Network Administrator

Welcome to the Network Administrator roadmap. It takes you from how packets move to running, securing and troubleshooting a real network. Plan 4–6 hours a week, keep a lab notebook, and follow the steps in order — later topics build on subnetting and routing.

• Know the prerequisites: basic computer literacy and comfort with a command line
• Set up a place to practice (VirtualBox, GNS3 or Packet Tracer)
• Plan your first two weeks

• CyberA4U Academy — courses

Layered models give you a shared vocabulary for where a problem lives — a cable, a MAC address, an IP route, a port or the application. Network admins use the TCP/IP model day to day and the OSI model to communicate across teams.

• Map common protocols (Ethernet, IP, TCP/UDP, DNS, HTTP) to their layers
• Explain encapsulation and decapsulation
• Use the layers to narrow down a fault

Tools & tech: Network

• RFC 1122 — Requirements for Internet Hosts (communication layers)
• Cloudflare Learning — What is the OSI model?

Switches forward frames using MAC address tables. Understanding how they learn, flood and forward explains most "it works on one port but not another" problems.

• Read the fields of an Ethernet frame
• Explain MAC learning, flooding and the forwarding table
• Recognize the purpose of Spanning Tree Protocol

Tools & tech: Network

• Cloudflare Learning — What is a LAN?

Every host needs an address and a mask. Subnetting decides how many hosts and networks you get and is the foundation for routing, firewalls and VLANs.

• Convert between binary, dotted-decimal and CIDR notation
• Calculate network, broadcast and usable host ranges
• Design an addressing plan for a small office

Tools & tech: Network

• RFC 791 — Internet Protocol (IPv4)
• RFC 4632 — Classless Inter-Domain Routing (CIDR)

IPv6 is enabled by default on most operating systems, so it is part of your network whether you plan for it or not. Learn its address types and how hosts configure themselves.

• Read and shorten IPv6 addresses
• Distinguish link-local, unique-local and global addresses
• Explain SLAAC and the role of Neighbor Discovery

Tools & tech: Network

• RFC 8200 — Internet Protocol, Version 6 (IPv6)
• RFC 4291 — IPv6 Addressing Architecture

Routers choose where packets go next using their routing table. Start with static routes, then see how dynamic protocols such as OSPF share routes automatically.

• Read a routing table and explain longest-prefix match
• Configure static and default routes
• Explain how OSPF discovers neighbors and picks the best path

Tools & tech: Network

• Cloudflare Learning — What is routing?
• RFC 2328 — OSPF Version 2

DNS turns names into addresses, and many outages are really DNS problems. Understand resolution end to end so you can find which part failed.

• Explain recursive vs authoritative servers, caching and TTL
• Know the common record types (A, AAAA, CNAME, MX, TXT, NS)
• Troubleshoot with dig or nslookup

Tools & tech: Network

• Cloudflare Learning — What is DNS?
• RFC 1034 — Domain Names: Concepts and Facilities

DHCP hands out addresses automatically, and NAT lets many private addresses share public ones. Both run on almost every office and home router.

• Describe the DHCP DORA exchange
• Configure a scope, reservations and options
• Explain source NAT and port forwarding

Tools & tech: Network

• RFC 2131 — Dynamic Host Configuration Protocol
• RFC 3022 — Traditional IP Network Address Translator (NAT)

VLANs split one physical switch into separate networks so you can isolate guests, servers and management traffic — a core security control, not just tidiness.

• Explain access vs trunk ports and 802.1Q tagging
• Route between VLANs
• Decide what should be segmented and why

Tools & tech: Network

• NIST SP 800-41 Rev. 1 — Guidelines on Firewalls and Firewall Policy

VPNs connect sites and remote users over untrusted networks. Know the main options — IPsec, WireGuard and TLS-based VPNs — and what each protects.

• Explain tunneling and encapsulation
• Compare site-to-site and remote-access VPNs
• Describe what IPsec and WireGuard provide

Tools & tech: Network

• RFC 4301 — Security Architecture for IP (IPsec)
• WireGuard — Official documentation

Wi-Fi is usually the network users touch most. Channels, bands and security modes affect both performance and safety.

• Compare the 2.4 GHz, 5 GHz and 6 GHz bands
• Choose channels to reduce interference
• Know the difference between WPA2 and WPA3, personal and enterprise modes

Tools & tech: Network

Learn it on CyberA4U:Module 18: Wireless Network Attack Techniques

• NIST SP 800-153 — Guidelines for Securing WLANs

Packet capture shows what is really happening on the wire. It is the most reliable way to settle "is it the network?" arguments.

• Capture on the right interface
• Use capture and display filters
• Follow a TCP stream and spot retransmissions or resets

Tools & tech: Network

• Wireshark User's Guide
• Wireshark Wiki — Sample captures

A firewall is only as good as its rule set. Good policy starts from "deny by default", is documented, and is reviewed regularly.

• Write least-privilege rules for common services
• Order rules correctly
• Plan logging and periodic rule review

Tools & tech: Network

• NIST SP 800-41 Rev. 1 — Guidelines on Firewalls and Firewall Policy

Load balancers spread traffic across servers for capacity and availability. You will meet them in front of every serious web application.

• Compare layer-4 and layer-7 load balancing
• Explain round-robin, least-connections and health checks
• Understand session persistence

Tools & tech: Network

• Cloudflare Learning — What is load balancing?
• NGINX docs — Using nginx as HTTP load balancer

A repeatable method beats guessing. Work from the physical layer up, change one thing at a time, and write down what you tested.

• Apply a layered troubleshooting method
• Use ping, tracepath, ip, ss and dig effectively
• Document the root cause and the fix

Tools & tech: Network

• Linux man page — ping(8)
• Linux man page — tracepath(8)

Zero trust removes implicit trust based on network location: every request is authenticated and authorized. It changes how you think about VPNs and internal segments.

• State the core zero trust principles from NIST SP 800-207
• Explain micro-segmentation and identity-aware access
• Identify first steps for a small network

Tools & tech: Network

• NIST SP 800-207 — Zero Trust Architecture
• CISA — Zero Trust Maturity Model

Monitoring tells you about problems before users do and gives you the history to find root causes.

• Choose metrics that matter: availability, latency, errors and bandwidth
• Understand SNMP, flow data and log collection
• Set alert thresholds that avoid noise

Tools & tech: Network

• Zeek documentation
• Prometheus — Overview

Check yourself before finishing: can you design, build and troubleshoot a small network without notes?

• Design an addressing plan with VLANs
• Configure routing, DHCP and DNS
• Diagnose a fault methodically

• CyberA4U CTF Arena — practice challenges

You have covered the core of network administration. Keep practicing in the lab, consider a certification such as CompTIA Network+ or Cisco CCNA, and continue with the Linux Administrator or Network Security roadmaps.

• Keep a lab you can rebuild in under an hour
• Pick your next roadmap
• Share one write-up of a problem you solved

• CyberA4U CTF Arena — practice challenges