HCIP-WLAN flashcards

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

CAPWAP control port

CAPWAP control runs over UDP 5246 and is normally DTLS-encrypted; the data channel uses UDP 5247. Both must be permitted through firewalls between AP and AC.

DHCP option 43

Vendor-specific DHCP option that carries the AC IP address list to the AP. Huawei encodes it as sub-option 0x0B with the AC IPs; without it the AP falls back to broadcast or DNS discovery.

Direct forwarding

CAPWAP mode in which client data exits the AP's local uplink instead of being tunneled to the AC. Only control traffic goes to the AC, saving AC bandwidth, but service VLANs must exist on the access switch.

802.11r FT

Fast BSS Transition pre-derives PMK-R0 and PMK-R1 keys so a roaming client skips full 802.1X re-authentication. It reduces roam time to tens of milliseconds and requires a consistent mobility domain.

802.11k neighbor report

Radio Resource Measurement feature in which the serving AP sends the client a list of nearby APs with channel and BSSID. The client scans fewer channels, shortening roam discovery time.

802.11v BTM

BSS Transition Management lets the network send a request suggesting a better target AP for a client. The client may accept or reject, so it influences rather than forces roaming.

Band steering

Technique that suppresses or delays 2.4 GHz probe responses for dual-band clients so they associate on 5 GHz. It must not block 2.4-only clients and works with load balancing.

WPA2 4-way handshake

Exchange that derives the PTK from the PMK, ANonce, SNonce, and MAC addresses, and installs keys. It also proves both sides hold the PMK without transmitting it over the air.

SAE in WPA3

Simultaneous Authentication of Equals is a password-authenticated key exchange using commit and confirm frames. It provides forward secrecy and resists offline dictionary attacks, replacing the PSK handshake.

EAP-TLS

802.1X method requiring certificates on both client and server. It gives the strongest mutual authentication but needs a PKI to issue and renew client certificates.

RADIUS ports

RADIUS authentication uses UDP 1812 and accounting uses UDP 1813; legacy deployments may use 1645 and 1646. The shared secret must match on the AC and the server.

PMF 802.11w

Protected Management Frames encrypt and integrity-protect deauthentication, disassociation, and robust action frames using BIP. It is mandatory for WPA3 and recommended for WPA2 to stop deauth attacks.

WMM access categories

Four EDCA queues: Voice, Video, Best Effort, and Background. Each has its own AIFSN, CWmin, CWmax, and TXOP, so higher-priority traffic wins contention more often.

EDCA voice parameters

The Voice access category uses AIFSN 2, CWmin 3, and CWmax 7, giving it the shortest backoff and highest priority. Background uses AIFSN 7 and CWmin 15.

Co-channel interference

Interference from APs or clients transmitting on the same channel. It is managed by channel reuse distance and power planning, not by choosing a different channel width.

Adjacent-channel interference

Interference from overlapping but non-identical spectrum, such as 20 MHz channels spaced less than 20 MHz apart. It is avoided by using non-overlapping channels and proper width planning.

VRRP hot standby

Two ACs form a VRRP group sharing a virtual IP that APs use as the CAPWAP AC address. The master handles tunnels; the backup takes over on failure and APs rejoin.

HSB state sync

Hot Standby synchronizes AP sessions, STA entries, and keys from master to backup over a dedicated link. Without it, all APs must fully re-onboard after a failover.

Dual-link backup

The AP is configured with a primary and a backup AC address. If the primary CAPWAP tunnel fails, the AP tries the backup, protecting against single-AC failure without VRRP.

AC virtualization

Multiple physical ACs are pooled into one logical AC. APs are load-balanced across members and fail over within the pool, improving scale and resilience.

AP not online causes

Typical causes are no IP address, AC unreachable, missing DHCP option 43 or wrong AC address, AP not in the whitelist, certificate or DTLS mismatch, and firmware incompatibility.

Roam-history command

display station roam-history shows each roam event with source and target AP, roam time, and reason. It is the primary tool for verifying fast roaming and sticky-client behavior.

WLAN Planner

Offline planning tool that imports floor plans, sets wall attenuation, AP model, and power, then outputs coverage heat maps and AP placement. Results should be validated with a site survey.

CloudCampus onboarding

The AP gets an IP via DHCP, resolves the cloud controller through option 43 or DNS, registers with a registration code or serial number, and downloads its configuration.

802.11mc FTM

Fine Timing Measurement uses round-trip time between AP and client to estimate distance, giving indoor positioning accuracy of about one to two meters. It needs multiple APs.

Direct forwarding VLANs

In direct forwarding, client traffic exits the AP's local uplink, so service VLANs and gateways must be configured on the access switch, not only on the AC.

CAPWAP discovery order

APs discover the AC by DHCP option 43, DNS resolution, broadcast on the local subnet, or a statically configured AC address. The order is configurable on the AP.

AP whitelist authentication

The AC validates an AP by MAC or serial number before allowing it to join. Unauthenticated APs remain in a pending state and cannot carry service traffic.

Fresnel zone clearance

The ellipsoidal volume around the line-of-sight path. Obstruction within the first Fresnel zone degrades signal even without a full blockage; about 60% clearance is the design target.

Free-space path loss

FSPL in dB equals 32.44 plus 20log10(f in MHz) plus 20log10(d in km). Doubling distance or frequency adds about 6 dB of loss.

SNR and modulation

SNR is signal minus noise floor in dB. Higher-order modulation needs higher SNR: 64-QAM needs roughly 25-30 dB, while BPSK and QPSK work near 5-10 dB.

WPA3-Enterprise 192-bit

High-security mode using GCMP-256, SHA-384, and 384-bit ECDHE/ECDSA. It targets government and finance networks and requires compatible clients and RADIUS infrastructure.