Here is an overview of three basic networking devices - Hub, Bridge and a Switch. This blog and the related YouTube video at the end, will be useful for upcoming topics related to virtual networking such as Linux Bridge and Open vSwitch.
What is a Hub?
- A Hub is a networking device that the physical layer (Layer 1) of the OSI Model.
- By physical layer, I mean that a Hub operates purely on the electrical signals that flow through our networks.
- An incoming frame from any port is broadcast to all other ports in a hub.
- The host or device attached to the port decides what to do with the frame.
- Since a Hub repeats the frame, it is also known as a repeater.
- Limitation - high traffic can bog down a hub since every frame is replicated.
What is a Bridge?
- Bridge is a more intelligent networking device when compared to a Hub.
- A Bridge has two ports and was designed to bridge two LAN segments.
- Bridge interprets the electrical signals as an incoming frame on one of its ports.
- Then it looks at the destination address (MAC address) encoded in this incoming frame and decides whether to forward the frame or drop it.
- For this reason, a Bridge is considered as a data link layer (Layer 2) device.
- Limitation - since it has only two ports, a bridge cannot be widely used to connect end hosts and devices.
What is a Switch?
- A Switch is a Bridge with more than two ports.
- Switches and Bridges use MAC address for determining the destination port for an incoming frame.
- A Switch is a more scalable and practical networking device
- A switch overcomes the limitations of both Hub and a Bridge
- Switches are much more widely used today when compared to Hub and Bridge.