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Exam 350-401 topic 1 question 186 discussion

Actual exam question from Cisco's 350-401
Question #: 186
Topic #: 1
[All 350-401 Questions]

A company has an existing Cisco 5520 HA cluster using SSO. An engineer deploys a new single Cisco Catalyst 9800 WLC to test new features. The engineer successfully configures a mobility tunnel between the 5520 cluster and 9800 WLC. Clients connected to the corporate WLAN roam seamlessly between access points on the 5520 and 9800 WLC. After a failure on the primary 5520 WLC, all WLAN services remain functional; however, clients cannot roam between the 5520 and 9800 controllers without dropping their connection. Which feature must be configured to remedy the issue?

  • A. mobility MAC on the 5520 cluster
  • B. mobility MAC on the 9800 WLC
  • C. new mobility on the 5520 cluster
  • D. new mobility on the 9800 WLC
Show Suggested Answer Hide Answer
Suggested Answer: B 🗳️
by [deleted] at May 10, 2021, 5:33 p.m.

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HungarianDish_111
Highly Voted 1 year, 9 months ago
Selected Answer: B
https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-7/High_Availability_DG.html#pgfId-44041 "When the HA pair is set up, by default, the Primary WLC's MAC address is synced as the Mobility MAC address on the Standby WLC" -> Devices in 5520 HA cluster already have the mobility mac. https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/config-guide/b_wl_16_10_cg/mobility.html "Ensure that you configure the mobility MAC address using the wireless mobility mac-address command for High-Availability to work" -> Mobility MAC needs to be set manually on new Catalyst 9800.
upvoted 12 times
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Ayman_B
Highly Voted 1 year, 10 months ago
Selected Answer: B
this allows the 9800 WLC to act as a "anchor" for client roaming, allowing clients to maintain their connection as they roam between access points that are controlled by different controllers and that will to remedy the issue
upvoted 6 times
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[Removed]
Most Recent 5 months, 1 week ago
Selected Answer: B
B is correct
upvoted 1 times
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supershysherlock
7 months, 2 weeks ago
Selected Answer: B
The mobility MAC on the 9800 WLC needs to match the 5520 HA cluster to maintain consistent mobility identity for seamless client roaming, especially during failover scenarios where the standby controller becomes active. This ensures uninterrupted mobility sessions as the controllers in the mobility group are recognized by a consistent MAC address.
upvoted 2 times
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Beehurls
8 months ago
Selected Answer: B
The 9800 needs both MACs for each cluster node. The 5520 cluster only needs one MAC for the 9800. The cluster nodes share the config so if one fails the other should still have the MAC for the 9800, but the 9800 may not have the other MAC for the secondary 5520.
upvoted 4 times
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[Removed]
1 year, 4 months ago
Selected Answer: B
The mobility MAC address is a unique identifier for a wireless controller in a mobility group2. A mobility group is a set of controllers that can share information and support seamless roaming for wireless clients1.
upvoted 3 times
[Removed]
1 year, 4 months ago
When using SSO (Stateful Switchover), the mobility MAC address of the active controller is used by both controllers in the HA pair2. This ensures that the mobility peers can communicate with the same MAC address regardless of which controller is active. In this scenario, the 5520 HA cluster already has a mobility MAC address configured, which is shared by both controllers in the cluster. However, the 9800 WLC does not have a mobility MAC address configured, which means it uses its own physical MAC address as the mobility identifier2.
upvoted 1 times
[Removed]
1 year, 4 months ago
When the primary 5520 WLC fails, the standby 5520 WLC takes over as the active controller and uses the same mobility MAC address as before. However, the 9800 WLC does not recognize this MAC address as its mobility peer, because it was expecting the physical MAC address of the primary 5520 WLC. Therefore, the mobility tunnel between the 5520 cluster and 9800 WLC breaks, and clients cannot roam without dropping their connection. To remedy this issue, we need to configure a mobility MAC address on the 9800 WLC using the wireless mobility mac-address command2. This will allow the 9800 WLC to use a consistent MAC address as its mobility identifier, and to recognize the mobility MAC address of the 5520 cluster as its peer. This way, the mobility tunnel will remain intact even after a failure on the primary 5520 WLC.
upvoted 1 times
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Gedson
1 year, 10 months ago
Selected Answer: A
Must be B
upvoted 2 times
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KOJJY
1 year, 11 months ago
Selected Answer: B
B CORRECT ANSWER
upvoted 1 times
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Stylar
1 year, 11 months ago
Selected Answer: B
To me B is correct. You have 2 5k devices with SSO, and a 1 9k device. If cluster and primary works fine, then everything is fine. However when Primary 5k device fails, secondary should take over. Now Secondary with 9k doesnt talk to each other as it should. Ensure that you configure the mobility MAC address using the wireless mobility mac-address command for HighAvailability to work. Therefore you should enable this on the 9k device so it knows about the other devices. Doing it on the cluster with already established SSO wont do anything. Given answer (B) should be the correct one.
upvoted 4 times
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fenilp1
1 year, 11 months ago
Selected Answer: A
A is correct. Things failed after Active 5520 went down and Standby took the Active role
upvoted 2 times
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zpacket
2 years ago
Selected Answer: B
Provided answer is correct "Once the HA pair is formed, the Mobility MAC cannot be changed or edited". https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-7/High_Availability_DG.html#pgfId-44041 That means that other mobility group members (in our case the newly added 9800 WLC) would have to make sure they are configured with the appropriate mobility mac of the existing 5520 cluster. There is NO possibility to change the HA MAC without breaking the HA and re-configure it. Seems there was a misconfiguration by the engineer who configured the new 9800 "to test new features".
upvoted 6 times
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Deu_Inder
2 years, 2 months ago
Correct me please if I am wrong here. The given answer is correct. Why? After stateful switchover, the standby 5520 will be active. As 'rlilewis' has quoted already, "The Primary units MAC should be used as Mobility MAC in the HA setup in order to form a mobility peer with another HA setup or **independent controller**" So, because after the switchover, the configured MAC address of the primary is no more valid, you need to change the MAC address on the 9800 controller to point it to the MAc address of the secondary.
upvoted 3 times
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Heim_Ox
2 years, 4 months ago
if mobility MAC wasn't already configured on the 9800, roaming wouldn't have worked. We are told it was working. I think the standby 5520 must have been the one that was forgotten to be configured. I would choose A.
upvoted 2 times
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winder
2 years, 4 months ago
Selected Answer: A
It is the roaming service between the new 5520 and the one 9800 not working (dropping). Seems to me that the new controller not forming a mobility peer with 9800 due to the new mac address of the device. that means there was no mac address sync on HA group of 5520. so A
upvoted 3 times
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rlilewis
2 years, 5 months ago
Selected Answer: A
No, A is correct. The question was quite clear that it was working fine until the 5520 failed over to the secondary node in its cluster. Why would configuring a mobility MAC on the standalone 9800 solve anything? High Availability (SSO) Deployment Guide: https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-7/High_Availability_DG.html "The Primary units MAC should be used as Mobility MAC in the HA setup in order to form a mobility peer with another HA setup or **independent controller**"
upvoted 5 times
alejaandrocd
2 years, 5 months ago
"In order to keep the mobility network stable without any manual intervention and in the event of failure or switchover, the back-and-forth concept of Mobility MAC has been introduced. When the HA pair is set up, by default, the Primary WLC's MAC address is synced as the Mobility MAC address on the Standby WLC which can be seen via the show redundancy summary command on both the controllers" Therefore, 100% should be configured on Cat98k
upvoted 2 times
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Beehurls
8 months ago
Because the 9800 must have only had the MAC of the failed 5520 while it was working and now that it is failed it is missing the MAC of the secondary 5520. The 5520 should only have one MAC for the 9800 so if it didn't have the MAC it would never have worked. Answer is B.
upvoted 1 times
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RhJ72
3 years, 2 months ago
https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/config-guide/b_wl_16_10_cg/mobility.html "Ensure that you configure the mobility MAC address using the wireless mobility mac-address command for High-Availability to work."
upvoted 2 times
timtgh
2 years, 5 months ago
But it's a SINGLE 98000, so it's not using HA. The 5520 side is the side with an HA cluster and needs the command.
upvoted 1 times
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[Removed]
3 years, 5 months ago
The given answer is correct
upvoted 2 times
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C (25%)
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