Networking Nuggets – Hub vs Bridge vs Switch

Sriram S
Networking
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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?

  1. A Hub is a networking device that the physical layer (Layer 1) of the OSI Model.
  2. By physical layer, I mean that a Hub operates purely on the electrical signals that flow through our networks.
  3. 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.
  4. Since a Hub repeats the frame, it is also known as a repeater.
  5. Limitation - high traffic can bog down a hub since every frame is replicated.

What is a Bridge?

  1. Bridge is a more intelligent networking device when compared to a Hub.
  2. A Bridge has two ports and was designed to bridge two LAN segments.
  3. Bridge interprets the electrical signals as an incoming frame on one of its ports.
  4. Then it looks at the destination address (MAC address) encoded in this incoming frame and decides whether to forward the frame or drop it.
  5. For this reason, a Bridge is considered as a data link layer (Layer 2) device.
  6. Limitation - since it has only two ports, a bridge cannot be widely used to connect end hosts and devices.

What is a Switch?

  1. A Switch is a Bridge with more than two ports.
  2. Switches and Bridges use MAC address for determining the destination port for an incoming frame.
  3. A Switch is a more scalable and practical networking device
    • A switch overcomes the limitations of both Hub and a Bridge
  4. Switches are much more widely used today when compared to Hub and Bridge.

YouTube Video