data link layer source and destination addresses

Data Delivery from the source device to a destination device is the primary responsibility of the network layer and data link layer. Protocols at both layers contain a source and destination address, but their addresses have different purposes. Understanding data link and network layer addresses is crucial for mastering communication between devices. These addresses—MAC at Layer 2 and IP at Layer 3 of the OSI model—form the foundation of how data travels across networks. This comprehensive guide explores their roles, differences, and modern applications, including the rise of IPv6 and 5 G. Whether you’re a network administrator or a curious learner, this article will empower you with essential knowledge.

What Are Data Link Layer Addresses?

Data link layer addresses, commonly known as MAC (Media Access Control) addresses, and also known as physical addresses, operate at Layer 2 of the OSI model. These 48-bit hardware addresses are unique to each network interface card (NIC) and are hardcoded by manufacturers. They facilitate direct communication between devices on the same local network, ensuring frame delivery from one NIC to another.

It has a different role from the IP address. It delivers the data link frame from one network interface card to another on the same network. Before an IP packet is sent over a wired or wireless network, it is encapsulated in a data link frame and transmitted over the physical medium.

The figure below illustrates the data link layer address, or L2 address. As the IP packet travels from host to router, router to router, and finally router to host at each point, the IP packet is encapsulated in a new data link frame. Each data link frame has the source data link address of the NIC card sending the frame and the destination data link address of the NIC card receiving the frame.

In layer 2, the data link protocol is only used to deliver the packet from NIC to NIC on the same network. The router removes the Layer 2 information it received on one NIC and adds new data link information before forwarding out the exit NIC on its way toward the final destination. The IP packet is encapsulated in a data link frame that has data link information, including:

• Source data link layer addresses – The physical address of the device’s NIC sending the data link frame.
• Destination data link layer addresses—The physical address of the NIC receiving the data link frame. This address is either the next-hop router or the final destination device.

Understanding Network Layer Addresses

Network layer addresses, primarily IP addresses, function at Layer 3 of the OSI model. These logical addresses enable end-to-end communication across different networks, allowing routers to forward packets globally. In 2025, the shift to IPv6—offering 128-bit addresses—addresses the IPv4 exhaustion issue, supporting billions of devices in the IoT era.

Network Layer addresses deliver the IP packet from the source device to the destination device.  The destination may be on the same network or may be on a remote network. An IP address is also known as the network layer address. The IP address is also known as a logical address.  Any IP packet contains two network layer addresses:-

• Source IP address– The IP address of the sending device and the packet’s source.
• Destination IP address– The IP address of the receiving device and the packet’s final destination.

The figure below illustrates the source and destination IP addresses in the packet sent over the network.

How Data Link and Network Layer Addresses Work Together

Data transmission involves both layers working in tandem. The network layer encapsulates IP packets, which the data link layer wraps into frames with MAC addresses. The Address Resolution Protocol (ARP) resolves IP addresses to MAC addresses on the local network, a critical process in 2025’s dense device environments.

• The IP packet is encapsulated in a data link layer frame. Data link layer addresses are used for delivery on a single physical network, while network layer addresses are used for delivery across multiple networks.

Key Differences: MAC vs. IP Addresses

• MAC Address: 48-bit, physical, local network scope, unchanging.
• IP Address: 32-bit (IPv4) or 128-bit (IPv6), logical, global scope, configurable.
• 2025 Insight: With 5G networks, dynamic IP assignment, and virtual MACs enhance flexibility, though security remains a concern.

Common Addressing Problems and Solutions in 2025

Networking addresses face modern challenges:

• ARP Cache Issues: Clear cache or use static ARP entries to resolve conflicts.
• IPv4 Exhaustion: Migrate to IPv6 with dual-stack configurations.
• Security: Implement MAC filtering and IPsec for protection.

Conclusion

Mastering data link and network layer addresses is essential for navigating 2025’s complex networks, from 5G to IoT. MAC and IP addresses, working together, ensure seamless communication, with IPv6 paving the way for future growth. Stay ahead with NetworkUstad’s updates and explore related topics like the OSI model.