Used to be called “bridges.” Recall that there are really three types of network equipment:

  1. Hubs/Repeaters – Layer 1 devices that just forward everything blindly, including collisions/errors.
  2. Bridges/Switches – Layer 2 devices that flood only broadcasts but has the capability to learn where unicast frames go.
  3. Routers – Operate at layer 3. Some routers are also switches.

Switches can store information on where certain hosts are via a bridge table. ┬áThis table lists the MAC address and the associated port. Multiple MAC addresses could be assigned to a single port (For example when you’re daisy chaining switches). This is called adaptive learning.

Unicast Segmentation – Switches can limit which hosts can hear unicast frames.

Collision Domain – Not usually a problem these days.

Broadcast Domain – Segment where broadcast frames can be heard.

Store-and-forward – Traditional approach with CRC checks.

Cut-through Forwarding – The switch will just look at the destination MAC and send frames directly. No CRC checks.