IT and Tech Certifications
25 flashcards
~13 min
Networking Fundamentals (CompTIA Network plus)
Build a solid understanding of computer networking with this comprehensive flashcard deck aligned to CompTIA Network+ objectives. Networking knowledge is essential for virtually every IT role — from help desk to system administrator to network engineer....
About this deck
Build a solid understanding of computer networking with this comprehensive flashcard deck aligned to CompTIA Network+ objectives. Networking knowledge is essential for virtually every IT role — from help desk to system administrator to network engineer.
This deck covers the OSI and TCP/IP reference models, IP addressing (IPv4 and IPv6), subnetting, CIDR notation, DNS, DHCP, network devices (routers, switches, firewalls), network topologies, wireless networking (802.11 standards), VLANs, NAT, key protocols and their port numbers, and network troubleshooting. Based on publicly available CompTIA Network+ (N10-008) exam objectives.
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1. Physical (cables, signals). 2. Data Link (MAC addresses, switches, frames). 3. Network (IP addresses, routing, packets). 4. Transport (TCP/UDP, ports, segments). 5. Session (establishing/maintaining/terminating connections). 6. Presentation (encryption, compression, format). 7. Application (HTTP, FTP, DNS, SMTP — user-facing).
A 4-layer model: Application (OSI layers 5–7), Transport (OSI layer 4), Internet (OSI layer 3), Network Access/Link (OSI layers 1–2). The TCP/IP model is the practical model used on the internet.
TCP (Transmission Control Protocol): Connection-oriented, reliable, ordered, error-checked — uses handshake. Slower. Used for: HTTP/HTTPS, email, file transfer. UDP (User Datagram Protocol): Connectionless, no guarantee of delivery, faster. Used for: video streaming, VoIP, DNS, gaming.
The process to establish a TCP connection: 1. SYN — client sends synchronise request. 2. SYN-ACK — server acknowledges and sends its own SYN. 3. ACK — client acknowledges. Connection established. Closed with a four-way FIN/ACK process.
20/21: FTP (data/control). 22: SSH. 23: Telnet. 25: SMTP. 53: DNS. 67/68: DHCP. 80: HTTP. 110: POP3. 143: IMAP. 443: HTTPS. 3389: RDP. 3306: MySQL. 1433: MS SQL Server.
A numerical label assigned to each device on a network. IPv4: 32-bit, dotted decimal (e.g., 192.168.1.1), ~4.3 billion addresses — nearly exhausted. IPv6: 128-bit, hexadecimal notation (e.g., 2001:0db8::1), 340 undecillion addresses — virtually unlimited.
Addresses reserved for private networks (not routable on the internet): 10.0.0.0 – 10.255.255.255 (Class A, /8). 172.16.0.0 – 172.31.255.255 (Class B, /12). 192.168.0.0 – 192.168.255.255 (Class C, /16). NAT translates private → public IPs at the router.
Dividing a network into smaller sub-networks. CIDR notation: IP address + /prefix length (e.g., 192.168.1.0/24). The prefix length = number of network bits. /24 = 255.255.255.0 subnet mask = 256 addresses (254 usable). /25 = 128 addresses. /26 = 64. Each bit halves the number of hosts.
Translates human-readable domain names (e.g., google.com) into IP addresses (e.g., 142.250.80.46). Operates on port 53 (UDP for queries, TCP for zone transfers). Hierarchy: Root → TLD (.com, .org) → Authoritative nameserver → IP address returned.
Automatically assigns IP addresses and network configuration to devices. DORA process: Discover (client broadcasts) → Offer (server offers IP) → Request (client requests the offered IP) → Acknowledge (server confirms). Operates on ports 67 (server) and 68 (client).
Hub: Layer 1 — broadcasts all traffic to all ports (dumb, obsolete). Switch: Layer 2 — forwards frames based on MAC addresses — sends only to correct port (intelligent). Router: Layer 3 — routes packets between different networks based on IP addresses — connects LAN to WAN/internet.
A logical subdivision of a physical network — devices in the same VLAN communicate as if on the same network segment, even if physically separate. Configured on managed switches. Improves security, reduces broadcast traffic, and allows logical grouping (e.g., HR VLAN, Finance VLAN).
A router feature that translates private IP addresses to a single public IP address (and back). Allows many devices to share one public IP. PAT (Port Address Translation) or "NAT overload" uses different port numbers to distinguish traffic from different devices.
802.11a: 5GHz, 54Mbps (1999). 802.11b: 2.4GHz, 11Mbps (1999). 802.11g: 2.4GHz, 54Mbps (2003). 802.11n (Wi-Fi 4): 2.4/5GHz, 600Mbps (2009). 802.11ac (Wi-Fi 5): 5GHz, ~3.5Gbps (2013). 802.11ax (Wi-Fi 6/6E): 2.4/5/6GHz, ~9.6Gbps (2019).
2.4GHz: Longer range, better wall penetration, but more congested (shared with microwaves, Bluetooth) — slower. 5GHz: Shorter range, less congestion, faster speeds. 6GHz (Wi-Fi 6E): Even faster, least congested, shortest range. Choose 5GHz for speed near router; 2.4GHz for far-away devices.
A security device/software that monitors and controls network traffic based on rules. Packet-filtering firewall: Inspects headers (IP, port) — stateless. Stateful firewall: Tracks connection state. Application layer (proxy) firewall: Deep packet inspection. NGFW (Next-Gen Firewall): Application awareness, intrusion prevention.
Extends a private network across a public network (internet) by creating an encrypted tunnel. Makes remote users appear to be on the local network. Uses: IPSec, SSL/TLS, OpenVPN, WireGuard protocols. Types: Site-to-site VPN (connects two offices) and Remote access VPN (individual user to network).
Internet Control Message Protocol — used for network diagnostics. Not for data transfer. Tools: ping (tests connectivity — sends ICMP Echo Request, expects Echo Reply) and traceroute/tracert (maps the path to a destination, showing each hop).
Half-duplex: Communication in both directions but only one direction at a time (like a walkie-talkie). Full-duplex: Communication in both directions simultaneously (like a phone call). Modern switched Ethernet is full-duplex. Hubs force half-duplex; switches support full-duplex.
A record: Maps domain → IPv4 address. AAAA record: Maps domain → IPv6 address. CNAME: Alias — maps one domain to another. MX: Mail server for the domain. TXT: Text info (used for SPF, DKIM email verification). NS: Nameserver record. PTR: Reverse DNS (IP → domain).
An intermediary server that sits between clients and the internet. Forward proxy: Hides clients' identities from servers (privacy, content filtering). Reverse proxy: Protects servers — clients see the proxy, not the server (load balancing, caching, SSL termination). Examples: Nginx (reverse), Squid (forward).
Open Shortest Path First — a link-state interior gateway routing protocol (IGP). Each router maintains a complete map of the network topology using Dijkstra's algorithm to calculate shortest paths. Fast convergence. Hierarchical using areas to reduce overhead. Used in large enterprise networks.
A Layer 2 protocol that prevents network loops in switched networks. Loops cause broadcast storms (infinite loops of traffic). STP elects a root bridge and blocks redundant paths, activating them only if the primary path fails. RSTP is the faster modern version.
A set of techniques to manage network traffic and ensure priority delivery for time-sensitive traffic (VoIP, video conferencing) over less critical traffic (file downloads, email). Tags packets with priority levels. Essential in networks where bandwidth is shared and latency matters.
Authoritative DNS server: Holds the actual DNS records for a domain — gives definitive answers. Recursive (resolver) DNS server: Asks other DNS servers on behalf of the client to find the answer — your ISP's DNS server is usually a recursive resolver. Your computer typically queries a recursive resolver, which queries authoritative servers.