Introduction
ARP stands for Address Resolution Protocol, which is the main protocol that enables communication between two devices on the same network.
WORKING
When the client wants to send data to a device on the same network and knows the IP address of the device but doesn’t know the MAC address the ARP protocol comes into play. When the user sends the data the device, the ARP protocol is triggered first, retrieves the MAC address, and then the data is sent to the device using the MAC address.In More Depth:When the user sends data without knowing the MAC address but knowing the IP address, the first thing that happens is:
1. ARP Request: The client checks its ARP cache to see if it is already knows the MAC address for the IP. If not, it sends an ARP request to the network, broadcasting it to all devices using the MAC address ff:ff:ff:ff:ff:ff. This request is sent to every device within the network.
2. ARP Reply: The device with the matching IP address replies with its MAC address.
3. Data Sent: Once the MAC address is obtained, the data transfer begins to that MAC address.
This flow ensures the client can send data to the correct device within the same network.
Why MAC and NOT local IP?
ARP makes this communication possible by obtaining the receiver’s MAC address. Now, you might wonder: why can’t the local IP address be used to send data between two devices within a network? An IP address is a logical address used to identify the device within the network and to indicate where the device is located. However, it can’t be used for actual data transfer. When data is passed down to the data link layer, which is closer to the hardware, the MAC address is required for the actual data transfer.
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