Aruba Switching Professional flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

VLAN Trunk 802.1Q

A trunk link carries multiple VLANs by adding a 4-byte tag to Ethernet frames; the tag includes a 12-bit VLAN ID (1-4094). Native VLAN frames are untagged.

Spanning Tree Root Bridge

The switch with the lowest bridge ID (priority + MAC) becomes root bridge. All ports on root bridge are designated and forward; other switches select root ports and designated ports.

Link Aggregation LACP

Bundles multiple physical links into one logical link to increase bandwidth and redundancy. LACP (802.3ad) negotiates the bundle; all ports must have matching speed, duplex, and VLAN config.

OSPF Cost Calculation

OSPF interface cost = reference bandwidth (default 100 Mbps) divided by interface bandwidth. Lower cost is preferred; cost is used in SPF tree calculation.

CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance is the media access method for 802.11 WLANs. It uses inter-frame spaces and random backoff; optional RTS/CTS reduces hidden node collisions.

PoE 802.3af vs 802.3at

802.3af provides up to 15.4W per port over two pairs. 802.3at (PoE+) provides up to 30W using two pairs or up to 60W with four-pair (Type 3/4).

Wavelength Formula

Wavelength λ (meters) = speed of light c (3×10^8 m/s) divided by frequency f (Hz). Example: 2.4 GHz gives λ ≈ 0.125 m or 12.5 cm.

dBm and Milliwatts

dBm is a logarithmic power unit relative to 1 mW: P(dBm) = 10 log10(P(mW)/1mW). 0 dBm = 1 mW, 10 dBm = 10 mW, 20 dBm = 100 mW.

3 dB Rule

A +3 dB change doubles power; -3 dB halves power. A +10 dB change multiplies power by 10; -10 dB divides by 10. Used for quick signal strength estimates.

Free Space Path Loss

FSPL (dB) = 20 log10(d) + 20 log10(f) + constant, where d is distance and f is frequency. Doubling distance adds about 6 dB loss; doubling frequency also adds 6 dB.

Non-Overlapping 2.4 GHz Channels

In the 2.4 GHz band, only channels 1, 6, and 11 are non-overlapping (in North America) because each channel is 20 MHz wide and spacing is 5 MHz.

SNR Signal-to-Noise Ratio

SNR (dB) = signal strength (dBm) - noise floor (dBm). Higher SNR indicates a cleaner signal; typical minimum for reliable 802.11n/ac is 20-25 dB.

MIMO Spatial Multiplexing

MIMO uses multiple antennas to transmit multiple data streams simultaneously (spatial multiplexing), increasing throughput. 802.11n supports up to 4 streams; 802.11ac up to 8.

WPA2 vs WPA3

WPA2 uses AES-CCMP encryption with PSK or 802.1X. WPA3 replaces PSK with SAE for forward secrecy and adds 192-bit security in enterprise mode.

802.1X Three Roles

Supplicant (client device), authenticator (switch or AP), and authentication server (RADIUS). EAP messages are encapsulated in RADIUS between authenticator and server.

RADIUS Ports

RADIUS uses UDP port 1812 for authentication and authorization, and UDP port 1813 for accounting. Legacy ports 1645/1646 are deprecated.

MAC Authentication Bypass

MAB is an 802.1X fallback that authenticates devices by MAC address against a RADIUS server. It is vulnerable to spoofing and should be used with other controls.

DHCP Snooping

A Layer 2 security feature that filters untrusted DHCP messages and builds a binding table of legitimate client IP-to-MAC mappings. It prevents rogue DHCP servers.

IPsec ESP and AH

ESP provides confidentiality (encryption) and integrity; AH provides integrity and authentication but no encryption. Both can operate in transport or tunnel mode.

Port Security Violation Modes

Protect: drops frames from unknown MACs silently. Restrict: drops and logs. Shutdown: puts port into err-disabled state. Limits MAC addresses per port.

MAC Address Table Learning

A switch learns source MAC addresses and associated ports. Unknown destination MACs are flooded. Entries age out after a default of 300 seconds.

PortFast

A Spanning Tree feature that immediately transitions access ports to forwarding state, bypassing listening and learning. Use only on ports connected to end devices.

Inter-VLAN Routing

Routing between VLANs requires a Layer 3 device with an interface per VLAN (SVI on a multilayer switch) or router subinterfaces with 802.1Q encapsulation.

LACP Modes

Active mode initiates LACP negotiation; passive mode responds. At least one side must be active. Use 'show lacp interfaces' to verify status.

Wireless Client Association

Client connects to AP via probe, authentication, and association. 802.11 management frames handle these steps; 802.1X/EAP occurs after association if configured.

Native VLAN Mismatch

If native VLANs differ on two ends of a trunk, untagged frames are placed in different VLANs, causing connectivity issues and potential VLAN hopping. Ensure native VLAN matches.

SNMP Ports

SNMP agent listens on UDP port 161 for requests; traps are sent to UDP port 162. SNMPv3 adds authentication and encryption (authPriv).

Syslog Severity Levels

Levels 0 (emergency) to 7 (debug). Lower numbers are more severe. Configure logging trap level to control which messages are sent to syslog server.

sFlow

A sampling technology that provides traffic monitoring by sampling packets and sending flow data to a collector. Supported on Aruba switches for network analysis.

NTP Synchronization

Network Time Protocol synchronizes clocks across devices. Accurate time is essential for log correlation, certificate validation, and troubleshooting.

Port Mirroring SPAN

Copies traffic from one or more source ports to a destination monitoring port for analysis. Also called SPAN (Switched Port Analyzer).

ARM Adaptive Radio Management

Aruba technology that automatically adjusts AP channel and power settings to optimize RF coverage and performance, reducing interference and improving client experience.