topic Re: Access points stop braodcasting SSIDs in Wireless

Access points stop braodcasting SSIDs

TrickTrick — Thu, 24 Oct 2024 13:35:59 GMT

Hi everyone,

I noticed in new deployment 9800-L deployment, that a lot of Access points stop randomly broadcasting SSIDs.

I analyzed the config by using the Wireless Config Analyzer tool, and noticed :

RF: WLC has 84.6% of APs with failed Interference Profile for 2.4GHz Band

RF: WLC has 25.0% of APs with high channel utilization for 2.4GHz Band

When I reboot those APs (because not all of them are affected), they work normally for about 2 days (more or less than that) and stop broadcasting again.

I'm suspecting the RF interferences as per the warnings displayed in the analyzer tool. Took a look on DCA parameters in the 2.4Ghz band, and changed the "DCA Channel Sensitivity" to high, it was medium by default. The APs are probably too close to each other, I'm trying to understand first if this is the reason why the SSIDs are not broadcasted.

Any suggestions beside of that ? should I enable more channels within the channels list ?

Thank you in advance

Re: Access points stop braodcasting SSIDs

Mark Elsen — Thu, 24 Oct 2024 13:52:58 GMT

- You can also specify a syslog server for the APs in the AP Join Profile. This may help to get extra insights.

Go for a recent release , 17.12.3 is recommended.

Look at this document : https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9800-series-wireless-controllers/217738-monitor-catalyst-9800-kpis-key-performa.html

Use the links for AP kpis and RF stats for further analysis,

Re: Access points stop braodcasting SSIDs

TrickTrick — Thu, 24 Oct 2024 15:49:52 GMT

Strange enough, a lot of APs appear in monitor mode:

AP Name Mac Address Slot Admin State Oper State Width Txpwr Channel Mode

AP100_Basement 70bc.55h7.45cf 0 Enabled Up N/A N/A N/A Monitor

What is more strange, is that some of those are working properly, while those which appear to be normal, are not broadcasting SSIDs

Re: Access points stop braodcasting SSIDs

RxTx — Thu, 24 Oct 2024 16:25:59 GMT

This is because you have active FRA - check Flexible Radio Assignment Configuration and disable Flexible Radio Assignment and switch back every AP as you want.

Re: Access points stop braodcasting SSIDs

TrickTrick — Thu, 24 Oct 2024 16:56:58 GMT

Hi,

I'm trying to understand why this is happening ( a lot in monitor mode)
I did btw disable that for 2.4Ghz but still in Monitor Mode

Re: Access points stop braodcasting SSIDs

RxTx — Thu, 24 Oct 2024 17:13:05 GMT

Probably WLC sw decided ( when FRA was enabled ) that 2.4Ghz it is not usable because of RF interference or another reason from configuration parameters and changed the AP's to ignore 2.4Ghz/monitor mode.

If FRA it is disabled now, every AP that was switched to Monitor or have RF 2.4Ghz disabled will remain in that state until it is manual changed to a desired state - enabled.

Re: Access points stop braodcasting SSIDs

Mark Elsen — Thu, 24 Oct 2024 17:13:26 GMT

- FYI : https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwi74744

Re: Access points stop braodcasting SSIDs

Flavio Miranda — Thu, 24 Oct 2024 17:19:47 GMT

@TrickTrick

No, WLC does not stop advertising SSID because interference. That´s for sure. The problem is something else. It can be bug, most probably it is.

One situation I can imagine and I went through this in the past is, someone have a wireless network near by and is attacking you. This cause the SSID to desapear from the machines from time to time because the other WLC is sending deauthentication to your clients.

Usually Meraki does that very often depending on how it is configured. On my case, it was a Meraki gear. But, other vendors, cisco inclusive, have this feature.

One more situation I can come up with is, authentication issue. If the client fail to authanticate too often, the operational system can black list the SSID causing it to desapear from the SSID list. Keep this also in mind.

Re: Access points stop braodcasting SSIDs

Leo Laohoo — Thu, 24 Oct 2024 21:27:19 GMT

What models of APs is this behaviour evident? Are they 2800/3800/4800/1560 or Catalyst 9k APs?

Re: Access points stop braodcasting SSIDs

TrickTrick — Fri, 25 Oct 2024 08:46:34 GMT

9K APs, 9162

Re: Access points stop braodcasting SSIDs

Leo Laohoo — Fri, 25 Oct 2024 08:58:40 GMT

Reboot the APs and see if this improves.

If this improves, make it a point to regularly reboot the APs.

If the switches are Cisco, I have an EnergyWise config that can shut/unshut PoE in a schedule.

Re: Access points stop braodcasting SSIDs

Rich R — Sun, 03 Nov 2024 12:56:36 GMT

You've not once mentioned what version of software you're using @TrickTrick ?
Refer to TAC recommended link below.

As RxTx and others have said FRA will change AP mode but disabling FRA will not change back the APs which were changed by FRA - you need to change them back manually.

And as Flavio pointed out even if channel utilisation is high the AP should not stop broadcasting the SSID if it is enabled - that is always going to be a software bug. There have recently been a number of bugs relating to APs incorrectly reporting high channel utilisation too so it is very important to make sure your software is up to date. Even a containment attack (eg from neighbouring Meraki network) will not stop the APs broadcasting - it will just stop clients from associating.

Re: Access points stop braodcasting SSIDs

Ruan Jansen — Wed, 14 Jan 2026 01:34:17 GMT

Hi @TrickTrick

Did you manage to get a solution for this?

Re: Access points stop braodcasting SSIDs

Rich R — Wed, 14 Jan 2026 12:03:27 GMT

Hi @Ruan Jansen you are replying to an 18 month old post - there have been dozens of software releases and bug fixes since then. If you are experiencing a similar issue best to open a new thread with full and complete details of the exact scenario you have encountered. Remember to include:
- Exact details of observed problem. Is it cleared by AP CAPWAP restart? Is it cleared by AP radio shut/no shut? Is it cleared by AP reload? Is it cleared by WLC reload (or switchover if HA-SSO)?
- Software version(s) (including applied SMUs and APSP)
- WLC model(s)?
- AP model(s)?
- Which radios are affected? 2.4, 5 or 6 (or all)?
- WLAN configuration (including flex/central switching etc)?
- AP mode (flex/local)?
- What troubleshooting and debugs have been done and what has that shown?

Re: Access points stop braodcasting SSIDs

TrickTrick — Thu, 15 Jan 2026 09:28:04 GMT

Hi Ruan,

I fixed this back then by upgrading to another release (even though it was the recommended one I was using, it was affected too).

I switched all the APs to Client mode manually instead of automatic in the meantime. But the upgrade if I remember well has fixed the issue.