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9800 CLI/SSH wireless show command output slow


Output of wireless related show commands like 'show wireless client summary detail', 'show ap dot11 5ghz summary', or 'show ap summary' on the 9800 CLI is very slow. It takes ~42 seconds to display data on ~2700 clients on a 9800-40 if you disable paging. This has been the case in 17.3, 17.6, and 17.9.

On the 5520 controller on any AireOS version >= 8.5 'show ap summary', 'show client summary', or 'show advanced 802.11a summary' only takes a couple of seconds at most to output around the same amount of clients and APs. I'm only noticing this because we're running wireless controllers with >=1000 APs and >=2700 clients. 

Something is happening on the 9800 in all IOS XE versions that is causing a big performance hit to SSH output of wireless data which makes it very annoying to verify operational parameters for example.

I don't really have time to open a TAC case on this one, but this issue should be extremely easy to reproduce in a lab environment. Someone at Cisco with a lab environment should really spin up some virtual APs and clients and test it - it's a pretty big performance decrease going from 5520 to 9800 which is not what we want to see for a new flagship product I would expect.



7 Replies 7

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             >...Someone at Cisco with a lab environment should really spin up some virtual APs and clients and test it

 This forum is not populated by Cisco employees but by customers, to get that kind of  commitment from Cisco you need to create a ticket (TAC). For the time being  have a health  checkup of the 9800 configuration with the CLI command : show  tech   wireless , have the output analyzed by  , please note do not use classical show tech-support (short version) , use the command denoted in green for Wireless Analyzer.               Checkout all advisories!


Rasika Nayanajith
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By any chance all those 1000AP manage by a single WNCd of that controllers or are they distributed among 5x WNCds using different site tag values. 
I got 300AP (9800-80) & did not see any such delays.


There are 1000 APs across 66 site tags, it's set up with a site tag being used for the set of APs belonging to each building.

I also have a 9800-80 that we're in the progress of migrating to with 8 site tags, 132 APs, and 302 clients (at this moment)  if I do "term len 0" on that one and "show wireless client summary"  it takes ~4 sec to output the list of 302 clients. On AireOS that would take something like 100ms.

It's the kind of thing that's more annoying than impeding, so that's the reason why I've just posted here for now. I'm fine with just waiting for successive IOS XE releases to fix it at some point.



                 - Remember to use WirelessAnalyzer (as per my initial reply)  , very informative


Scott Fella
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If this is a problem and others are not seeing this, you should open a TAC case.  I don't think future versions will fix your issue if its not a reported issue/bug.  Can be something else that might be causing this for you.

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Rich R
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9800-80 with 861 APs and 1573 clients - just tested:
APs about 9-10 seconds
Clients about 6 seconds.
So agreed it may be slightly slower than AireOS but not a problem for us.
Worth checking you have TCP tuned properly in IOS?  What works best will depend on your environment but look at ip tcp mss <> - sized to ensure no fragmentation will be required, ip tcp selective-ack, ip tcp window-size 65535 and ip ssh window-size 65535.  Note there seems to be a bug with scp download of large files *from* the device which hang at 99% when window is 65535 - in that case reducing to 32768 works.  I've never got round to testing the breakpoint or opening a TAC case for it though.  Uploading files to the device is not affected though.

I think you actually reproduced the problem if you were testing with "show ap summary" and "show wireless client summary". Our results almost the same when looking at it in terms of ratios of output time/ap or output time/client if those commands were used.

I just tested again and the output of "show ap summary" is ~14sec for 999 APs and the output of "show wireless client summary" is ~18sec for 4086 clients.

The ~40 sec at or so time I gave above was for "show wireless client summary detail", and indeed if I run that command on my WLC with the current client count of ~4086 it takes ~65sec. 

"show ap dot11 5ghz summary" for 999 APs is ~27sec for me.

All non-wireless-related SSH output from the WLC is not affected. The problem looks to be a performance issue internal to the WLC, especially since wireless show commands that return more data seem to take a lot more time for the same number of APs and clients.


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