IT Support, Networking and Infrastructure
Networking fundamentals
Every other part of IT assumes the network works, which is why a gap here surfaces everywhere else. The fundamentals are a short list of ideas: how traffic is addressed, how names become addresses, how a device obtains its settings, and a shared model for saying where a fault sits. Vendor-neutral and Cisco exams alike open with exactly this, and nothing further up the silo makes sense without it.
Why this topic exists: The OSI and TCP/IP models, addressing, subnetting, DHCP and DNS are the first domains of Network+ (Networking concepts 23 %) and CCNA (Network Fundamentals 20 %).
Networking fundamentals explain how one device reaches another. A laptop joins a network and asks for its settings through DHCP; it is handed an IP address, a mask that says which neighbours are local, a gateway for everything that is not, and a resolver for DNS. When the user types a name, DNS turns it into an address, TCP/IP carries the request out, switches move it inside the building and routers move it between networks. A support technician, a Linux administrator and a network engineer all spend their days somewhere along that chain, and all of them fix faults by finding the link that broke.
The OSI model and the TCP/IP model are two vocabularies for describing the chain. Neither is software you can install. They are conventions for naming where a problem lives, so that 'the cable is fine but the machine never got an address' becomes a precise statement rather than a hunch, and so that two engineers on a call mean the same thing when one of them says layer three.
What the blueprints put first
| Idea | What you must be able to do | Where Network+ and the CCNA test it |
|---|---|---|
| Reference models | Place a symptom at a layer and name the devices working there | Networking concepts; Network Fundamentals |
| IPv4 and IPv6 addressing | Read an address, tell private from public, spot an address a device assigned itself | Networking concepts; Network Fundamentals |
| Subnetting | Split a block by prefix length and state how many hosts each piece holds | Networking concepts; Network Fundamentals |
| Ports and protocols | Match common services to their port and transport | Networking concepts; Network Fundamentals |
| DHCP and DNS | Explain the lease exchange and the lookup, and tell a naming fault from a connectivity fault | Network operations; IP Services |
Most of these rows come down to one skill: reading the output of a handful of commands. The address a machine holds, its gateway, the resolver it asks and the path a packet takes can all be displayed in seconds on Windows, macOS or Linux, and an engineer who looks before guessing settles most faults at this level without touching a configuration. The exams test the same instinct through scenarios that describe symptoms and ask where the fault sits, and they reward the candidate who knows which piece of evidence would decide it.
Where beginners go wrong
Network+ makes these ideas its opening domain, and the CCNA's Network Fundamentals domain covers similar ground with more attention to how Cisco equipment presents it. Both then move on fast, so a candidate who rushes the basics to reach the interesting material finds that material unreadable. Subnetting is where this shows first. It is arithmetic in powers of two, and anyone who tries to learn it by rote from a chart stalls on every later question about routes and VLANs; three worked examples done by hand teach more than a week of flashcards.
The other habit to break is troubleshooting from the top down, reinstalling an application on a machine that never had an address. Work upwards instead: link light, address, gateway, name resolution, then the service. Once that order is automatic, the next topics are routing and switching, where traffic between networks is decided, and wireless networking. Cisco's free Networking Basics course lets you test your interest before you pay for Network+ or the CCNA. Deciding what traffic should be allowed at all is a separate discipline, covered under network security.
Within this topic
- Routing, switching and Cisco networksVLANs, spanning tree, static and dynamic routing: CCNA's Network Access (20 %) and IP Connectivity (25 %) domains, with NAT in IP Services, and the daily work of a network engineer.
- Wireless networkingWi-Fi standards, radio, security modes and site design are their own competence in Network+ and CCNA (Network Access) and the commonest support ticket in small offices.
- IT fundamentalsWhat computers, networks, operating systems and data are for, before fixing any of them: the scope of Tech+ and of the first weeks of every support course (SFIA Delivery and operation; A+ Core 1).
- Hardware, mobile devices and troubleshootingComponents, peripherals, mobile devices and the troubleshooting method are the largest part of A+ Core 1 (Hardware 25 %, Hardware and Network Troubleshooting 28 %, Mobile Devices 13 %, read 2026-09-26).
- Operating systems: Windows, macOS, LinuxInstalling, configuring and securing desktop operating systems is A+ Core 2's largest domain (Operating Systems 28 %) and the daily ground of support work.
- Linux administrationThe command line, package management, filesystems, users, services, scripting and networking as LPIC-1 objectives v5.0 lay them out (topics 101–110); Linux+ and RHCSA test the same ground.
- Windows Server and Active DirectoryDomains, group policy, file and print, identity for the desktop estate: the server side of most business IT (SFIA System software administration; Microsoft's Windows Server hybrid administrator track).
- IT support and the service deskTickets, incidents, requests, remote support and the operational procedures of A+ Core 2 (21 %): the job most people enter IT through (Google IT Support; ITIL's service desk and incident practices).
- IT service management (ITIL)The practices that run IT as a service: incident, problem, change enablement, service level, continual improvement (ITIL's practice model, Version 5 since February 2026 with ITIL 4 in parallel; ITIL Foundation; ServiceNow CSA).
- Virtualisation and server infrastructureHypervisors, virtual machines and server hardware sit between the desktop and the cloud (A+ Core 1 Virtualization and Cloud Computing 11 %; SFIA Infrastructure operations; VMware and Server+).
- Scripting and automation for administratorsPowerShell, Bash and Python are how administrators stop doing the same thing twice (LPIC-1 topic 105; CCNA Automation and Programmability 10 %; SFIA System software administration).
Concepts to know
Glossary entries with the reason each one matters here.
- OSI Model
The layered model used to reason about where a packet stopped.
- TCP/IP
The protocol suite the internet runs on.
- IP Addressing
Addresses, masks and the difference between public and private.
- Subnetting
The arithmetic every network exam tests.
- DHCP
How hosts get their addresses.
- DNS
How names become addresses.
Certifications that test it
Vendor exams and free certificates; facts, cost and the preparation path are on each page, and the certifications hub has them all.
- CompTIA · N10-009CompTIA Network+The vendor-neutral networking exam.
- Cisco · 200-301Cisco Certified Network Associate (CCNA)Cisco's associate exam starts with network fundamentals.
- Cisco · Online exam, not proctored · freeNetworking BasicsA free 22-hour start with a Credly badge.
- CompTIA · 220-1201 + 220-1202CompTIA A+Networking is a quarter of Core 1.
Tools of the trade
- Wireshark
Seeing the packets.
- Cisco Packet Tracer
A first network, built and broken without hardware.
Frequently asked
- Do I need to memorise all seven OSI layers?
- For the exams, yes, along with what typically works at each one. In practice you will mostly use layers one to four and the application at the top, and the value lies in describing a fault precisely rather than in reciting the list.
- Should I learn IPv6 now or later?
- Now, alongside IPv4. Mobile networks and cloud providers already run it widely, both Network+ and the CCNA examine it, and learning it as an afterthought leaves you treating a normal part of the network as an exotic one.
- Is Network+ or the CCNA better for the fundamentals?
- Both cover them well. Network+ stays neutral and spends more time on operations and troubleshooting; the CCNA covers the same basics and then goes deeper into configuring Cisco devices. Choose by where you want to go next rather than by which explains subnetting better.
Courses in the directory
112 courses are filed here; the top 6 by our ranking, details and the provider link on each course page.
Data Networking 101
Udemy
Last reviewed 26 September 2026 · Getting Digital