Exam 350-401 topic 1 question 106 discussion

Answer should be D; let's look: https://www.cisco.com/c/en/us/support/docs/wireless/4400-series-wireless-lan-controllers/107606-dns-wlc-config.html#anc5

A is ok The Lightweight AP (LAP) can discover controllers through your domain name server (DNS). For the access point (AP) to do so, you must configure your DNS to return controller IP addresses in response to CISCO-LWAPP-CONTROLLER.localdomain, where localdomain is the AP domain name. When an AP receives an IP address and DNS information from a DHCP server, it contacts the DNS to resolve CISCO-CAPWAP-CONTROLLER.localdomain. When the DNS sends a list of controller IP addresses, the AP sends discovery requests to the controllers. The AP will attempt to resolve the DNS name CISCO-CAPWAP-CONTROLLER.localdomain. When the AP is able to resolve this name to one or more IP addresses, the AP sends a unicast CAPWAP Discovery Message to the resolved IP address(es). Each WLC that receives the CAPWAP Discovery Request Message replies with a unicast CAPWAP Discovery Response to the AP. Reference: https://www.cisco.com/c/en/us/support/docs/wireless/4400-series-wireless-lan-controllers/107606-dns-wlc-config.html

It's D. Step 1. The LAP sends discovery requests to controllers through the various discovery algorithms and builds a controller list.(This includes defaut DNS name of WLC) Step 2. Send a discovery request to every controller on the list and wait for the controller discovery reply Step 3 . send a join request to a controller in this order (only if the AP received a discovery reply from it): Primary Controller system name (previously configured on LAP). Secondary Controller system name (previously configured on LAP). Tertiary Controller system name (previously configured on LAP). Source : https://www.cisco.com/c/en/us/support/docs/wireless/5500-series-wireless-controllers/119286-lap-notjoin-wlc-tshoot.html#backinfo

Straight out of 31 days until your ENCORE. DHCP vendor option: When a Cisco AP sends a DHCP discover request, it uses the Cisco vendor option, which is option 43 with IPv4 and option 52 with IPv6. If the DHCP server is configured to respond to these options, it sends a list of Cisco controller IP addresses to the AP in the DHCP ACK message. The AP then uses this information to send a unicast discovery request to each of the controllers.

it's about join

C is the correct one

D is correct

Here is why C is correct: During the CAPWAP (Control and Provisioning of Wireless Access Points) discovery and join process, if multiple Wireless LAN Controllers (WLCs) respond to the CISCO-CAPWAP-CONTROLLER.localdomain hostname, the LAP (Lightweight Access Point) sends an "Join Response" message to each of the responding WLCs. This message contains information about the LAP itself and its capabilities. The WLCs then evaluate this information and decide whether to accept the LAP's join request based on factors such as current load, configuration, and other parameters. If multiple WLCs accept the LAP's join request, typically only one of them becomes the primary controller for that LAP, while the others may act as backup controllers or standby controllers in case of failover.

Wireless LAN Controller DNS Discovery The Lightweight AP (LAP) can discover controllers through your domain name server (DNS). For the access point (AP) to do so, you must configure your DNS to return controller IP addresses in response to CISCO-LWAPP-CONTROLLER.localdomain, where localdomain is the AP domain name. When an AP receives an IP address and DNS information from a DHCP server, it contacts the DNS to resolve CISCO-CAPWAP-CONTROLLER.localdomain. When the DNS sends a list of controller IP addresses, the AP sends discovery requests to the controllers. so, it wil be D The AP will attempt to resolve the DNS name CISCO-CAPWAP-CONTROLLER.localdomain. When the AP is able to resolve this name to one or more IP addresses, the AP sends a unicast CAPWAP Discovery Message to the resolved IP address(es). Each WLC that receives the CAPWAP Discovery Request Message replies with a unicast CAPWAP Discovery Response to the AP.

D. Unicast discovery request to each WLC. The LAP sends unicast discovery requests individually to each WLC that resolves the domain name in order to establish a connection with the appropriate controller. This allows the LAP to communicate with the specific WLC that responds to its discovery request.

When multiple WLCs respond to the CISCO-CAPWAP-CONTROLLER.localdomain hostname during the CAPWAP discovery and join process, the LAP sends a unicast discovery request to each WLC that responded. This process is called the discovery response mechanism. In this mechanism, each WLC that receives a discovery request from the LAP sends a discovery response to the LAP with its IP address. If multiple WLCs respond with the same hostname, the LAP sends a discovery request to each of them. The LAP then selects the first WLC that responded to the discovery request and sends a join request to that WLC. If the first WLC does not respond, the LAP sends a join request to the next WLC in the list that responded to the discovery request, and so on.

Selected Answer: D Once the DNS name has been resolved a unicast Discovery Request will be sent to the WLC IP/s.

https://www.cisco.com/c/en/us/support/docs/wireless/4400-series-wireless-lan-controllers/107606-dns-wlc-config.html#anc5

Answer is D

I Think is D too D is correct https://www.cisco.com/c/en/us/support/docs/wireless/4400-series-wireless-lan-controllers/107606-dns-wlc-config.html#anc5

From the K Wallace cert guide: "When an AP has finished the discovery process, it should have built a list of live candidate controllers. Now it must begin a separate process to select one WLC and attempt to join it. " So, I vote for C.

C is correct