Overview
This lecture explains how MAC and IP addresses function together in networking and introduces the Address Resolution Protocol (ARP) as the bridge between them.
MAC and IP Addresses in Networking
- MAC addresses operate at the data link layer, providing unique hardware identification.
- IP addresses operate at the network layer, allowing logical routing between devices.
- Both address types are necessary for network communication.
The Role of Address Resolution Protocol (ARP)
- ARP is used to discover the MAC address associated with a specific IP address.
- Before sending data, an IP datagram must be encapsulated in an Ethernet frame with the correct destination MAC address.
- Every device maintains a local ARP table mapping IP addresses to their corresponding MAC addresses.
ARP Operation Process
- If a destination IP is not in the ARP table, the device sends a broadcast ARP message to all devices on the local network.
- The broadcast ARP message uses the MAC broadcast address (all Fs).
- The device with the matching IP address responds with its MAC address in an ARP response.
- The sender receives the MAC address, updates its ARP table, and includes the address in the Ethernet frame for delivery.
- ARP table entries expire after a short time to adapt to changes in the network.
Key Terms & Definitions
- MAC address — A unique hardware identifier for network devices at the data link layer.
- IP address — A logical address used to identify devices at the network layer.
- ARP (Address Resolution Protocol) — A protocol that maps IP addresses to MAC addresses.
- ARP table — A local table storing IP and MAC address associations.
- Broadcast ARP message — A network message sent to all devices to request the MAC address for a specific IP.
Action Items / Next Steps
- Review the ARP message exchange process and typical ARP table behavior.
- Study how ARP supports communication between network layers.