Switching basics!

The third video is quite an interesting one, however, it does take a little while to get into the more "interesting" stuff. Again, it's mostly all theory and starts off listing the layer 1 devices and the first layer 2 device, a bridge:

• A repeater simply amplifies the transmission
• A hub is basically a repeater with multiple ports
• A bridge connects two hubs together

Anything connected to a hub is considered to be in the same collision and broadcast domain. They also depend on CSMA/CD.

A bridge separates two hubs. This splits the collision domain into two, however, there is still only one broadcast domain.

Anything connected to a switch is considered to be in it's own collision domain but they will all be in the same broadcast domain (assuming all in the same VLAN).

Creating VLANs create new broadcast domains as traffic from one VLAN cannot reach another VLAN without the intervention of a layer 3 device, most likely a router.

Cisco switches use STP (spanning tree protocol) to prevent switching loops and is enabled by default. STP determines a loop-free path for frames and ports that are not on that path will be placed into blocking mode.