Understanding Physical and Logical Addressing

Planning & Conceptual Understanding

A MAC address is a unique identifier in a device’s Network Interface Card (NIC). It is considered a physical address because it is directly connected to the hardware of the NIC. Instead of changing from network to network, the MAC stays the same no matter where the device goes. This allows devices on the same local network to identify each other at the data-link layer. A MAC address identifies the device on a local network, while an IP address identifies a device across the entire internet.

A NIC showing the Ethernet port, main controller chip, and PCIe connector.

A NIC showing its PCIe connector, Ethernet port, main chip area, and printed MAC address label.

• The Ethernet port (RJ-45 jack) is where the network cable plugs in
• The PCIe connector is connected to the motherboard, providing power and allowing data transfer
• The Controller chip is the IC that handles network processing
• The MAC address label is the printed sticker with the MAC value

Understanding MAC Address Structure

Full MAC Address	OUI (first 3 pairs)	Vendor / Company Name	Type of Vendor (physical, virtual, or both)
F0:18:98:AA:BB:CC	F0:18:98	Apple, Inc.	Physical Vendor
3C:5A:B4:11:22:33	3C:5A:B4	Google, Inc.	Physical Vendor
60:45:BD:12:34:56	60:45:BD	Microsoft	Physical Vendor
A4:BA:DB:22:33:44	A4:BA:DB	Dell Inc.	Physical Vendor
04:1A:04:55:66:77	04:1A:04	WaveIP	Physical Vendor
00:50:56:AA:BB:CC	00:50:56	VMware, Inc.	Physical Vendor
52:54:00:12:34:56	52:54:00	Not Found - Virtual Machine	Virtual Vendor

Most of the vendors in the table were physical hardware companies like Apple, Google, Dell, and Microsoft, which all have their own clearly registered OUIs. Virtualization companies like VMware also need registered OUIs because their virtual NICs must behave like real hardware and still require unique identifiers on a network. Even when an OUI wasn’t found, it still represented a block reserved for virtual machines, showing how VMs generate MAC addresses differently from physical devices. This activity helped me understand that MAC addressing works the same at Layer 2 for both physical and virtual hardware, and that the OUI tells who created or assigned the network interface.

Connecting the Physical and Digital: Interpreting MAC Address Structure

On Ubuntu VM

MAC address: 32:9e:41:5a:ae:94 • OUI: 32:9e:41 • Device Identifier: 5a:ae:94

On MAC Terminal

MAC address: 14:98:77:6f:58:9d • OUI: 14:98:77 • Device Identifier: 6f:58:9d

The OUI

The OUI is the first three bytes of a MAC address and represents the specific organization that created or assigned that address, effectively linking the NIC to its manufacturer because each company must register its own unique OUI. OUIs have to be globally unique so that no two vendors accidentally produce overlapping MAC addresses, which would cause network conflicts and make it difficult for devices to communicate. Even in a virtual machine, the virtual NIC still needs a vendor prefix so the MAC address follows proper formatting. Virtualization platforms register their own OUIs so the MACs they generate won’t collide with those from physical hardware or other virtual environments.

Device Identifier

Each NIC needs a unique device identifier so the network can tell devices apart and know exactly where to send data. No two devices on the same LAN can share a MAC address because switches use MACs to map which device is connected to which port, and duplicates would confuse the switching. This uniqueness ensures that Ethernet frames are delivered to the correct destination without being misrouted or lost.

Compare Virtual vs Physical MAC Addresses

The MAC address on the physical NIC is attached directly to the hardware. In the VM, the MAC address was generated by the virtualization software, which assigns a virtual MAC to the virtual NIC. Both physical and virtual MAC addresses follow the same 48-bit structure and include an OUI, but physical ones belong to real hardware while virtual ones are assigned digitally and may come from reserved virtualization ranges. A virtual NIC still needs a MAC address because Layer 2 networking depends on MAC addresses to deliver frames, and the VM must behave like a real device on the network.

MAC Addresses in the OSI Model

MAC addresses operate at OSI Layer 2, where ethernet handles local delivery of frames. They never leave the local network because routers strip off the Layer 2 frame and only forward the Layer 3 packet to the next network. When a router sends the packet out another interface, it creates a new ethernet frame with new source and destination MAC addresses appropriate for the next hop.

Understanding Logical Addressing

IPv4 and IPv6

Physical vs. Logical Address Comparison**

Physical Address (MAC Address)

• Set by the manufacturer and stored in the NIC hardware
• Stays the same no matter what network the device joins
• Used for communication inside a local network (Layer 2)
• Written in hexadecimal
• Identifies the specific hardware of the device

Logical Address (IP Address)

• Assigned by a network and can change depending on where the device connects
• Used for communication between networks and across the internet (Layer 3)
• Written in IPv4 or IPv6 format
• Helps routers send data to the correct destination
• Identifies the location of a device on a network

Both

• Used to identify devices on a network
• Work together so data can move locally and globally
• Are required for sending and receiving packets

IPv4 vs. IPv6

IPv4 IPv4 is the older version of the Internet Protocol that uses 32-bit addresses—numbers. It allows about 4 billion unique addresses, which isn’t enough for the number of devices.

IPv6 IPv6 is the newer version of the Internet Protocol that uses 128-bit addresses—longer, hex-based numbers. It was created because of the limited IPv4 addresses. IPv6 includes improvements such as better routing efficiency and built-in security features.

Automatic IPv6 link-local Address

An IPv6 link-local address is a special type of IPv6 address that is only valid on the local network segment and is used for communication between devices on the same link. It always begins with fe80:: because that prefix is reserved by the IPv6 standard specifically for link-local addressing. These addresses support essential local functions such as neighbor discovery, router discovery, and local device-to-device communication. They do not require DHCP or any outside configuration because they are generated automatically using the device’s interface information and built-in IPv6 rules. Every IPv6 device creates a link-local address by default so it can participate in local network operations even if no router, DHCP server, or global IPv6 network is available.

IPv6 and the Future of Networking

IPv4 is no longer sufficient because its 32-bit address space can only support about 4.3 billion unique addresses, which is far too limited for today’s number of devices. IPv6 solves this exhaustion by using 128-bit addresses, providing an almost unlimited supply that can support global growth for decades. Beyond just more addresses, IPv6 introduces improvements like more efficient routing, built-in security features, and better support for mobile devices. However, since the entire internet still relies heavily on IPv4, networks must support both IPv4 and IPv6 during the transition so older systems remain reachable while newer systems can take advantage of IPv6. This dual-stack approach ensures compatibility and smooth communication across all networks.

IPv4 vs IPv6 Comparison Table

Feature	IPv4 (in my own words)	IPv6 (in my own words)
Address length	Uses 32 bits, which is enough for a few billion unique addresses.	Uses 128 bits, giving an extremely large number of possible addresses.
Notation	Written as four decimal numbers separated by dots (like 192.168.1.10).	Written in hexadecimal with groups separated by colons (like fe80::1).
Approximate capacity	Can handle around 4.3 billion total addresses.	Has so many addresses that we basically won’t run out.
Example	Example: 10.0.0.25 or your VM’s IPv4 address.	Example: fe80::xxxx:xxxx:xxxx:xxxx or a global IPv6 address.
Where it is used	Common on home networks, Wi-Fi routers, and older systems.	Used on newer devices, link-local communication, and modern internet services.

Logical Addressing

IP addresses are needed in addition to MAC addresses because MACs only identify devices on a local network, while IP addresses provide a global location that allows devices to communicate across multiple networks. IP addresses work like a mailing address, letting data know where to go beyond the local LAN so it can reach the correct device anywhere in the world. Routers use the network portion of an IP address to determine the best path to forward packets toward their destination, effectively connecting different networks together. Without IP addresses, a computer could only talk to devices directly on the same local network, and internet communication would be impossible. For example, when browsing a website, the computer uses its IP address so routers can send requests and responses back and forth between my home network and the website’s server, even though they are thousands of miles apart. This combination of MAC and IP addresses ensures that data reaches the correct device both locally and globally. Overall, IP addressing is essential for scalable, worldwide communication.

Dynamic vs. Static Addressing & When to Use Each

Addressing: Physical and Logical

Ubuntu VM

IPv4 and IPv6 addresses currently assigned to VM #1 using ip addr show. Shows whether the IP is dynamic or static.

VM #1 Netplan configuration file showing DHCP settings (dhcp4: / dhcp6:)

Linux

IPv4 and IPv6 addresses currently assigned to VM #2 using ip addr show. Shows whether the IP is dynamic or static.

VM #2 network configuration showing the method used (Netplan, NetworkManager, or interfaces) and the DHCP status

• Putting sudo after the first command - result: ran successfully

The VM uses Network Manager and Netplan.

Static vs. Dynamic Addressing

Dynamic addressing is a method where a device automatically receives an IP address from a DHCP server when it connects to a network. These addresses are lease-based, meaning they are temporary and can change over time, which makes this method highly scalable and efficient for networks with many devices that frequently join or leave, such as laptops, smartphones, and guest devices. In contrast, static addressing involves manually assigning an IP address to a device, which remains the same unless it is manually changed. This provides predictability and reliability, which is essential for critical devices like servers, printers, routers, and security cameras that need to be consistently reachable. Networks need both methods because dynamic addressing simplifies management for everyday devices, while static addressing ensures important devices remain accessible at a fixed location. Overall, dynamic addressing is best for end-user devices that require flexibility, and static addressing is ideal for devices that provide essential services or require secure, consistent access.

Scenario Analysis Table

Device	Static or Dynamic?	Justification (2 sentences)
School web server	STATIC	The web server must always be reachable by students and staff, so a consistent IP address is required. Changing its address could break access to hosted websites and services.
Classroom printer	STATIC	All users need to reliably find the printer on the network, so a fixed IP ensures it can always be located. This prevents printing errors caused by changing addresses.
Student laptops	DYNAMIC	Laptops frequently join and leave the network, so dynamic addressing allows them to receive IPs automatically without manual setup. This makes network management easier for administrators.
Security cameras	STATIC	Cameras need a permanent IP so monitoring systems and security software can consistently access them. Changing addresses could disrupt video feeds or remote management.
Teacher workstation	DYNAMIC	If the workstation moves between classrooms or is not providing network services for others, dynamic addressing allows flexible network access. It simplifies setup and reduces manual configuration.

Comparison of VMs

VM #1 uses Netplan for its network configuration, with dhcp4: true indicating that its IPv4 address is assigned dynamically, and a similar line may exist for IPv6 if it is also dynamic. VM #2 also uses Netplan but may integrate with NetworkManager, which is common in desktop-oriented Linux systems, allowing for flexible, user-friendly network management. Both VMs use similar syntax for DHCP configuration, but file names, additional settings, or the presence of NetworkManager can differ, reflecting differences in system setup and intended use. While VM #1 relies solely on Netplan, VM #2’s combination with NetworkManager shows how some systems prioritize dynamic connections for easier management. These differences occur because Linux distributions vary in how they handle networking based on whether the system is server-focused, desktop-focused, or intended for multiple users. Overall, the IP addresses on both VMs are dynamically assigned, but the methods and tools used to manage them differ, demonstrating how Linux networking can be configured in multiple ways depending on the environment and purpose.

Configuring and Verifying IP Addresses on a Linux VM

• Edited YAML File

• shows the static IP assigned to your interface

• shows the default route pointing to the gateway

• verifies external connectivity

Explination

Physical addressing uses MAC addresses, which are unique identifiers burned into a device’s network interface card. These addresses allow devices to recognize each other on the local network, but they cannot route traffic beyond that network. IP addresses provide logical addressing, allowing devices to communicate across multiple networks, such as the internet. While DHCP can automatically assign IP addresses (dynamic IPs), static IPs are manually set and remain constant, which is useful for servers, printers, or other devices that need a consistent network location. IP addresses are necessary in addition to MAC addresses because routers use IPs to determine where to send data across different networks. Without IPs, devices could only communicate locally and not reach external networks. Using a static IP ensures predictable network behavior, whereas dynamic IPs make network management easier for devices that do not require fixed addresses.

Reflection

The most challenging part of the IP configuration was getting the YAML indentation exactly correct, because even a single extra space or a tab would cause Netplan to fail. YAML is extremely syntax-sensitive, and small mistakes can prevent the network from working, which reinforced the importance of careful editing. IP settings must be precise for routing and connectivity, since the gateway and DNS must be correct for the system to communicate properly. When the configuration didn’t work at first, some troubleshooting by checking for typos, fixing indentation, and verifying the interface name helped successfully apply the static IP.