WLC 5508 Master controller software upgrade

[mike.ru23]

Hello

I have 3 WLC's and want to get the master controller upgraded to a newer version, but do not want to effect the other 2 WLC's. Is this possible? 

5508: 8.0.120.0 Master Controller; controlling AIR-CAP2702I-A-K9

2504(1): 8.0.120.0 controlling AIR-LAP1042N-A-K9, AIR-LAP1142N-A-K9, AIR-LAP1131AG-A-K9

2504(2): 7.6.130.0 controlling AIR-LAP1042N-A-K9, AIR-LAP1142N-A-K9, AIR-LAP1131AG-A-K9

The 5508 is the master controller. I want to upgrade it to 8.5.160.0 and not effect the others because they are controlling older AP's. The goal is to get the 5508 upgraded and deploy newer 2808i AP's and start to phase the older ones out, but we cannot have any downtime. 

Will sending the software upgrade to the 5508 effect the software versions of either of the 2-2504s?

Thanks in advance for your time!

[balaji.bandi]

Not sure what is the use case here, when you deploy High availability the code should be the same to maintain all over.

If you are testing any other purpose, instead you can do secondary to test WLC before upgrade to production one.

[mike.ru23]

I apologize, but I'm not sure what your mean by the code.

[Leo Laohoo]

Read the Release Notes very, very carefully.
It is not possible to upgrade from 8.0.X.X (and earlier) to 8.5MR6 directly without going through an intermediate version, 8.2.16X.X.

[Scott Fella]

You don’t really have enough info. When you upgrade the code, there will always be a downtime when the AP’s reload. So if you want to reduce your downtime, the best if if you don’t have any AP’s on the 5508 and then remove the 5508 as a primary or secondary controller. You would upgrade, by following the release notes like Leo mentioned. Once the 5508 is upgraded to the code you want, then you add new AP’s or move existing by setting the high availability on each ap. Again, the ap will reload anf you will have a downtime. There are other ways where you can pre-download the image to AP’s, but you have to upload the image and then push it out to the ap. I’m your case, you have a double upgrade which you need to account for.

[Leo Laohoo]

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@Scott Fella wrote:
I’m your case, you have a double upgrade which you need to account for.

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Totally forgot about the "double upgrade" event.  After the exercise we did (just last week), this takes about 25 minutes (per AP).