@Ananth On a LAN, we use Ethernet and each device has a built in MAC address. You don’t have to configure the MAC address yourself. Let’s say you have two computers connected to a switch. These computers will have a MAC address, it comes with their network cards.
These computers however don’t communicate directly with Ethernet, they use IP instead. You’ll have to configure an IP address on each computer and it has to be in the same subnet. When ComputerA wants to send something to ComputerB, it will create an IP packet with its own IP address as the source and the destination will be the IP address of ComputerB. This IP packet will then be embedded in an Ethernet frame and forwarded. The switch will switch it to ComputerB.
https://networklessons.com/cisco/ccna-routing-switching/introduction-to-the-osi-model/
If you use routers in between, it’s a different story. I have an example here:
https://networklessons.com/ip-routing/introduction-to-routers-and-routing/
@Sinan Best to check the interface status for this:
https://networklessons.com/switching/troubleshooting-interfaces/
Rene