Computer networking guides, organized to help you progress.
Move through connected learning clusters covering fundamentals, IP addressing, subnetting, switching, routing, services, troubleshooting, and security.
Start with the concept you need, then follow the technical relationship.
Each cluster groups a pillar guide with its related topics. You can study in sequence or jump directly to a specific question without losing the surrounding context.
Networking fundamentals
12 guidesCore concepts, architecture, layers, Ethernet, devices, media, topologies, and protocols.
Networking Fundamentals
Learn the essential building blocks of computer networks: devices, media, protocols, network types, topologies, and the concepts that prepare you for IP addressing, OSI/TCP-IP, routing, security, and subnetting.
Open guide 02Network Architecture: How Networks Are Organized and Why
Understand how devices, links, layers, protocols, addressing, and design roles fit together to form a network architecture, from a small LAN to a hierarchical campus design.
Open guide 03OSI Model: The 7 Layers and Their Relationship to TCP/IP
Learn the OSI model clearly: the seven layers, what each layer does, encapsulation, its relationship to TCP/IP, and practical examples for understanding how data moves through a network.
Open guide 04Ethernet: Frames, MAC Addresses, Switching and LAN Operation
Learn how Ethernet works below IP: frame structure, MAC addresses, switching decisions, full duplex, MTU, media, and delivery inside a LAN.
Open guide 05MAC Addresses and ARP: How Devices Find Each Other on a LAN
Understand the difference between IP and MAC addressing, how ARP resolves IPv4 neighbors, what the ARP cache stores, how switches participate, and what changes in IPv6.
Open guide 06Network Protocols: TCP/IP, DNS, HTTP, Routing and Security
A structured guide to the protocols that make modern networks work: TCP/IP, TCP and UDP, DNS, DHCP, HTTP/HTTPS, routing protocols, security protocols, and newer technologies such as QUIC and HTTP/3.
Open guide 07TCP vs UDP: Ports, Connections, Reliability and Datagrams
Understand TCP and UDP at the transport layer: ports, sockets, handshakes, sequence numbers, retransmission, flow control, datagrams, MSS/MTU, and troubleshooting.
Open guide 08ICMP and ICMPv6: Ping, Errors, TTL and Network Diagnostics
Learn ICMP and ICMPv6: Echo and ping, Destination Unreachable, Time Exceeded, TTL/Hop Limit, Path MTU Discovery, traceroute, filtering, and practical diagnostics.
Open guide 09Network Devices: Switches, Routers, Layer 3 Switches and Firewalls
Understand what happens inside common network devices: MAC tables, collision and broadcast domains, ARP, Layer 2 vs Layer 3 forwarding, routing, and stateful firewall inspection.
Open guide 10Network Transmission Media: Copper, Fiber and Wi-Fi at Layer 1
Copper, fiber, and Wi-Fi explained from a practical Layer 1 perspective: distance, shielding, optics, connectors, PoE, interference, capacity, and how physical choices create or prevent failures.
Open guide 11Network Topologies: Star, Tree, Bus, Ring and Mesh Explained
Understand network topology and the main physical and logical patterns: star, tree, bus, ring, and mesh, including their trade-offs for scalability, redundancy, cost, and failure domains.
Open guide 12Types of Computer Networks: PAN, LAN, MAN, WAN and More
A home Wi-Fi network and a network spanning continents solve very different problems. Learn PAN, LAN, MAN, WAN, SAN, VLAN, and VPN concepts and where each one fits.
Open guideIP addressing
2 guidesIPv4, IPv6, and the concepts that connect addressing to network design.
IP Addressing: IPv4, IPv6, Subnetting and CIDR
Master IP addressing from the fundamentals: IPv4 and IPv6, prefixes, private addressing, CIDR, subnetting, VLSM, gateways, and practical address-plan design.
Open guide 02IPv6: Addresses, Prefixes, SLAAC and Neighbor Discovery
Learn IPv6 from the ground up: 128-bit notation, compression, address types, prefixes, link-local addressing, Neighbor Discovery, SLAAC, DHCPv6, and operational differences from IPv4.
Open guideSubnetting
3 guidesSubnets, FLSM, and VLSM as a practical IPv4 planning cluster.
Subnetting Guide: IPv4 Subnets Step by Step
Learn IPv4 subnetting step by step: network and broadcast addresses, masks, CIDR prefixes, block size, host ranges, FLSM, VLSM, worked examples, and validation.
Open guide 02FLSM Subnetting Step by Step
Learn fixed-length subnetting: choose one child prefix, calculate block size, divide a parent network into equal subnets, and verify network, broadcast, and host ranges.
Open guide 03VLSM Subnetting Step by Step
Learn variable-length subnetting: size each requirement, allocate the largest blocks first, respect CIDR boundaries, prevent overlaps, and build efficient IPv4 address plans.
Open guideSwitching and Layer 2
6 guidesEthernet switching, VLANs, trunks, STP/RSTP, link aggregation, and inter-VLAN routing.
Ethernet Switching: How a Switch Learns and Forwards Frames
Understand how an Ethernet switch works internally: MAC tables, forwarding, flooding, broadcast domains, VLAN context, Layer 2 loops, and practical troubleshooting.
Open guide 02VLANs: Segmenting an Ethernet Network Step by Step
Learn what a VLAN is, how it separates broadcast domains, how access ports work, and how VLANs connect to trunks and inter-VLAN routing.
Open guide 03802.1Q Trunks: Carrying Multiple VLANs over One Link
Understand IEEE 802.1Q trunking: VLAN tags, VIDs, access and trunk ports, native VLANs, allowed VLANs, router-on-a-stick, security, and troubleshooting.
Open guide 04STP and RSTP: Preventing Loops in Switched Networks
Learn spanning tree from the ground up: root bridge, BPDUs, path cost, port roles, convergence, RSTP, protection features, VLAN context, and troubleshooting.
Open guide 05EtherChannel and LACP: Ethernet Link Aggregation Explained
Learn link aggregation and LACP: LAGs, per-flow load distribution, redundancy, member compatibility, trunks, spanning tree, failure behavior, and troubleshooting.
Open guide 06Inter-VLAN Routing: SVIs, Router-on-a-Stick and Gateways
Learn how VLANs communicate through Layer 3 routing: default gateways, SVIs, router-on-a-stick, 802.1Q trunks, DHCP relay, policy, redundancy, and troubleshooting.
Open guideWireless access
1 guideFundamentals and operation of WLANs based on the IEEE 802.11 family.
Routing and IP connectivity
9 guidesLayer 3 decisions: routing tables, static routes, OSPF, NAT/PAT, BGP, FHRP, and route summarization.
IP Routing: How Routers Choose Paths
Learn routing from the ground up: routing tables, next hops, longest prefix match, static and dynamic routes, default routes, ECMP, IPv4/IPv6, and troubleshooting.
Open guide 02Routing Tables: Prefixes, Next Hops and Active Routes
Learn how to read a routing table: RIB and FIB, connected/static/dynamic routes, longest prefix match, default routes, recursive next-hop resolution, metrics, and ECMP.
Open guide 03Static Routes: Next Hops, Defaults and Backup Paths
Master IPv4 and IPv6 static routing: next hops, outgoing interfaces, default routes, floating statics, host and discard routes, tracking, documentation, and troubleshooting.
Open guide 04OSPF: Neighbors, LSDB, SPF, Cost and Areas
Learn OSPF from the ground up: link-state operation, Hello packets and adjacencies, LSAs and the LSDB, SPF, cost, DR/BDR, Area 0, OSPFv2/OSPFv3, convergence, and troubleshooting.
Open guide 05NAT and PAT: IPv4 Address and Port Translation
Understand NAT, NAPT/PAT, RFC 1918 private addressing, translation tables, port forwarding, the relationship with firewalls, operational limits, and troubleshooting.
Open guide 06Supernetting and Route Summarization
Learn route summarization with common binary prefixes, alignment, exact aggregates, covering summaries, longest prefix match, discard routes, and hierarchical address design.
Open guide 07BGP: Autonomous Systems, Attributes and Routing Policy
Learn BGP from the ground up: autonomous systems, eBGP and iBGP, TCP sessions, NLRI and path attributes, policy, filtering, aggregation, security, scaling, and troubleshooting.
Open guide 08First-Hop Redundancy: VRRP and HSRP
Learn first-hop redundancy with VRRP and HSRP: virtual IP/MAC identities, priorities, tracking, failover, Layer 2 dependencies, load-sharing design, and troubleshooting.
Open guide 09VRF: Separate Routing Tables and Network Virtualization
Understand VRF and VRF-lite: separate routing tables, interface membership, overlapping address spaces, route leaking, MPLS L3VPN context, shared services, security, and troubleshooting.
Open guideNetwork services
6 guidesOperational services including DHCP, DNS, NTP, SNMP/Syslog observability, and QoS.
Network Services: DHCP, DNS, NTP, Monitoring and QoS
Learn how DHCP, DNS, NTP, SNMP, Syslog, and QoS work, how they depend on IP connectivity, and how to troubleshoot them as one operational system.
Open guide 02DHCP: How Hosts Obtain IP Configuration
Learn DHCPv4 and DHCPv6: DORA, leases, scopes, reservations, relay agents, options, UDP ports, address exhaustion, and troubleshooting.
Open guide 03DNS: How Name Resolution Works
Learn DNS: recursive resolvers, authoritative servers, zones, delegation, caching, TTL, transport, DNSSEC, and the records you use most often.
Open guide 04NTP: Time Synchronization in Networks
Learn NTP: stratum, offset, delay, drift, UDP 123, time sources, internal design, security, and troubleshooting.
Open guide 05SNMP and Syslog: Monitoring, Metrics and Event Logging
Learn SNMP and Syslog: manager/agent roles, MIBs and OIDs, polling, traps and informs, SNMPv3, Syslog severities, and observability design.
Open guide 06QoS: Classification, Queues, Policing and Shaping
Learn QoS: classification, DSCP, queues, scheduling, policing, shaping, DiffServ, congestion, measurement, and troubleshooting.
Open guideNetwork troubleshooting
3 guidesDiagnostic methodology, operating-system commands, and packet analysis with Wireshark.
Network Troubleshooting: A Systematic Diagnostic Method
Learn to troubleshoot networks systematically: define the scope, validate each layer and control plane, gather evidence, and prove the root cause before changing configuration.
Open guide 02Network Diagnostic Commands for Windows, Linux and macOS
A practical reference for inspecting interfaces, routes, neighbors, DNS, ports, and network paths without turning troubleshooting into random command execution.
Open guide 03Wireshark for Network Troubleshooting
Learn to capture and interpret traffic with Wireshark: choose the right capture point, filter effectively, follow conversations, and turn packets into evidence.
Open guideNetwork security
6 guidesSegmentation and defense: ACLs, VPN/IPsec, firewalls, AAA, and Layer 2 controls.
Network Security: Segmentation, Policy and Defense in Depth
Build a practical network security foundation: segmentation, least privilege, secure management, filtering, VPNs, Layer 2 controls, identity, and observability.
Open guide 02ACLs: Network Access Control Lists
Learn how access control lists match traffic, how rule order and placement affect behavior, and how to design, validate, and troubleshoot ACL policy safely.
Open guide 03VPN and IPsec: Tunnels, IKEv2 and Troubleshooting
Understand VPN and IPsec architecture, IKEv2 negotiation, ESP, tunnel mode, traffic selectors, NAT Traversal, routing, MTU, and a structured troubleshooting workflow.
Open guide 04Layer 2 Security: 802.1X, DHCP Snooping, DAI and STP Protection
Protect the LAN against local attacks and mistakes with 802.1X, DHCP snooping, Dynamic ARP Inspection, IP Source Guard, STP protections, storm control, and hardened trunks.
Open guide 05Network Firewalls: State, Zones, Rules and Troubleshooting
Learn how a network firewall applies policy with state, zones, rules, NAT, application inspection, logging, and high availability—and how to troubleshoot decisions safely.
Open guide 06AAA, RADIUS and TACACS+: Identity for Network Access and Administration
Learn AAA in network infrastructure: authentication, authorization, accounting, RADIUS, TACACS+, 802.1X integration, roles, redundancy, secure administration, and troubleshooting.
Open guideTurn an explanation into practice when you are ready.
SubnetMaster tools are connected to the same concepts covered in the library so you can verify results and experiment with your own data.
Explore tools →