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  • Hub

  • Switch

  • Router

Hub

  • A very basic device that connects multiple computers in a device
  • Takes the incoming data from one port and broadcasts it to all the other ports, regardless of the destination
  • Works at Layer 1(Physical layer) only => No knowledge on MAC address => forwards everything to every node
  • Drawbacks:
    • Causes collision
    • Not intelligent, no filtering

Switch

  • Smarter than hub, forwards data only to the specific device (MAC address) it is meant for
  • Works at Layer 2(Data link layer) => It have MAC address => forwards message to the recipient only
  • Maintains a MAC address table to know which device is connected to which port
  • No collisions: by creating dedicated paths => No collision domain
  • If destination MAC address is FF.FF.FF.FF.FF.FF, then the message will be broadcast-ed to everyone => Broadcast domain

Router

  • Connected difference networks together and routes packets based on the IP address
  • Works at Layer 3(Network layer) => Has MAC address and IP address
  • Can assign IPs (DHCP), provide NAT(translate private IPs to public IPs and vice versa)
  • Used to connect LAN to internet

Network Domains

Collision-Domain

  • Its like a one-lane hallway => at a time only one man can walk through it. If more than one walks, collision occurs.

Broadcast-Domain

  • Its like a single room => If a person shouts, all others in the room has to stop and listen even though its not for them.

Hub - All devices connected to the hub are in the same one-lane hallway. When one PC sends a signal, all other PCs should wait. If not, the data packets collide. Makes the network slow and inefficient => A large collision domain - When a PC connected to the hub sends a message, it will be send to all other PCs connected to it irrespective to the receiver. => A large broadcast domain

Switch - Each port on a switch is its own private one-lane hallway to the device connected to it. Therefore multiple PCs can communicate simultaneously without collision - If the recipient is unknown, the message is broadcast-ed to all the devices connected to it => A large broadcast domain

Router - Similar to switch: each port in a router has its own collision domain. There won't be collision between devices connected to different ports of the router - Messages received will be sent to the target port only, not broadcast-ed to all ports. A router be default does not forward a broadcast message.

Hub Switch Router
Collision Domain ✘ ✔ ✔
Broadcast Domain ✘ ✘ ✔