Switches

Switches operate using MAC addresses found in the Ethernet header of the traffic.

Switches have CAM (Content Addressable Memory) tables that map a physical port to MAC addresses.

  • Switches populate a CAM table by looking at the Ethernet header and determining the SOURCE address of traffic arriving on that port.
  • It is possible the table maps multiple MAC Addresses to the same physical port (e.g. Switch port is connected to a hub with multiple hosts).

Switches check the DESTINATION MAC address against the MAC table.

  • If the address is mapped to a port, forward it out that port.
  • If no mapping, forward it out ALL ports EXCEPT the one it was received on - Traffic usually gets a response, and the MAC table will be updated normally when that traffic is seen.

If the DESTINATION MAC is a broadcast address, then forward it out ALL ports EXCEPT the one it was received on.

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