CCNA 1-3

Router

A Layer 3 device that forwards packets between networks based on IP addresses.

Switch

A Layer 2 device that forwards Ethernet frames based on MAC addresses.

NGFW (Next-Generation Firewall)

Advanced firewall that performs deep packet inspection and intrusion prevention.

IPS (Intrusion Prevention System)

Monitors and blocks suspicious traffic in real time.

Access Point (AP)

Device providing wireless connectivity to a wired LAN.

WLC (Wireless LAN Controller)

Centralized device that manages and controls multiple wireless access points.

SSID (Service Set Identifier)

The name of a wireless network broadcasted by an access point.

PoE (Power over Ethernet)

Technology delivering power and data through one Ethernet cable.

MAC (Media Access Control) Address

Unique hardware identifier assigned to a network interface card.

TCP (Transmission Control Protocol)

Connection-oriented protocol that guarantees reliable delivery of packets.

UDP (User Datagram Protocol)

Connectionless, faster protocol that does not guarantee delivery.

IPv4 (Internet Protocol version 4)

32-bit addressing system used to identify network devices.

IPv6 (Internet Protocol version 6)

128-bit addressing system designed to replace IPv4.

NAT (Network Address Translation)

Converts private IP addresses to public ones for Internet communication.

DHCP (Dynamic Host Configuration Protocol)

Automatically assigns IP addresses and network parameters to clients.

DNS (Domain Name System)

Resolves domain names to IP addresses.

VRF (Virtual Routing and Forwarding)

Allows multiple routing tables to coexist on a single router.

VLAN (Virtual Local Area Network)

Logical segmentation of a network into separate broadcast domains.

Trunk Port

Switch port carrying traffic for multiple VLANs using tagging (802.1Q).

Access Port

Switch port assigned to a single VLAN for end devices.

802.1Q

IEEE standard for VLAN trunk tagging.

Native VLAN

VLAN that carries untagged traffic on a trunk link.

LACP (Link Aggregation Control Protocol)

Combines multiple physical links into one logical link for redundancy.

STP (Spanning Tree Protocol)

Prevents switching loops in Layer 2 networks.

PVST+ (Per-VLAN Spanning Tree Plus)

Cisco’s version of STP that runs one instance per VLAN.

BPDU (Bridge Protocol Data Unit)

STP messages used to detect loops and elect root bridges.

Root Bridge

The central switch chosen by STP to manage the network topology.

PortFast

STP feature that immediately transitions ports to forwarding state (for PCs only).

BPDU Guard

STP protection that disables a PortFast port if a BPDU is received.

Root Guard

Prevents unauthorized switches from becoming the STP root.

Loop Guard

Prevents loops caused by unidirectional links.

EtherChannel

Logical bundle of multiple physical links to increase bandwidth and redundancy.

LLDP (Link Layer Discovery Protocol)

Vendor-neutral protocol for device discovery.

CDP (Cisco Discovery Protocol)

Cisco proprietary protocol for discovering neighboring Cisco devices.

WLAN (Wireless Local Area Network)

Wireless network connecting devices within a local area.

SSH (Secure Shell)

Encrypted command-line access to network devices.

Telnet

Unencrypted remote command-line protocol (deprecated for security).

TACACS+ (Terminal Access Controller Access-Control System Plus)

Cisco AAA protocol for secure authentication and authorization.

RADIUS (Remote Authentication Dial-In User Service)

AAA protocol used to authenticate network users.

AAA (Authentication, Authorization, Accounting)

Framework for managing user access and activity.

LAG (Link Aggregation Group)

Group of combined interfaces treated as one logical link.

OSPF (Open Shortest Path First)

Link-state dynamic routing protocol using Dijkstra’s algorithm.

RID (Router ID)

Unique identifier for each OSPF router (highest IP or manually set).

LSA (Link-State Advertisement)

OSPF messages that describe network topology.

DR/BDR (Designated/Backup Designated Router)

OSPF routers managing updates in broadcast networks.

Default Route (0.0.0.0/0)

Route used when no specific route matches a packet’s destination.

Static Route

Manually configured route used for fixed network paths.

Floating Static Route

Backup route activated only if the main route fails.

HSRP (Hot Standby Router Protocol)

Cisco protocol providing gateway redundancy.

VRRP (Virtual Router Redundancy Protocol)

Open standard version of HSRP for redundancy.

GLBP (Gateway Load Balancing Protocol)

Cisco protocol offering both redundancy and load balancing.

Administrative Distance (AD)

Value representing route trustworthiness; lower = more trusted.

Metric

Cost value used to choose the best path among multiple routes.

Gateway of Last Resort

Router’s default route for unknown destinations.

Point-to-Point Link

Direct connection between two devices.

Broadcast Network

Multi-access network type where routers can send to all devices.

Wildcard Mask

Inverse of a subnet mask, used in OSPF and ACLs to match IP ranges.

CLI (Command-Line Interface)

Text-based interface used to configure Cisco devices.