6.07 Install and configure basic wired and wireless small office and home office (SOHO) networks
Introduction
Imagine a busy postal system where packages (data) need to be delivered to the right people (devices) efficiently and securely. Just as a postal system relies on a set of rules to deliver mail, computers and networks depend on protocols to communicate. Protocols act like traffic signals, guiding data through the Internet and ensuring it reaches the right destination.
In this lesson, you’ll explore how different layers of the TCP/IP model work together, handling everything from sending emails to web browsing. You’ll also learn about IPv4 addressing and how to break down and understand these addresses. Mastering these skills will help you solve networking issues, making you a resourceful problem-solver who can assist others in navigating the complexities of networks and the Internet.
What is a Protocol?
A protocol is a set of rules that allows devices on a network to share data. Several protocols can work together, forming what's called a protocol suite. Most networks today use the TCP/IP suite (Transmission Control Protocol/Internet Protocol). To understand how these protocols work, they are divided into layers. Each layer adds its own information, called a header, to the data.
Layers of the TCP/IP Model
1. Link Layer (Network Interface)
Handles the physical transmission of data on the local network.
Uses technologies like Ethernet and Wi-Fi.
Data is packaged into units called frames and identified by a device’s MAC address.
Only manages communication within a local network, not between different networks.
2. Internet Layer
Manages data addressing and routing across networks using the Internet Protocol (IP).
Devices that communicate on this layer are called end system hosts.
Routers forward data between networks.
Address Resolution Protocol (ARP) translates IP addresses into MAC addresses to deliver data.
IP provides unreliable, connectionless delivery, meaning data might be lost or delivered out of order.
3. Transport Layer
Manages multiple connections between devices.
Uses two main protocols:
Transmission Control Protocol (TCP): Ensures reliable, connection-oriented data delivery.
User Datagram Protocol (UDP): Faster but less reliable, used for time-sensitive tasks like video or voice.
4. Application Layer
Manages specific tasks like web browsing and email.
Protocols include HTTP (web), SMTP (email), and FTP (file transfer).
Each protocol uses a port to connect a client to a server.
Introduction to IPv4 Addressing
IPv4 is a key protocol in TCP/IP that handles network and device addressing, as well as moving data between networks. An IPv4 address is 32 bits long.
In its raw form, it looks like a long string of 1s and 0s, for example:
11000000101010000000000000000001.
This address can be split into four groups of 8 bits called octets:
11000000 10101000 00000000 00000001.
Since this format is hard for people to read, it’s converted into dotted decimal notation. Each octet is turned into a decimal number, separated by periods.
For example:
11000000 10101000 00000000 00000001 becomes 192.168.0.1.
In dotted decimal notation:
If all bits in an octet are 1s, the value is 255.
If all bits are 0s, the value is 0.
IPv4 addresses range from 0.0.0.0 to 255.255.255.255, but some of these addresses are reserved for special purposes.
Understanding Network Prefixes in IPv4 Addressing
An IPv4 address contains two parts:
Network ID: Identifies the network.
Host ID: Identifies a specific device (host) on that network.
These two parts are separated by a network prefix. A network prefix is a 32-bit value where a certain number of bits are set to 1.
For example, a 24-bit prefix looks like this:
11111111 11111111 11111111 00000000, which can be written as /24 in slash notation.
The prefix can also be shown as a subnet mask in dotted decimal, like 255.255.255.0.
Subnet Mask: Divides a single network into smaller subnetworks (subnets).
The prefix hides the Host ID part of the address, leaving only the Network ID visible. Where there is a 1 in the prefix, that part of the IP address is part of the Network ID.
Slash notation is used to refer to networks.
For example:
192.168.0.0/24 refers to an entire network.
192.168.0.1/255.255.255.0 refers to a specific device on that network.
Analogy:
Think of an IPv4 address like a mailing address on a large apartment complex. The network ID is like the apartment building number, which is the same for all residents in that building. The host ID is like the apartment number for each individual resident.
Now, the network prefix is like the building’s layout map, showing which part of the address refers to the building (network) and which part refers to the individual apartment (host). If you have a layout map that only shows the building number and hides the apartment numbers, it’s like a subnet mask hiding the host ID and only revealing the network ID.
In this way, the network prefix helps route the data to the right building (network), and once inside, it’s directed to the correct apartment (host).
What is IPv4 Forwarding?
When a device (host) wants to send data using IPv4, it checks the source IP address (the sender’s IP) and the destination IP address (the receiver’s IP) against the subnet mask of the sender. The subnet mask helps determine if both devices are on the same network.
Here’s how it works:
Same Network
If the network parts of the source and destination IP addresses match after applying the subnet mask, it means the destination is on the same network.
The host will try to deliver the packet directly, without needing to send it to another network.
Example:
Source IP: 192.168.0.100
Destination IP: 192.168.0.200
Subnet Mask: 255.255.255.0
In this case, the network ID for both IP addresses is 192.168.0.0, meaning they are on the same network. The host will use the Address Resolution Protocol (ARP) to find the MAC address of the destination and deliver the packet locally.
Different Network
If the network parts of the source and destination IP addresses do not match, the host knows the destination is on a different network.
The packet will need to be sent to a router for delivery to the correct network.
Example:
Source IP: 192.168.0.100
Destination IP: 192.168.1.100
Subnet Mask: 255.255.255.0
Here, the source and destination have different network IDs (192.168.0.0 vs. 192.168.1.0), so the host forwards the packet to a router to be sent to the correct network.
Default Gateway
Most hosts are set up with a default gateway, which is the IP address of the router that can forward packets to other networks.
The default gateway must be on the same network as the host.
For example, if the host's IP is 192.168.0.100, the default gateway could be 192.168.0.1.
Analogy:
Imagine you’re sending a letter. First, you check if the recipient lives in the same neighborhood. If they do, you can deliver the letter directly to their house, much like how a host sends data directly when the source and destination are on the same network.
However, if the recipient lives in a different neighborhood, you take the letter to the local post office, which then routes it to the correct neighborhood.
Similarly, when the source and destination are on different networks, the data is sent to a router (the “post office”), which forwards it to the correct network. The default gateway is like your closest post office—always ready to forward your letter if it needs to go further than your neighborhood.
Understanding Public and Private IP Addressing
To connect to the Internet, devices need a public IP address assigned by an ISP (Internet Service Provider). Since public IPv4 addresses are limited, many companies can't get enough for all their devices, leading to the use of private addresses.
Reserved Private IP Address Ranges
Certain IP address ranges are reserved for use within private networks and are not allowed on the public Internet. These RFC 1918 addresses are meant for local communication within LANs.
The three main private IP address ranges are:
Class A: 10.0.0.0 to 10.255.255.255
Class B: 172.16.0.0 to 172.31.255.255
Class C: 192.168.0.0 to 192.168.255.255
The Role of Address Classes and Subnet Masks
IPv4 addresses were initially organized into address classes (A, B, and C) to define the network portion of an address. The subnet masks aligned with these classes and did not require further customization.
Class: A
Subnet Mask (Dotted Decimal): 255.0.0.0
Network Prefix: /8
Binary Mask: 11111111 00000000 00000000 00000000
Class: B
Subnet Mask (Dotted Decimal): 255.255.0.0
Network Prefix: /16
Binary Mask: 11111111 11111111 00000000 00000000
Class: C
Subnet Mask (Dotted Decimal): 255.255.255.0
Network Prefix: /24
Binary Mask: 11111111 11111111 11111111 00000000
How Private IP Addresses Access the Internet
Devices using private IP addresses cannot access the Internet directly. Two methods allow them to do so:
Network Address Translation (NAT): A router with a public IP address translates private addresses into public ones, enabling Internet communication.
Proxy Server: A proxy server requests Internet resources on behalf of private devices and sends the results back to them.
This approach helps devices with private addresses access the Internet indirectly, solving the issue of limited public IPv4 addresses.
IPv4 Host Address Configuration
To communicate on an IPv4 network, a host needs at least an IP address and a subnet mask. However, just having these two settings isn't enough for full functionality on an enterprise network or the Internet. Additional settings are typically required for proper operation.
Static IPv4 Configuration
In a static configuration, the host's IP address and subnet mask are manually entered:
The IPv4 address is written as four decimal numbers separated by periods, like 192.168.0.100.
The subnet mask is also entered in dotted decimal format, such as 255.255.255.0. With this mask, the IP address 192.168.0.100 belongs to the 192.168.0.0 network, and .100 is the host identifier.
In some cases, the subnet mask is entered as a prefix length, like /24, instead of using dotted decimal notation.
Important note:
The first address in an IP network (e.g., 192.168.0.0 in 192.168.0.0/24) is reserved for identifying the network itself.
The last address (e.g., 192.168.0.255) is reserved for broadcasting to all hosts on the network.
Valid host addresses range from 192.168.0.1 to 192.168.0.254.
Additional Configuration Parameters
To fully utilize a network, two additional parameters are usually configured:
Default Gateway: The default gateway is the IP address of a router that directs traffic to other networks. For example, 192.168.0.1 could be the gateway for a host on the 192.168.0.0/24 network. Without a gateway, the host can only communicate within the local network.
DNS Server Addresses:
Domain Name System (DNS) servers translate domain names (like example.com) into IP addresses. A host typically needs at least one DNS server address for Internet access, and two are often provided for redundancy (primary and alternate).
Usually, the primary DNS is the same as the gateway address (e.g., 192.168.0.1), and the router forwards DNS requests to an external DNS server.
Static Versus Dynamic Host Address Configuration
Static Addressing
Static addressing requires a network administrator to manually enter configuration details (IP address, subnet mask, gateway, etc.) on each device. This can be time-consuming and prone to errors, especially in large networks, and administrators must carefully track which IP addresses are in use to avoid duplicates. If a device is moved to a different network, the IP configuration must be manually updated.
Static IP addresses are usually reserved for specific systems, such as:
Routers
Application servers
Other devices that need a fixed address for consistent communication.
Dynamic Host Configuration Protocol (DHCP)
DHCP provides a solution to the challenges of static addressing by automatically assigning:
IP addresses
Subnet masks
Default gateway
DNS server addresses
A DHCP server manages the assignment of these settings, allowing hosts to configure themselves dynamically without manual input.
Automatic Private IP Addressing (APIPA)
When a device is set to use DHCP but cannot reach a DHCP server, it uses a fallback method called Automatic Private IP Addressing (APIPA). In this case, the device assigns itself an IP address in the range 169.254.0.1 to 169.254.255.254.
APIPA allows communication with other devices using APIPA addresses on the same local network.
Devices using APIPA cannot communicate outside their local network or with devices that have valid DHCP-assigned addresses.
Other systems may refer to this as link-local addressing. Not all hosts use APIPA, and some may leave the IP address unconfigured or set it to 0.0.0.0 to indicate the IP address is unknown.
SOHO Router Configuration
A SOHO (Small Office/Home Office) router connects a private local network (LAN) to an Internet Service Provider (ISP) through two interfaces:
Public interface (connects to the ISP)
Private interface (connects to the LAN)
Each interface needs an IP address and a subnet mask. The LAN interface acts as the default gateway for devices on the local network and is also the IP address used to access the router’s management page (e.g., https://192.168.0.1 or https://192.168.1.1).
Public IP Address
The router's public interface IP address is assigned by the ISP and must be a valid public IP (e.g., 203.0.113.1). The ISP may assign this address dynamically through DHCP or offer a static IP address option, which may involve an additional cost. A public IP address:
Is not from a private range (10.x.x.x, 172.16.x.x – 172.31.x.x, or 192.168.x.x)
Does not start with 0
Is not in the range 224.x.x.x or higher (these are reserved for special use).
Configuring the SOHO Router
Connect the computer:
Plug your computer into one of the router’s RJ45 ports or connect to the router’s wireless network using the default name (found on a sticker on the router).
Ensure your computer is set to automatically obtain an IP address.
Wait for the router's DHCP server to assign your computer a valid IP address.
Access the management interface:
Open a browser and go to the router's management URL (e.g., http://192.168.0.1 or http://www.routerlogin.com).
Ensure your computer's IP address is in the same range as the router’s LAN IP if you cannot connect.
Log in using the default administrator credentials (found in the router’s documentation or printed on the router).
Immediately change the default password to a strong password (at least 12 characters).
Setup the Internet connection:
Most routers use a setup wizard to automatically configure the public IP and Internet connection.
If manual setup is required, obtain the necessary settings (e.g., public IP, DNS, etc.) from your ISP.
Monitoring and Troubleshooting
Through the router's management console, you can view:
Line status
System logs
These features are useful for troubleshooting and may be needed by your ISP to diagnose connection issues.
IPv6 Addressing
The number of available IPv4 addresses is limited, especially considering the growing number of devices connecting to the Internet. While private addressing and NAT help manage this, IPv6 (Internet Protocol version 6) was developed to eventually replace IPv4.
IPv6 uses a 128-bit address, which allows for a much larger number of unique addresses compared to the 32-bit system used by IPv4.
IPv6 Notation
IPv6 addresses are written in hexadecimal (hex) format. A single hex digit represents four binary bits. The full 128-bit IPv6 address is divided into eight groups of 16 bits, separated by colons.
Example IPv6 address:
2001:0db8:0000:0000:0abc:0000:def0:1234
To simplify, any leading zeros in each group can be ignored, and a contiguous series of zeros can be replaced by double colons (::).
Shortened version:
2001:db8::abc:0:def0:1234
IPv6 Network Prefixes
IPv6 addresses are divided into two parts:
The first 64 bits: This is the network ID.
The last 64 bits: This is the interface identifier (similar to the host ID in IPv4).
In IPv6, there is no need for a subnet mask. Instead, the network prefix is specified using prefix notation, where /nn indicates the length of the prefix.
For example, most ISPs get a /32 block and issue customers a /48 prefix. A /48 prefix allows the private network to be divided into 65,336 subnets.
Global and Link-Local Addressing
IPv6 interfaces typically have multiple addresses:
Global address: Unique and routable on the Internet, starting with a 2 or 3.
Link-local address: Used to communicate within the local network segment, starting with fe80::.
Most hosts get their global and link-local addresses automatically from the local router using a process called StateLess Address Auto Configuration (SLAAC). IPv6 does not require a manually configured default gateway. Instead, the Neighbor Discovery (ND) protocol is used, which replaces the ARP function used in IPv4.
Dual Stack
IPv6 is intended to replace IPv4, but because the transition has been slow, most systems use both IPv4 and IPv6 at the same time. This is called dual stack. A device will try to establish a connection using IPv6 first and fall back to IPv4 if the destination does not support IPv6.
Summary
You've gained a solid understanding of essential networking concepts, from how protocols like TCP/IP help devices communicate, to the structure of IPv4 and IPv6 addressing. You've also explored the difference between static and dynamic IP configurations and learned how network prefixes and subnet masks work. Understanding public and private addressing, as well as the role of routers and DHCP servers, gives you the tools to manage network connections effectively. Keep building on these concepts—you’re doing great, and this knowledge will help you confidently tackle network challenges!