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Software suggestion for 8540 WLC with mix of legacy and cos ap's


We are running several sites with 8540 WLC and a mix of legacy and up to date AP's

Currently we run AireOS on all WLC's but we have had issues, especially with the 2800 ap's and false radar detection.

According to the release notes we shouldn't have these issues, but reallity prevails.

Here is a summary of our issues today:

  • Problem med false radar detaction, making APs jump to non dfs channels (channel 36 - 64). 
  • AP's dropping CAPWAP sessionen with WLC, only partial session established. (spurious instances)
  • AP's generating error log messages on duplex mismatch. 

In the TAC recommended releses should be the obvious choice, but only one site has a range of access points that supports Also I have seen some really nasty bug notices lately on the release.


In the light of above information; should anyone recommend relese, or should the be sufficient?

I cannot find anything in the regarding false radar detection that isn't fixed already in

...but does have two bug IDs (CSCvf38154, CSCvf21657) that isn't noted in the release notes.


Any suggestion and advice are welcome.


Sincere Regards

Hall of Fame Community Legend

I am still stuck with

Hi Leo.


Any reason why you haven't upgraded?

From which code did you upgrade to

I have learnt from others that train will improve roaming performance compared with


What is your inpu?t

Hall of Fame Community Legend

Upgraded from
Didn't go any further because we haven't seen anything so scary that warrant an outage due to an upgrade.
VIP Advocate

Happily running here since several months.
As you are having issue, you could also consider ESCALATION build, which fixes a few additional bugs and is the last of the 8.3 train. There will (probably) come no more updates for 8.3.
More info:



Appreciate the advice.

We will consider that or wait until a new maintenance release is release för 8.5 train. You are aware of this field notice?

Other nastyness; CSCvg83600, CSCvt47413, CSCvt98797 et cetera.

Of course there are an Escalation release available for 8.5 as well, but the latest notifications suggest more work is needen on 8.5...



Mats note that FN70577 does NOT affect
We've been running since shortly after release across 6 HA-SSO pairs + 5 other single WLC with around 12000 APs and it's been very stable.



It says so in the field notice:

Affected Version Upgrade to this Version Comments

AireOS through or laterAireOS 8.5 MR6 Escalation, available from the Technical Assistance Center (TAC)
AireOS or later 
AireOS through, or laterAireOS is available from the TAC
AireOS or later 
AireOS through or laterAireOS 8.10 MR2 Escalation, available from theTAC
Cisco IOS XE 17.1.1sCisco IOS XE 17.1.1tFor 9800 and EWC-AP
Cisco IOS XE 17.1.1sCisco IOS XE 17.1.1s ESFor Embedded Wireless Controller on switches
Cisco IOS XE 17.2.1Cisco IOS XE 17.2.1a 

Indeed, it looks like the bug was introduced in and fixed again in


No Mats - read carefully - is NOT in the Affected Version list. We confirmed this with TAC.
The bug was introduced in as PAT pointed out below and that is what the FN says.
It was discovered and fixed again very quickly.

There is always more work needed. Often the bugs also affect various older versions, but will not anymore listed, because they're out of support.
If your APs all support 8.5, then I'd go for 8.5.
The linked bugs all sound like the same issue (the later two), but nothing that would worry me much indoors. Of course, if you are operating inside an airport, than this might be an issue.
Hall of Fame Master

You should provide us with what ap models you have, so we can help you with options on image. Don’t look too deep into all the bug’s or else you will never find an image. There is the TAC preferred image site: <> and then there is the matrix that shows what devices are supported with what image: <>.
Also look at it this way, you can always upgrade a site to a different version since it has newer ap’s or controllers, you always don’t have to stick to the same image for consistency, especially if you can’t upgrade site fast enough to migrate to what you want.
This is important, you discover what issues you are having and then you look for a remediation plan, which is your code, and then resolve that issue. When you don’t resolve issues fast enough, then the user experience suffers and they will always say the wireless sucks. Do one site at a time, kind of like a pilot and make sure the experience is better for the users before you start upgrading/downgrading other sites. Always look for feedback from the users, because what is documented in the release notes, is know and documented bugs, but you can always have poor performance with a specific image, ap type, or even controller type or feature that your have enabled.
*** Please rate helpful posts ***

Hi Scott.

Thank you for your insights. Actually I have gotten feedback that the oldest legacy ap's have been replaced, so now we have a mix of mostly 2800. with a lower count of 2700 and 3500 series access points on the controllers in question. These are all supported in 8.5 tree. I am pretty sure that our best candidate is or if a later maintenance release is provided. It will surely improve roaming performance if feedback from collegues are correct. Or should you recommend that we make a request for the 8.5.161.x Escalation release?






Hall of Fame Community Legend

No, that's not correct. 3500 is supported up to 8.4.X.X.


Hi Leo

At least on the WLC 5520 the 3500 is still supported in 8.5.