Basic Switch Logic

The primary role of a switch is to get frames from point A to B on a LAN. It does this by examining Source and Destination MAC addresses. Not unlike a router which instead uses IP addresses.

EXPAND ON THE FOLLOWING:

• Forward or Filter frames based on MAC address
• Learn and fill MAC / CAM table based on incoming MAC address
• Prevent Layer 2 loops with STP

• Switch receives / examines frame

• Is the frame's source MAC in the table?
  • NO: Add source MAC to table with associated port #

• Is the frame's destination MAC in the table?
  • NO: Flood frame out all ports in same VLAN except the port it originated from.
  • YES: Forward frame out appropriate port.

• If destination MAC is unknown | broadcast | multicast
  • Flood frame out all ports in the same VLAN except the port it originated from.

AKA, not sending the packet out X interface. Port Security is a good example of this.