, but must not be in S2s. So there must have been a packet sent by D that was seen by S3 but not by S2.