An engineer is trying to determine the most cost-effective way to deploy high availability for a campus enterprise wireless network that currently leverages three wireless LAN controllers. Which architecture should the engineer deploy?
I think it must be answer B
Access Point Stateful Switch Over (AP SSO) functionality is not supported for N+1 HA.
Source: https://www.cisco.com/c/en/us/td/docs/wireless/technology/hi_avail/N1_High_Availability_Deployment_Guide/N1_HA_Overview.html
I think it might be D
The Problem I have with answer B is that the question says "leverages three wireless LAN controllers".
N+1 without SSO would just be 2 x WLC's (one primary & the other Secondary).
You would need N+N+1 (Chapter9: Designing High Availability - page 199) to achieve HA with 3 controllers and no SSO Involved.
So logically the only right answer would be D (the first two "N" WLC's in an HA/SSO pair with the "+ 1" tertiary WLC as the backup). Capwap tunnels would remain in SSO between the HA/SSO pair but would naturally have to be rebuilt if the HA/SSO pair failed and the AP's moved across to the tertiary "+1" controller.
Credit where credit is due, these CCIE's that cisco pay to write these exam questions know how to make them tricky :)
I think you are right. From Cisco Elearning Training:
When there are many Cisco WLC devices and capital expenditure costs are a significant consideration, a controller redundancy design N+1 solution is an option.
In this configuration, each AP is configured for its primary controller, and all APs are configured to fall back to a common secondary.
They are talking about N+1 HA with HA-SKU which allows to provide backup for multiple primary WLCs. look the diagram.
SSO should be configured as primary
a third controller should be configures as secondary
This falls on N+1 , where N represents some number of active controllers and 1 denotes the one backup controller.
Also look at the book, chapter 9 page 200
"Because each active controller has its own hot standby controller, there really is no need to configure a secondary or tertiary controller on the APs unless you need an additional layer of redundancy."
I think 2 WLC 's forming SSO needs to ne identical, in the question nothing about type of WLC's , so I think B must be, from the other side practically I prefer more D
Everyone agrees it comes down to either "B" or "D".
IMO, the answer is B. This is simply because SSO is considered N+N from a documentation standpoint (meaning every site needs to have TWO wlcs), making "D" technically a non existent thing. If one of the answers was "N+N+1", I would actually consider that as the correct answer, but that isn't one of the options.
https://www.cisco.com/c/dam/en/us/td/docs/wireless/controller/9800/17-1/deployment-guide/c9800-ha-sso-deployment-guide-rel-17-1.pdf
On 9800s it is supported and on 5500 it is not
It is D
https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-1/Enterprise-Mobility-8-1-Design-Guide/Enterprise_Mobility_8-1_Deployment_Guide/cuwn.html#:~:text=Right%20to%20Use)-,High%20Availability,-N%2B1
I agreed with B
https://www.cisco.com/c/en/us/td/docs/wireless/technology/hi_avail/N1_High_Availability_Deployment_Guide.pdf
The scenario is N+1 with HA = 3 WLC's
N = #1 Primary
+1 = #2 Primary
HA = Backup
In the N+1 HA redundancy model, one WLC serves as the backup controller for N primary
controllers. When any of the primary WLCs fail, the APs connected to that controller fall back to the backup controller.
SSO = Access Point Stateful Switch Over (AP SSO) this functionality is not supported for N+1 HA. The AP Control and Provisioning of Wireless Access Points (CAPWAP) state machine is restarted when the primary controller fails
The answer is D. With n+1 with sso you don't have to buy extra license as when the primary fail everything is moved to the second one without much effor.
Answer is B, as the following deployment guide explicitly says SSO is not supported with N+1 HA
https://www.cisco.com/c/en/us/td/docs/wireless/technology/hi_avail/N1_High_Availability_Deployment_Guide/N1_HA_Overview.html
"Access Point Stateful Switch Over (AP SSO) functionality is not supported for N+1 HA. The AP Control and Provisioning of Wireless Access Points (CAPWAP) state machine is restarted when the primary controller fails."
D is Correct.
HA (that is, AP SSO) can be deployed with Secondary and Tertiary Controllers just like today. Both Active and Standby WLCs combined in the HA setup should be configured as primary WLC. Only on failure of both Active and Standby WLCs in the HA setup will the APs fall back to Secondary and further to Tertiary WLCs.
Check this Section "SSO Deployment with Legacy Primary/Secondary/Tertiary HA"
https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-7/High_Availability_DG.html
N means Active , while 1 is backup.
Primary controller should be SSO Controllers (pair of WLC)
Secondary controller sholud be a single controller
B - The questions states 'most cost-effective', N+N is not cost-effective, all the documentation says it is an 'extremely expensive solution, so it has to be one of the N+1 options to meet this requirement. I can't find anything to say you can deploy N+1 with SSO, so that only leaves B.
disagree I found a community that discusses using 1+1, N+1 with SSO. so for me the answer is correct D. https://community.cisco.com/t5/wireless/n-1-or-1-1-with-client-sso/td-p/3339846
https://networkguy.de/cisco-wlc-high-availability/
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