Network+ Complete
Course Module

Open Systems Interconnection model — 7-layer framework standardizing how network communication functions are divided and defined.

Protocol Data Unit — the form data takes at each OSI layer. Bit (L1), Frame (L2), Packet (L3), Segment (L4), Data (L5-7).

48-bit hardware address burned into NIC. Used at Layer 2 for local network communication. Format: AA:BB:CC:DD:EE:FF.

32-bit (IPv4) or 128-bit (IPv6) logical address used at Layer 3 to identify devices globally and enable routing across networks.

32-bit value that defines the network and host portions of an IP address. Written in dotted decimal (255.255.255.0) or CIDR notation (/24).

Classless Inter-Domain Routing — flexible IP address allocation using prefix length notation (/24) replacing fixed class boundaries.

Variable Length Subnet Masking — using different prefix lengths within the same network to allocate address space efficiently based on actual needs.

Group of devices that receive each other's broadcast messages. Routers separate broadcast domains; switches do not (without VLANs).

Network segment where data packets can collide. Each switch port creates its own collision domain. Hubs share one collision domain.

Layer 3 device that forwards packets between different networks based on IP addresses. Maintains routing tables. Breaks broadcast domains.

Layer 2 device that forwards frames using MAC address CAM table. Creates separate collision domains per port. Supports VLANs.

Security device that filters network traffic based on rules. Stateless (packet-by-packet) or stateful (connection-aware). NGFW adds L7 inspection.

Intrusion Detection System — passive monitoring tool that detects and alerts on suspicious activity. Does not block traffic.

Intrusion Prevention System — active inline device that detects AND blocks malicious traffic in real time.

Distributes incoming traffic across multiple servers to optimize performance, availability, and prevent overload.

Intermediary server between clients and the internet. Forward proxy hides clients; reverse proxy hides servers.

Network Attached Storage — file-level storage device on a network. Uses NFS/SMB. Has own IP. Multiple clients can access simultaneously.

Storage Area Network — dedicated high-speed network for block-level storage. Uses Fibre Channel or iSCSI. Appears as local disk to servers.

Wireless Access Point — device that allows wireless clients to connect to a wired network. Operates at Layer 1-2.

Transmission Control Protocol — connection-oriented Layer 4 protocol. Provides reliable, ordered delivery via 3-way handshake and acknowledgments.

User Datagram Protocol — connectionless Layer 4 protocol. Fast but no delivery guarantees. Used for DNS, streaming, gaming, DHCP.

File Transfer Protocol — TCP port 20 (data) and 21 (control). Transfers files over a network. Cleartext — insecure. Replaced by SFTP/FTPS.

SSH File Transfer Protocol — secure file transfer over SSH (port 22). Encrypts all data and credentials. Replacement for FTP.

Secure Shell — encrypted protocol (TCP 22) for remote command-line access. Replaced Telnet. Uses public/private key or password auth.

TCP port 23. Remote access protocol that transmits all data in cleartext. Insecure — should never be used in production. Replaced by SSH.

Simple Mail Transfer Protocol — TCP port 25. Sends outbound email between mail servers. Port 587 for TLS submission, 465 for SMTPS.

Domain Name System — resolves hostnames to IP addresses. UDP port 53 for queries, TCP 53 for zone transfers. Hierarchical distributed database.

Dynamic Host Configuration Protocol — UDP 67/68. Auto-assigns IP config. Process: DORA (Discover, Offer, Request, Acknowledge).

Hypertext Transfer Protocol — TCP port 80. Unencrypted web protocol. Stateless request/response model. Layer 7 application protocol.

HTTP Secure — TCP port 443. HTTP over TLS encryption. Uses SSL/TLS certificates for authentication and encryption.

Simple Network Management Protocol — UDP 161/162. Monitors and manages network devices. v3 adds encryption. Traps are unsolicited alerts.

Lightweight Directory Access Protocol — TCP/UDP 389. Queries directory services like Active Directory. LDAPS (636) adds TLS encryption.

Remote Desktop Protocol — TCP 3389. Microsoft's GUI remote access protocol. Keep behind VPN; common attack target on public internet.

Session Initiation Protocol — TCP/UDP 5060 (5061 for TLS). Sets up, modifies, terminates VoIP/video sessions. Works with RTP for media.

One-to-one network communication. Traffic sent from single source to single specific destination. Most internet traffic is unicast.

One-to-many communication to a defined group. Efficient for streaming. IPv4 range: 224.0.0.0–239.255.255.255 (Class D).

Traffic sent to one address shared by multiple nodes — delivered to the topologically nearest one. Used in CDNs and DNS.

One-to-all within a broadcast domain. Address 255.255.255.255. Routers do not forward broadcasts. IPv6 eliminates broadcast in favor of multicast.

Transmission medium using light pulses through glass/plastic. Immune to EMI. SMF for long distance, MMF for short range. Extremely high bandwidth.

Cable with copper core surrounded by metallic shield. Used for cable TV (F-type) and legacy Ethernet. RG-6 for broadband, RG-59 for CCTV.

Direct Attach Copper — twinaxial cable with SFP+/QSFP connectors. Cheaper than fiber for short data center connections. Passive or active variants.

Single-Mode Fiber — single light path, 9μm core, yellow jacket. Long-distance (100+ km). Used in WAN and ISP infrastructure. OS2 standard.

Multi-Mode Fiber — multiple light paths, 50/62.5μm core, orange/aqua jacket. Short range (~2km). OM1–OM5 grades. Used in data centers.

IEEE standard for Wi-Fi wireless networking. Multiple amendments (a/b/g/n/ac/ax) define frequencies, speeds, and features.

Subscriber Connector — square push-pull fiber connector. Older standard, still found in legacy fiber deployments. Larger than LC.

Lucent Connector — small form-factor fiber connector with latch. Most common modern fiber connector. Half the size of SC. Used in high-density environments.

Multi-fiber connector carrying 12 or 24 fibers. Used for 40G/100G high-density connections. MTP is a high-performance MPO brand.

8P8C connector for Ethernet twisted-pair cabling (Cat5e, Cat6, Cat6a). Standard wired network connector in offices and homes.

6P2C/4C connector smaller than RJ45. Used for telephone lines and DSL modems. Not compatible with Ethernet.

Bayonet Neill-Concelman — twist-lock coaxial connector. Used in CCTV cameras, legacy 10BASE2 Ethernet, and test equipment.

Screw-on coaxial connector used for cable TV, satellite dishes, and broadband internet (DOCSIS modems).

Small Form-factor Pluggable — hot-swappable transceiver for 1 Gbps (SFP) or 10 Gbps (SFP+). Fiber or copper via DAC cable.

Quad SFP — 4-lane transceiver. QSFP28 = 100G. Used in high-bandwidth spine switches and server links.

All devices connect to a central switch/hub. Most common LAN topology. Easy troubleshooting but center is a single point of failure.

Every device connects to every other. Highly redundant. n(n-1)/2 connections needed. Used in WAN/critical networks.

Modern data center topology. Every leaf connects to every spine. Equal latency (2 hops), optimized for east-west traffic.

Core/Distribution/Access layers. Traditional enterprise design. Core for speed, Distribution for routing/policy, Access for endpoints.

Core and Distribution layers merged. Cost-effective for smaller networks. Risk of becoming a bottleneck as network grows.

Defines private IP address ranges not routable on the internet: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.

Automatic Private IP Addressing — 169.254.0.0/16. Self-assigned when DHCP fails. Indicates DHCP is broken. Only communicates locally.

Network Address Translation — translates private IPs to public IPs at the router/firewall. PAT (Port Address Translation) shares one public IP among many devices.

Virtual Private Cloud — isolated virtual network in a cloud provider. You control subnets, routing, gateways, and security rules.

Network Functions Virtualization — replacing dedicated hardware appliances (routers, firewalls) with software on commodity servers.

Virtual firewall at instance level in cloud environments. Stateful — return traffic automatically permitted. Applied to VMs/instances.

Network Access Control List — stateless firewall at subnet level in cloud. Rules processed in numbered order. Must define both inbound and outbound rules.

Infrastructure as a Service — cloud model where provider manages hardware; you manage OS, runtime, and applications.

Platform as a Service — provider manages infrastructure and OS; you manage applications and data only.

Software as a Service — provider manages everything; you just use the application. Examples: Gmail, Microsoft 365, Salesforce.

Cloud component that allows VPC resources in public subnets to communicate with the internet.

Cloud component that lets private subnet instances reach the internet for outbound traffic without being publicly accessible.

Address Resolution Protocol — maps IP addresses to MAC addresses on a local network. Broadcasts "who has IP x.x.x.x?" and caches responses.

Open Shortest Path First — link-state interior routing protocol. Uses Dijkstra algorithm. Fast convergence. Hierarchical with areas.

Border Gateway Protocol — the internet's routing protocol. Path-vector. Used between ISPs and for cloud multi-homing. Exterior Gateway Protocol.

Virtual LAN — logically segments a switch into separate networks. Devices on different VLANs cannot communicate without a router (Layer 3 switch).

Spanning Tree Protocol — prevents Layer 2 loops in switched networks by blocking redundant paths and electing a root bridge.

Transport Layer Security / Secure Sockets Layer — cryptographic protocol providing encryption, authentication, and integrity. TLS 1.3 is current standard.

Wavelength Division Multiplexing — transmitting multiple wavelengths of light simultaneously on a single fiber. DWDM for ultra-dense deployments.

Control And Provisioning of Wireless Access Points — protocol used between wireless LAN controller and lightweight access points.