Network switches

What is a network switch?

A network switch connects two or mode devices together so that they can send packets to each other.

Devices that can be connected via switch are:

• computer
• printers
• wireless access points i.e. routers

Diagram:

Switches:

• have many network interfaces/ports
• provides connectivity to hosts within the same LAN (Local Area Network)
• do not provide connectivity between LANs/over the internet.

What is LAN (Local Area Network)?

A local area network (LAN) is a group of connected devices within a close physical proximity.

Example of LAN network is home WIFI networks. Your home wifi connects different devices within your home via switch.

A LAN requires:

• a router
• eithernet cables or a wifi hotspot
• switch
• host devices

There is only one requirement to setup a LAN is that the connected devices are able to send or recieve data.

How network switch function?

Network switches can operate at either:

• Layer-2: OSI or data link layer
• Layer-3: network layer

Layer 2 switch forwards data based on the destination MAC address, while layer 3 switch forwards data based on the destination IP address.

Layer 2 network switches maintain a table in memory to remember which device is connected to which port. Let's take an example to understand:

Let say that we have 3 computers which are connected to layer 2 switch. Let's assume that:

• Computer A is connected to Port 1
• Computer B is connected to Port 2
• Computer C is connected to Port 3

We just turned on the switch at this point switch does not know anything about mapping and table is clear.

Here is how memory table look like in the beginning:

When switch is turned on it has not created a memory table and it does not know where computer A, B and C is connected. It does not know device mac address.

Let say that computer A sends message to computer B. A message is first recieved by switch and it notes computer A's mac address and connected port.

it then forwards this recieved message to all devices in a network (except computer A) because this is where message came from.

This process is known as "flooding". When computer B replies, it records computer B's mac address and port as well.

Now, switch CAM table knows where Computer A and Computer B are in a network and it also know their mac address and port where they connected.

Different types of switches:

• KVM Switches
• Managed Switches
• Unmanaged Switches
• Smart Switches
• PoE Switches
• Modular Switches
• LAN Switches