Network hardware Revision Notes

A Network Interface Card (NIC) is a hardware component installed in a computer or device that allows it to connect to a network. It acts as the interface between the device and the physical network medium, such as Ethernet cables or wireless signals.

Without a NIC, a computer cannot send or receive data over a network, making it essential for network communication. NICs can be integrated into the motherboard or added as separate expansion cards.

For example, a desktop computer connected to a home router via an Ethernet cable uses a NIC to transmit and receive data packets.

• NIC provides physical and data link layer connectivity.
• It can be wired (Ethernet) or wireless (Wi-Fi).
• Enables communication with other devices on the network.

Each NIC is assigned a unique Media Access Control (MAC) address. This address is a hardware identifier embedded by the manufacturer and is usually expressed as six pairs of hexadecimal digits (e.g., 00:1A:2B:3C:4D:5E).

The MAC address operates at the data link layer and is used to identify devices within the same local network. It ensures that data frames are delivered to the correct hardware destination.

For instance, when a data packet arrives at a router, the MAC address helps direct it to the intended device on the local network.

• MAC address is unique to each NIC worldwide.
• It is a 48-bit address expressed in hexadecimal.
• Used for device identification on local networks.

When a computer sends data over a network, the NIC formats the data into frames and attaches the MAC address as the source address. The destination MAC address specifies which device should receive the data.

Network devices use MAC addresses to filter and forward data correctly. This process is fundamental in Ethernet networks where devices communicate directly using MAC addresses.

For example, if Computer A wants to send a file to Computer B on the same network, Computer A’s NIC uses Computer B’s MAC address to ensure the data reaches the correct device.

• NIC uses MAC addresses to send and receive data frames.
• MAC addresses enable accurate delivery within local networks.
• NIC hardware handles addressing and data transmission tasks.

A laptop connecting to a Wi-Fi network uses a wireless NIC to communicate with the wireless access point. The NIC’s MAC address identifies the laptop on the wireless network.

A server connected via Ethernet cable uses a wired NIC with a unique MAC address to communicate with other servers and clients in a data centre.

In both cases, the NIC and its MAC address are essential for establishing and maintaining network connections.

• Wireless NICs connect to Wi-Fi networks.
• Wired NICs connect via Ethernet cables.
• MAC addresses remain constant regardless of network type.

A Network Interface Card is indispensable for any device to participate in a network. It provides the physical connection and handles data transmission.

The MAC address assigned to each NIC uniquely identifies the device on the local network, enabling proper routing of data frames.

Understanding NICs and MAC addresses is fundamental for grasping how devices communicate within networks and how data is directed to the correct hardware.

• NIC enables network connectivity at hardware level.
• MAC address uniquely identifies devices locally.
• Together, they ensure reliable data communication.

A Media Access Control (MAC) address is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. It operates at the data link layer (Layer 2) of the OSI model and is essential for devices to communicate on local networks such as Ethernet or Wi-Fi.

Unlike IP addresses, which can change depending on the network, a MAC address is fixed to the hardware and does not change. This permanent address allows devices to be uniquely identified on a local network, ensuring that data packets reach the correct destination device.

• MAC addresses identify devices on the physical network segment.
• They operate at the data link layer (Layer 2) of the OSI model.
• They are unique and fixed to the network interface hardware.

A MAC address consists of 48 bits, usually displayed as 12 hexadecimal digits grouped into six pairs separated by colons or hyphens (e.g., 00:1A:2B:3C:4D:5E). Each hexadecimal digit represents 4 bits, so 12 digits × 4 bits = 48 bits total.

The address is divided into two main parts: the first 24 bits (the first six hexadecimal digits) represent the Organizationally Unique Identifier (OUI), which identifies the manufacturer of the network device. The remaining 24 bits (the last six hexadecimal digits) are a unique serial number assigned by the manufacturer to that specific device.

For example, if a MAC address is 3C:5A:B4:12:34:56, the '3C:5A:B4' part identifies the manufacturer, and '12:34:56' is the unique device number.

• MAC address length: 48 bits (6 bytes).
• First 24 bits = manufacturer code (OUI).
• Last 24 bits = unique serial number assigned by manufacturer.
• Expressed in hexadecimal format for compactness and readability.

MAC addresses are assigned by device manufacturers during production. This ensures that each network interface card (NIC) has a globally unique address, preventing address conflicts on networks.

The use of hexadecimal format is practical because it condenses the binary 48-bit address into a shorter, human-readable form. Each hexadecimal digit corresponds to four binary bits, making it easier to record and communicate MAC addresses without errors.

Manufacturers obtain their unique OUI from a central authority, which guarantees that no two manufacturers use the same prefix, maintaining global uniqueness.

• Assigned at manufacturing to guarantee uniqueness.
• Hexadecimal format condenses binary data for readability.
• Manufacturers register OUIs to avoid duplication.

When a device sends data over a local network, it uses the MAC address to specify the destination device. Network switches use MAC addresses to forward data frames only to the intended recipient, improving network efficiency.

For example, if a computer wants to send data to a printer on the same network, it uses the printer’s MAC address to ensure the data reaches the correct device. This is crucial because IP addresses can change or be shared, but MAC addresses uniquely identify hardware interfaces.

MAC addresses are also used in protocols like ARP (Address Resolution Protocol) to map IP addresses to MAC addresses, enabling communication between devices on the same local network.

• Used to direct data frames to the correct device on a local network.
• Essential for switches to forward data efficiently.
• Supports protocols like ARP for IP-to-MAC address mapping.

Understanding MAC addresses helps in network configuration and troubleshooting. For instance, network administrators can filter or allow devices based on their MAC addresses for security purposes.

If a device cannot connect to a network, checking its MAC address can help verify if it is correctly recognised by the network hardware or if MAC filtering is blocking it.

Tools like 'ipconfig /all' on Windows or 'ifconfig' on Linux display the MAC address of network interfaces, aiding diagnostics.

• MAC addresses can be used for network access control.
• Checking MAC addresses assists in troubleshooting connectivity issues.
• Network tools display MAC addresses for device identification.

An Internet Protocol (IP) address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It serves two main purposes: to identify the device (host) on the network and to provide its location within the network structure, enabling data to be routed correctly between devices.

Every device that accesses the internet or a local network must have an IP address to send and receive data packets. Without an IP address, a device cannot participate in network communication.

For example, when you visit a website, your device’s IP address is used to send the request to the server and to receive the response back.

• Uniquely identifies a device on a network.
• Provides location information for routing data.
• Essential for network communication.

IP addresses can be assigned in two main ways: static or dynamic. A static IP address is manually assigned to a device and does not change over time. This is useful for devices that need a consistent address, such as servers or network printers.

In contrast, a dynamic IP address is assigned automatically by a Dynamic Host Configuration Protocol (DHCP) server each time a device connects to the network. Dynamic addresses can change with each connection or after a certain lease period expires. This method is common for most home users and mobile devices, as it conserves the limited pool of available IP addresses.

For example, a home router typically assigns dynamic IP addresses to devices like smartphones and laptops, while a company’s web server might have a static IP address to ensure it is always reachable at the same address.

• Static IP addresses remain constant and are manually set.
• Dynamic IP addresses are assigned automatically and can change.
• Dynamic addressing helps manage limited IP address availability.

IPv4 (Internet Protocol version 4) is the most widely used IP addressing system. It uses a 32-bit address format, typically written as four decimal numbers separated by periods (dots), known as dotted decimal notation. Each number ranges from 0 to 255.

For example, an IPv4 address might look like 192.168.1.10. The 32 bits allow for approximately 4.3 billion unique addresses (2^32). However, due to the rapid growth of internet-connected devices, the available IPv4 addresses have become insufficient.

IPv4 addresses are divided into network and host portions, which help routers determine where to send data packets. Subnet masks are used to specify this division.

• Uses 32-bit addresses written as four decimal numbers (0-255) separated by dots.
• Supports about 4.3 billion unique addresses.
• Address format example: 192.168.1.10.

IPv6 (Internet Protocol version 6) was developed to overcome the limitations of IPv4, primarily the shortage of available addresses. It uses a 128-bit address format, allowing for a vastly larger number of unique addresses (approximately 3.4×10^38).

IPv6 addresses are written as eight groups of four hexadecimal digits separated by colons, for example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334. Leading zeros in each group can be omitted, and consecutive groups of zeros can be replaced by a double colon (::) once per address to simplify notation.

The large address space of IPv6 supports the growing number of devices connected to the internet and enables improved routing and security features.

• Uses 128-bit addresses written as eight groups of four hexadecimal digits separated by colons.
• Supports an extremely large number of unique addresses.
• Address format example: 2001:0db8:85a3::8a2e:0370:7334.

IP addresses are fundamental for identifying devices and enabling communication on networks. Static IP addresses provide fixed identification, useful for servers and devices requiring consistent access. Dynamic IP addresses offer flexibility and efficient address management for most users.

IPv4 remains the dominant addressing system but is limited in capacity. IPv6 addresses this limitation with a much larger address space and enhanced features, ensuring the continued growth and scalability of the internet.

• IP addresses identify devices and enable network communication.
• Static addresses are fixed; dynamic addresses change over time.
• IPv4 uses 32-bit addresses; IPv6 uses 128-bit addresses for more devices.

A router is a specialised networking device that manages data traffic between different networks. Unlike simpler devices such as switches or hubs, a router can determine the best path for data packets to travel, ensuring efficient and accurate delivery to their intended destinations. Routers are essential components in both home and enterprise networks, enabling communication within local networks and with external networks like the internet.

• Routers operate at the network layer (Layer 3) of the OSI model.
• They connect multiple networks together, such as a home network and the internet.
• Routers use routing tables and protocols to decide where to send data packets.

When a device sends data over a network, the data is broken into packets. Each packet contains the destination IP address. The router examines this address and uses its routing table to forward the packet along the best path towards that destination. This process is called routing.

For example, if a computer in a home network requests a webpage, the router directs the outgoing request to the internet and routes the incoming webpage data back to the correct device within the local network.

• Routers read destination IP addresses in data packets.
• They use routing tables to find the optimal path.
• Routing ensures data reaches the correct device or network.

Routers often include a Dynamic Host Configuration Protocol (DHCP) server that automatically assigns IP addresses to devices on the local network. This process simplifies network management by ensuring each device has a unique IP address without manual configuration.

For instance, when a smartphone connects to a home Wi-Fi network, the router assigns it an IP address dynamically, allowing it to communicate with other devices and access the internet.

• Routers can act as DHCP servers.
• They assign unique IP addresses to devices on the local network.
• This prevents IP address conflicts and eases network setup.

A key function of a router is to connect a local area network (LAN) to a wide area network (WAN), such as the internet. The router manages traffic between the LAN and the internet, often performing Network Address Translation (NAT) to allow multiple devices to share a single public IP address.

For example, a home router connects all household devices to the internet through one ISP-provided IP address, enabling simultaneous internet access for multiple devices.

• Routers link local networks to external networks like the internet.
• They manage data flow between LAN and WAN.
• Network Address Translation allows multiple devices to share one public IP address.

In summary, routers direct data packets to their destinations, assign IP addresses within local networks, and connect these networks to the internet. Consider a small office network: the router assigns IP addresses to all office computers, directs internal data traffic, and connects the office network to the internet for email and web access.

This integration of functions makes routers indispensable for modern networking, ensuring efficient communication both inside and outside the local network.

• Routers combine routing, IP address assignment, and internet connectivity.
• They enable seamless communication within and beyond local networks.
• Example: Office router managing devices and internet access simultaneously.