Networking Security
Network Fundamentals
How networks work: models, standards, addressing, protocols, media and everyday commands.
- 36 notes
- 294 minutes of reading
- Introduction to computer networks: purpose, benefits and risksWhat a computer network is, the words engineers use (node, host, data rate), why organisations build networks, the risks they bring and how networks are judged. 6 min · Beginner
- Data communication: components, data flow and connection typesThe five parts of every data communication system, simplex vs half-duplex vs full-duplex, and point-to-point vs multipoint links, with diagrams. 6 min · Beginner
- Network system types: peer-to-peer, client-server, cloud, cluster and moreHow networks are organised: peer-to-peer vs client-server (with a comparison table), cloud computing and IaaS/PaaS/SaaS, clusters, centralised and virtualised systems. 9 min · Beginner
- Network types: LAN, WAN, MAN, VPN, SAN, CAN, intranet and extranetThe main kinds of network by size and purpose: PAN, LAN, MAN, WAN, VPN, SAN and CAN, plus intranets, extranets and internetworks, with diagrams. 8 min · Beginner
- Networking standards: who makes them and the IEEE 802 familyWhy standards matter, the main standards organisations (ANSI, IEEE, ISO, IETF, W3C), the IEEE 802 family, Ethernet (802.3) and the Wi-Fi generations (802.11). 7 min · Beginner
- The OSI and TCP/IP models: layers, functions and encapsulationWhy network models exist, the seven OSI layers and what each does, how data is encapsulated, the four-layer TCP/IP model and how the two map together. 10 min · Beginner
- Application layer protocols and their ports: FTP, SSH, Telnet, SMTP, POP3, DNS, HTTP(S), DHCP, SNMPWhat a protocol is and how the main application protocols work: file transfer, remote access, email, DNS, web, DHCP and SNMP, with port numbers and security notes. 10 min · Beginner
- TCP, UDP, IP, ICMP and ARP: the transport and internet layer protocolsHow TCP and UDP deliver data (and when to use each), what IP does, how ICMP reports errors and powers ping and traceroute, and how ARP finds MAC addresses. 8 min · Intermediate
- IPv4 addressing: classes, subnet masks, private ranges and subnettingHow a 32-bit IPv4 address is built, address classes A to E, default subnet masks and the AND operation, public vs private addresses and an introduction to subnetting, with practice questions. 11 min · Intermediate
- IPv6 explained: why we need it, address structure, shortening rules and address typesWhy IPv6 replaced IPv4's limited address space, its main features, how to read and shorten a 128-bit address, EUI-64 interface IDs and the global, unique local and link-local address types. 10 min · Intermediate
- Network topologies: bus, star, ring, mesh, tree, hybrid and the hierarchical modelPhysical and logical topologies explained with diagrams: bus, star, ring, mesh (full and partial), tree and hybrid, plus the core, distribution and access model used in real networks. 8 min · Beginner
- Transmission media and network software: twisted pair, coax, fibre, wireless, client and server softwareThe physical and wireless media that carry network signals (UTP vs STP, coaxial, single-mode and multimode fibre, microwave, satellite, cellular, infrared) and the software that runs networks. 8 min · Beginner
- Network services: DHCP, static vs dynamic IP, DNS, NAT and routingThe services that make networks work: how DHCP leases addresses (DORA, scopes, relay), when to use static or dynamic IPs, how DNS and NAT work, and static vs dynamic routing. 9 min · Intermediate
- Windows networking and security commandsThe important Windows commands for checking IP settings, testing connectivity, resolving names, viewing connections, managing the firewall and checking users and updates, from Command Prompt and PowerShell. 6 min · Beginner
- Linux networking and security commandsThe important Linux commands for interfaces and addresses, connectivity tests, DNS, open ports and sockets, firewalls (ufw, firewalld, nftables), SSH and logs. 6 min · Beginner
- Ethernet frames and MAC addresses: structure, types and how to read themWhat is inside an Ethernet frame, how a 48-bit MAC address is built, the difference between unicast, multicast and broadcast frames, and why frame size and the FCS matter when you troubleshoot. 7 min · Beginner
- ARP explained: how IPv4 finds MAC addresses, gratuitous ARP, proxy ARP and ARP spoofingHow the Address Resolution Protocol maps IPv4 addresses to MAC addresses, what the ARP cache does, when hosts ARP for the gateway, gratuitous and proxy ARP, and how ARP spoofing works and is stopped. 7 min · Beginner
- The IPv4 packet header: TTL, fragmentation, DSCP and the protocol field explainedA field-by-field tour of the IPv4 header, with the practical side: how TTL stops loops, how fragmentation and the Don't Fragment bit cause MTU problems, and how DSCP and the protocol field are used by firewalls and QoS. 8 min · Intermediate
- VLSM, CIDR and route summarisation with worked examplesHow classless addressing (CIDR) replaced classes, how to carve one block into different-sized subnets with VLSM, and how to summarise contiguous networks into a single route, with step-by-step worked examples. 9 min · Intermediate
- IPv6 Neighbour Discovery, SLAAC and DHCPv6: how IPv6 hosts get addressesHow IPv6 replaces ARP and much of DHCP with the Neighbour Discovery Protocol: router and neighbour messages, SLAAC, duplicate address detection, solicited-node multicast, DHCPv6 options and RA Guard. 8 min · Intermediate
- TCP in depth: header, handshake, windowing, congestion control and resetsHow TCP delivers data reliably: the header fields and flags, sequence and acknowledgement numbers, the handshake and teardown, flow control with windows, congestion control, and what resets and retransmissions tell you when troubleshooting. 9 min · Intermediate
- ICMP, ping and traceroute: message types and how to read the resultsWhat ICMP is for, the message types every engineer should recognise, exactly how ping and traceroute use them, how to read stars and timeouts, and which ICMP messages a firewall must allow. 8 min · Beginner
- CDP and LLDP: discovering neighbours, mapping networks and locking them downHow the Cisco Discovery Protocol and the Link Layer Discovery Protocol let devices advertise themselves to direct neighbours, how to use them to map a network and find where a device is plugged in, LLDP-MED for IP phones, and when to turn them off. 7 min · Beginner
- Collision domains and broadcast domains: what they are and how to count themWhat a LAN segment is, how early Ethernet shared one cable with CSMA/CD, why switches split collision domains and routers split broadcast domains, how VLANs fit in, and a worked example of counting both in a small network. 7 min · Beginner
- Binary and hexadecimal for network engineers: conversions you will use every dayA practical guide to the two number systems behind networking: binary place values, converting decimal to binary and back, subnet mask octet values, hexadecimal digits and nibbles, and where hex appears in MAC addresses, IPv6 and packet captures. 8 min · Beginner
- Subnetting step by step: the binary method, the fast decimal method and planning from requirementsWhat subnetting is and why we do it, how to find the network, first host, last host and broadcast address of any IPv4 address in binary, the faster block-size method in decimal, and how to choose a mask from a number of subnets or hosts. 10 min · Intermediate
- How to take networking notes that you will actually useA practical method for studying networking and preparing for certifications such as CCNA: a simple note template per topic, lab journals, command cheat sheets, drawing your own diagrams, self-testing with questions and reviewing on a schedule. 7 min · Beginner
- IPv4 versus IPv6: the real differences and how networks run bothA clear comparison of IPv4 and IPv6: address size and notation, header changes, broadcast versus multicast, ARP versus Neighbour Discovery, fragmentation and MTU, NAT and security, plus the main ways networks run both protocols during the transition. 8 min · Beginner
- IPv6 by hand: address types, finding the prefix, EUI-64 and solicited-node multicastWorked IPv6 calculations: a quick map of unicast, multicast and anycast address types, finding the prefix of an address for /48, /56, /64 and awkward lengths, building an EUI-64 interface ID step by step, and working out solicited-node multicast and multicast MAC addresses. 9 min · Intermediate
- TCP window size and window scaling: why fast links can still feel slowHow the TCP receive window controls how much data can be in flight, why the original 64 KB limit throttles long-distance links, how to calculate the bandwidth-delay product, how the window scale option works and how to check and troubleshoot it. 8 min · Intermediate
- DHCP on Cisco IOS: server pools, exclusions, static bindings and DHCP clientsHow to run a DHCP server on a Cisco router or Layer 3 switch: pools, excluded ranges, options and leases, how to reserve an address with a static binding, and how to make a router interface a DHCP client. 9 min · Intermediate
- DHCP relay, APIPA and troubleshooting DHCP step by stepWhy DHCP needs a relay agent when the server is on another subnet, how ip helper-address and the giaddr field work, what an APIPA 169.254 address tells you, and a structured way to troubleshoot clients that do not get an address. 9 min · Intermediate
- The Cisco IOS file system: flash, NVRAM, copying files and the running configurationA practical guide to the Cisco IOS file system: what flash, NVRAM and the system file system hold, how to list and copy files, how to back up and restore configurations, and why copying into the running configuration merges rather than replaces. 8 min · Beginner
- Syslog on Cisco IOS: message format, severity levels and logging destinationsHow to read a Cisco IOS syslog message (facility, severity and mnemonic), what the eight severity levels from 0 to 7 mean, and how to send logs to the console, buffer, terminal sessions and a central syslog server with accurate timestamps. 8 min · Beginner
- NTP on Cisco IOS: stratum, configuration, NTPv4, authentication and troubleshootingWhy accurate time matters on a network, how NTP strata and associations work, how to configure Cisco IOS as an NTP client and server with authentication, what NTPv4 added (including IPv6), and how to fix devices that will not synchronise. 9 min · Intermediate
- SNMP in depth: managers, agents, MIBs, OIDs, traps and SNMPv3How the Simple Network Management Protocol works: managers and agents, the MIB and object identifiers, get, set, trap and inform messages, the differences between SNMPv1, v2c and v3, and a secure SNMPv3 configuration on Cisco IOS. 9 min · Intermediate