CWDP CWDP Roaming and Client Mobility 2

Question 1

What is 'roam thrashing' and how can a CWDP designer mitigate it?

Accepted Answer

Clients rapidly roaming between APs of similar signal strength; mitigated by hysteresis thresholds

Answer

Roam thrashing occurs when clients oscillate between APs; RSSI hysteresis thresholds prevent roaming unless a meaningful improvement is detected.

Question 2

In a Layer 3 roaming scenario, what mechanism preserves a client's IP address when crossing subnet boundaries?

Accepted Answer

Mobility tunneling (e.g., GRE tunnel back to anchor AP)

Answer

Layer 3 roaming solutions use tunneling (GRE or proprietary) to forward client traffic back through the anchor AP, preserving the original IP.

Question 3

What is the Pairwise Master Key (PMK) caching mechanism (OKC/PKC) designed to accomplish during roaming?

Accepted Answer

Avoid full 802.1X re-authentication by caching session keys

Answer

Opportunistic Key Caching (OKC) allows clients to reuse a previously derived PMK with nearby APs, skipping the full EAP exchange.

Question 4

A hospital deploys VoWi-Fi phones. Nurse stations are 30 meters apart. What AP density consideration ensures seamless voice roaming?

Accepted Answer

Cell coverage overlap of 15–20% at -67 dBm or better

Answer

Overlapping coverage at -67 dBm ensures VoWi-Fi phones always have a strong candidate AP available before initiating a roam.

Question 5

Which metric does 802.11k neighbor reports NOT include about neighboring APs?

Accepted Answer

Current client count on the neighbor AP

Answer

802.11k neighbor reports include BSSID, channel, and regulatory information but do not report the load or client count of neighbors.

Certified Wireless Design Professional (CWDP) Practice Test