network accesss

VLAN (Virtual Local Area Network)

A logical segmentation of a physical network that groups devices into separate broadcast domains regardless of physical location.

Access Port

A switch port configured to carry traffic for a single VLAN, typically connecting end-user devices.

Voice VLAN

A dedicated VLAN for IP telephony traffic, often paired with a data VLAN on the same port.

Default VLAN

The initial VLAN (usually VLAN 1) on a Cisco switch where all ports are assigned by default.

Trunk Port

A switch port that carries traffic for multiple VLANs using tagging.

802.1Q

The IEEE standard for VLAN tagging that inserts a tag into Ethernet frames to identify VLAN membership.

Native VLAN

The untagged VLAN on a trunk link, carrying traffic without an 802.1Q tag.

Inter-VLAN Routing

The process of forwarding traffic between different VLANs, typically using a router or Layer 3 switch.

CDP (Cisco Discovery Protocol)

A Cisco proprietary Layer 2 protocol for discovering neighboring devices.

LLDP (Link Layer Discovery Protocol)

The open standard equivalent of CDP for discovering neighboring devices.

EtherChannel

The bundling of multiple physical links into a single logical link for increased bandwidth and redundancy.

LACP (Link Aggregation Control Protocol)

The IEEE standard protocol for dynamically negotiating EtherChannels.

PAgP (Port Aggregation Protocol)

Cisco proprietary protocol for negotiating EtherChannels.

Spanning Tree Protocol (STP)

A protocol that prevents Layer 2 loops by blocking redundant paths. Lowest Bridge ID wins root election.

Root Bridge

The central reference switch in an STP topology elected by lowest Bridge ID (priority + MAC — lowest number wins).

Root Port

The port on a non-root switch with the best (lowest cost) path to the root bridge.

Designated Port

The forwarding port on each network segment closest to the root bridge.

PortFast

An STP feature that allows ports connected to end devices to transition quickly from blocking to forwarding.

BPDU Guard

A security feature that disables a port upon receiving a BPDU.

Rapid PVST+

Cisco’s implementation of Rapid Spanning Tree Protocol running per VLAN for faster convergence.

Cisco Wireless Architectures

Centralized (with WLC) or distributed (autonomous APs) designs for WLAN management.

WLC (Wireless LAN Controller)

A device that centrally manages multiple Access Points.

AP (Access Point)

A device that connects wireless clients to the wired network.

SSID (Service Set Identifier)

The name of a wireless network.

WPA2/WPA3

Wireless security protocols providing encryption and authentication.

LAG (Link Aggregation Group)

Bundling links between AP and switch or WLC for higher bandwidth.

Lightweight AP

Controller-based Access Point operating mode.