Question 276 of 2,015

Wireless Infrastructure →hardMultiple SelectObjective-mapped

Quick Answer

The correct answer is that an AP must have a valid certificate installed to establish a DTLS session with the WLC, because CAPWAP control traffic is encrypted using Datagram Transport Layer Security, and the AP authenticates itself to the controller via X.509 certificates during the join process. This is a foundational concept in the Cisco AP join process and discovery, where the AP first discovers the WLC using methods like DHCP option 43, DNS resolution, or a local subnet broadcast, then initiates a CAPWAP discovery and join sequence. On the ENCOR 350-401 exam, this topic tests your understanding of the full AP lifecycle, and a common trap is confusing the discovery phase (which does not require a certificate) with the secure DTLS tunnel establishment that follows. Remember that discovery is about finding the WLC, but joining requires trust—so think “discover first, then DTLS for security.” A helpful mnemonic is “D-D-C”: Discovery via DHCP/DNS, then DTLS via Certificate.

CCNP Wireless Infrastructure Practice Question

This 350-401 practice question tests your understanding of wireless infrastructure. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

Which three statements about Cisco AP join process and discovery are true? (Choose three.)

Question 1hardmulti select

Full question →

A
An AP can discover a WLC using DHCP option 43, which provides the WLC management IP address.
Correct because DHCP option 43 is a standard method for APs to learn the WLC IP address during boot.
B
An AP can discover a WLC by sending a DNS query for 'CISCO-CAPWAP-CONTROLLER.localdomain'.
Correct because APs use DNS resolution for the hostname 'CISCO-CAPWAP-CONTROLLER' to find a WLC.
C
An AP must have a valid certificate installed to establish a DTLS session with the WLC.
Correct because DTLS encryption between AP and WLC requires certificate-based authentication for secure control and data planes.
D
An AP can discover a WLC by sending an SNMP broadcast to the local subnet.
Why wrong: Incorrect because APs use CAPWAP discovery messages (broadcast or unicast), not SNMP, to find WLCs.
E
An AP can be manually configured with the primary WLC name via the AP CLI before joining.
Why wrong: Incorrect because APs do not have a CLI for such configuration; the primary WLC is typically set from the WLC side or via a pre-shared key in the AP image.

Full breakdown with real-world context →

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

An AP can discover a WLC using DHCP option 43, which provides the WLC management IP address.

APs discover WLCs via DHCP option 43, DNS, or local subnet broadcast. They use CAPWAP for control and data. The AP must have a valid certificate for DTLS. APs can be pre-configured with a primary WLC name. APs do not use SNMP to find WLCs.

Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
An AP can discover a WLC using DHCP option 43, which provides the WLC management IP address.
Why this is correct
Correct because DHCP option 43 is a standard method for APs to learn the WLC IP address during boot.
Related concept
CIDR notation defines the prefix length.
✓
An AP can discover a WLC by sending a DNS query for 'CISCO-CAPWAP-CONTROLLER.localdomain'.
Why this is correct
Correct because APs use DNS resolution for the hostname 'CISCO-CAPWAP-CONTROLLER' to find a WLC.
Related concept
CIDR notation defines the prefix length.
✓
An AP must have a valid certificate installed to establish a DTLS session with the WLC.
Why this is correct
Correct because DTLS encryption between AP and WLC requires certificate-based authentication for secure control and data planes.
Related concept
CIDR notation defines the prefix length.
✗
An AP can discover a WLC by sending an SNMP broadcast to the local subnet.
Why it's wrong here
Incorrect because APs use CAPWAP discovery messages (broadcast or unicast), not SNMP, to find WLCs.
✗
An AP can be manually configured with the primary WLC name via the AP CLI before joining.
Why it's wrong here
Incorrect because APs do not have a CLI for such configuration; the primary WLC is typically set from the WLC side or via a pre-shared key in the AP image.

Common exam traps

Common exam trap: usable hosts are not the same as total addresses

Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.

Detailed technical explanation

How to think about this question

Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.

KKey Concepts to Remember

CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.

TExam Day Tips

Write the block size before choosing the subnet.
Check whether the question asks for hosts, subnets or a specific address range.
Do not confuse /24, /25, /26 and /27 host counts.

Key takeaway

Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

Real-world example

How this comes up in practice

A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.

What to study next

Got this wrong? Here's your next step.

Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 350-401 subnetting questions on CIDR, address ranges, and subnet selection.

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FAQ

Questions learners often ask

What does this 350-401 question test?

Wireless Infrastructure — This question tests Wireless Infrastructure — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: An AP can discover a WLC using DHCP option 43, which provides the WLC management IP address. — APs discover WLCs via DHCP option 43, DNS, or local subnet broadcast. They use CAPWAP for control and data. The AP must have a valid certificate for DTLS. APs can be pre-configured with a primary WLC name. APs do not use SNMP to find WLCs.

What should I do if I get this 350-401 question wrong?

What is the key concept behind this question?

CIDR notation defines the prefix length.

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