Layer 2 Switching

Hi….all network guys… we start with the type of switching because in every interview or troubleshoot the first question always is there like how a switch learns mac address? What is the function of layer 2 switchings?


What type of switching we used? What is the layer 2 and layer 3 switchings?

Today big names like Cisco, Juniper, HP, etc maker of the switch. all switch having the same function some of the configurations are different. Every switch switching data from source to destination with the help of the type of switching technology.

From this blog maybe you are basically satisfied and this is helping you with your bright knowledge. Switching is a process that data can be transferred from source to destination. Switches operated at layer 2 in the OSI model i.e. Data Link Layer.

There are three types of switching

  1. Layer 2 switching
  2. Layer 3 switching
  3. Multilayer switching

Now I can explain to you Layer 2 switching, In layer 2 switching data can be forwarded on the basis of layer 2 addresses.


Types of layer 2 switching

  1. Ethernet switch
  2. Frame relay switch
  3. ATM switch

Now-Again I can explain in brief Layer 2 Switching

  • Ethernet Switch: Data can be forwarded on the basis of MAC address (Medic Access Control)

The function of Layer 2 Ethernet switch:

  • Address learning
  • Filtering & Forwarding decision
  • Loop Avoidance

Layer 3 Devices can perform three types of switching

  • Process Switching: devices can perform routing lookup for each received packet.
  • Fast Switching: RP will lookup routing table for the first packet after that SE will generate a shortcut entry in the cache memory and for the next packet, SE will check short-cut entry and RP will get free.
  • CEF switching (Cisco express forwarding)

CEF create two table FIB and Adjacency table

  • FIB: it is a replica of the routing table.
  • Packet Rewriter: when a packet cross a layer 3 device, it will always respond to rewrite header checksum, layer 2 information, and TTL.

How switch learn mac address

  • Dynamically: switch can learn mac address automatically of devices in its cam table.
  • Statically: we can manually enter the mac address of devices in the cam table. we can generate a cam table manually to stop unknown unicast broadcasting.

Thanks for reading. This is the basic study about layer 2 switching how it works or what type of table has formed in switch RAM. In the next blog, we will show how to switch learn MAC add and How to flow frame in a switch to switch & Function of CAM table.