This tutorial describes how the switch forwards and also filters the MAC addresses. Learn just how the switch procedures incoming frames in addition to the species of frames which the switch always floods.

You are watching: When a switch receives a frame on a port and floods the frame, what does it do with the frame?

To send a big amount that data to various other PC in the network, the sender computer breaks the data in numerous smaller pieces and also packs each piece with the protocol details which the recipient PC needs to reassemble every pieces earlier into the initial data stream.

To know what else info each piece has or how the info is included to the piece or how the information is used to reassemble all pieces ago to the data stream, see this tutorial.OSI Layer version explained

The gadgets which work in the middle of the network and also connect the sender pc with the recipient PC likewise usethis details to process each item intelligently. Each piece, recognized as the frame, together with severalother information has the hardware attend to of the sender and receiver PC. The hardware deal with is known as the MAC address.

A switch works in the middle of the network. It connects many devices. It offers MAC addresses of the sender and also receiver devices to process the frame. When a switch receives a frame, that reads the resource address of the frame and stores it into a table recognized as the CAM table. This process is known as the Learning addresses.

To understand the Learning process in detail, examine this tutorial.How switch learns the MAC address

After saving the resource address in the video camer table, the switchreads the location MAC resolve of the frame and also finds an entry because that this resolve in the video camer table.If the video camer table has actually an entry because that the destination MAC address, the switch provides that entry to make the front decision. This procedure is well-known as the Forwarding frames. The below section explain this process in more detail through examples.

Frame forwarding and also filtering process

Above, we discussed the learning process before the forwarding process.But in reality, the forwarding process takes place prior to the learning process.

Forwarding the frames as soon as feasible is the key goal that a switch, and also you deserve to bet on it the the move achieves this goal really really fast. A switch deserve to start the forwarding process even prior to pulling the frame completely inside.

To learn much more about how quickly a move starts the framework forwarding process, friend can examine this tutorial.Switching methods and types explained

Switches usage a reasonably simple principle to forward a frame. This concept is the following.

Find the location MAC attend to of the incoming structure in the camer table and also if the resolve is obtainable in the table, front the structure from the port which is connected with the location MAC deal with otherwise front the frame from every ports except the port on which the arrived.


Let’s recognize this process in an ext detail v an example.

Suppose, in a network, 4 PCs are associated through a switch. PC-A sends a frame to the PC-B. The move receives this frame on the F0 interface. The switch reads the destination deal with of the frame and also finds that in the video camer table. Due to the fact that the cam table has no entry because that this destination address, the move floods this frame from every ports other than the harbor F0. As well as forwarding the frame, the switch additionally stores the source address in the electronic came table.


Now suppose, the PC-B responds come the PC-A through its frame. The switch receives this structure on the user interface F1. This time, by looking at the cam table, the switch knows wherein the PC-A is located. So, rather of flooding the frame out from every ports together it go earlier, this time the move forwards this structure only from the port (F0) i m sorry is associated with the PC-A. Very same as earlier, it also saves the MAC attend to of PC-B in the camer table.


Types that frames i m sorry are always flooded v the switch

There room three species of address; unicast address, multicast address, and also broadcast address. This address species respectively represent an individual end device, a group of devices and also all gadgets of the network. Frames sent on these addresses are respectively well-known as the unicast frames, multicast frames, and also the transfer frames.

Switch processes these frames as the following.

Unicast frames

To know which port is associated with which address, the switch supplies the cam table. Based on the electronic came table’s entries, a unicast deal with can it is in categorized right into two types; known unicast address and unknown unicast address. If the deal with is easily accessible in the cam table, that is a known unicast deal with otherwise that is one unknown unicast address.

Switch forwards a well-known unicast structure only indigenous the harbor which is directly associated to the destination deal with of that structure while the forwards an unknown unicast framework from all of its ports, other than the harbor on which the arrived.

In the above example: -

When PC-A sent a framework to PC-B, the destination resolve (2222.2222.2222) the the frame was unknown to the switch. So, the switch flooded this frame from every ports, except the harbor (F0) ~ above which it arrived.

When PC-B responded to PC-A, the destination address (1111.1111.1111) was known to the switch. So, the switch, rather of flooding the from every ports, forwarded the frame only indigenous the harbor which is connected with the destination address.

Switch floods a unicast structure only if the destination resolve of the framework is not well-known to the switch.

Multicast and also broadcast frames

Both multicast and broadcast addresses represent much more than one device. These addresses room the destination onlyaddresses and also cannot be provided as the source address. An end-device provides these addresses only as soon as it desires to send the same structure to a group of tools or all devices of the network.

For example, a network has 50 PCs and also one that them wants to send a structure to all PCs. The PC has two selections here; either create 49 (excluding self) unicast frames and sends one come each pc or produce a transfer frame and also send it come all. Since the second option is lot easier and faster, a PC constantly uses it.

A switch constantly floods multicast and also broadcast frames. That learns addresses by reading the source address ar of incoming frames. Due to the fact that both the multicast and broadcast addresses are never used in the source address ar of a frame, a switch never learns this addresses. And also since a switch never learns these addresses, it constantly floods the frames which have actually these addresses as the destination address.

See more: Which Of The Snowshoe Rabbit’S Unique Adaptations Help It To Survive Predation In The Taiga?

That’s all for this tutorial. If you like this tutorial, please don’t forget come share it v friends with your favorite social channel.