Lessons

What is Graph Query Language (GQL)?

Lesson

Graph Query Language is a standardized syntax for managing, querying and manipulating property graphs.

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WAN Technologies - HDLC, PPP, Frame Relay and Ethernet

Lesson

Wide Area Networks may use one of several layer 2 technologies to encapsulate data as it cross a service providers network between a customer’s sites.

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What is a computer network?

Lesson

An overview of what might constitute a computer network.

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Block Ciphers

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Block ciphers operate on blocks of data of a particular size.

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Types of Memory in Computer Architecture

Lesson

There are different types of memory available for storing data in a computer. Learn about what they are and what they are used for.

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What is a LAN?

Lesson

Learn about devices found on local-area networks and how they are connected.

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How does IPv4 work?

Lesson

IPv4 has been at the heart of the TCP/IP stack since it's inception. It is slowly being replaced by IPv6.

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How to use the man pages on Linux

Lesson

Getting help on Linux with the 'man pages' and where else to look.

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CDP and LLDP

Lesson

CDP and LLDP are similar layer two protocols for discovering information about neighboring devices.

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Telnet vs SSH

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Telnet and SSH are both protocols used for interacting with remote devices. Learn about the differences and the details.

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The OSI 7 Layer Reference Model

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A conceptual network model which is often used as a reference but not implemented practically.

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Regex Subexpressions

Lesson

Subexpressions let us split a regular expression up into smaller groups which we can use for many things!

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Stream Ciphers

Lesson

Stream ciphers are encryption algorithms which encrypt data one bit at a time.

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Network Proxies: The Different Types Explained

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Network proxies are seen in many networks and used by enterprises, service providers and individuals. Three of the primary uses for proxies are forward proxies (seen in enterprise networks), reverse proxies (which deliver web services) and privacy/anonymisation focused proxies.

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What are Regular Expressions?

Lesson

Regular expressions are patterns specified with a defined syntax which are used to search text for specific sequences of characters with many practical applications.

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Introduction to IPv4 Routing

Lesson

IP routing is at the heart of the internet. It enables us to get packets from A to B across the globe.

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A Beginner's Guide to Binary

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Binary is just another way of counting. Instead of using base-10 (decimal), we use base-2 where each place value is a bit.

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Network Sockets and Ports

Lesson

Network sockets are software structures that represent the endpoints of a network connection. A pair of sockets fully specify a network connection, and these connections enable communication in both directions. There are three main types of network socket: datagram, stream and raw.

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Summary of the TCP/IP Model

Lesson

An overview of TCP/IP, or the Internet Protocol Suite, which underpins all modern computer networks.

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Same layer and adjacent layer interactions

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Learn about interactions at the same layer and between adjacent layers, including encapsulation and protocol data units (PDUs).

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Ethernet at the Data-Link Layer

Lesson

At the data-link layer, Ethernet provides an interface between the physical layer and the higher network layers. It also specifies MAC address formats.

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Linux directory commands for beginners

Lesson

All the basics you need to learn for moving around the filesystem on the command line.

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Basic Regex Character Matching

Lesson

Learn how to match standard character classes with regular expressions.

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TCP: The Transmission Control Protocol

Lesson

TCP is a connection-oriented protocol used at the transport layer to support protocols such as HTTP.

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Ping and ICMP

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Ping is a useful tool for checking network connectivity using the Internet Control Message Protocol (ICMP).

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DNS: The Domain Name System

Lesson

DNS is used to resolve friendly names (e.g. www.example.com) to IP addresses (e.g. 1.2.3.4), making it vital to our use of the internet.

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What is a WAN?

Lesson

Wide area networks enable data to be transferred across large geographic distances.

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Netcat Field Guide

Lesson

Netcat (nc) is a simple but versatile utility for TCP and UDP communication.

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ARP: The Address Resolution Protocol

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ARP helps us match IP addresses to hardware (MAC) addresses.

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Firewalls in Computer Networking

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Firewalls play an important part in protecting modern computer networks.

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Virtual LANs (VLANs)

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VLANs are used in modern computer networks to support logically separate LANs on a single device.

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VLSM Subnetting in Networks

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VLSM helps make more efficient use of available IP address space.

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What do network switches do?

Lesson

Learn what network switches do in a TCP/IP network and how they work.

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How does HTTP work?

Lesson

HTTP is used by web browsers and many other applications to retrieve websites and much more.

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RIP and RIPv2, The Routing Information Protocol

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RIP was one of the first routing protocols to be implemented. RIPv2 later added a number of improvements.

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Custom Sets in Regular Expressions

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Learn to define your own sets of characters to be matched with a regular expression.

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Hashes and Computer Security

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A cryptographic hash is a one way function for which it is very difficult to get back the input when given just the output.

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Access Control Lists for Beginners

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Access control lists (ACLs) provide a simple but effective layer of security in modern networks.

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The Complete Guide to IPv4 Subnetting

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Learn how to design subnets and calculate the number of hosts on each.

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Matching a Certain Number of Repetitions with Regex

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Use regular expressions to match on a certain number (or range) of repetions of a certain character or class of characters.

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The Linux Terminal and Shell

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Learn about the Linux terminal and why it's so useful.

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Collision and Broadcast Domains

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Collision and broadcast domains are important properties of an Ethernet network.

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Routing Between VLANs

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To let devices on one VLAN talk to the devices on another, we need to be able to route between them.

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Ethernet at the Physical Layer

Lesson

Ethernet sits at the link layer in TCP/IP but what does it define about the OSI physical layer?

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UDP: User Datagram Protocol

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UDP is a simple transport layer protocol.

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How does traceroute work?

Lesson

The traceroute command is useful tool installed on hosts and network devices for troubleshooting networking issues by tracing the route of a packet across a network.

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NAT: Network Address Translation

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NAT is the mapping of one address to another. It is a useful tool for conserving IP address space.

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Regex Anchors

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We can specify where we want to match with a regular expression using word and string boundaries.

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Using tcpdump: Options, Filters and Examples

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'tcpdump' is a command-line tool available for UNIX based systems (including macOS and Linux) that captures network traffic and displays it on screen or saves it to a file. It is a simple but powerful tool for troubleshooting network problems, understanding protocols, investigating suspicious network activity, and much more.

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