topic Re: Cisco 2802 AP not transmitting on 2.4GHz in Wireless

Cisco 2802 AP not transmitting on 2.4GHz

scottbreslin — Sat, 27 Jul 2024 08:28:32 GMT

Hi,

We have a customer network with 20 2802 series APs operating in FlexConnect mode on a 3504 WLC running SW 8.10.156.0

However, only 8 of them are transmitting on their 2.4Ghz interfaces even though the the interfaces are up and the SSIDs are configured to broadcast on these frequencies. The following screen shots further depict this behaviour:

All 20 APs:

APs Filtered by 802.11 b/g/n:

Example AP not broadcasting on 2.4Ghz but with interface UP:

The APs are none client serving and not in monitor mode. They have also been rebooted with no resolution

Does any one know why 12 of the 20 APs are operating in this way and also how to resolve the issue.

Thanks

Re: Cisco 2802 AP not transmitting on 2.4GHz

Mark Elsen — Sat, 27 Jul 2024 08:43:06 GMT

- Have a checkup of the 3504 WLC configuration using : WirelessAnalyzer input (procedure) for AireOs controllers
and feed the output from that into Wireless Config Analyzer

- Upgrade to the last/latest advisory software version = https://software.cisco.com/download/home/286312601/type/280926587/release/8.10.196.0
the reason being that besides possible bug related issues the aireos platforms are being phased out and consider it
kind of mandatory to use the last release available for a particular model ,

Re: Cisco 2802 AP not transmitting on 2.4GHz

Mark Elsen — Sat, 27 Jul 2024 10:51:38 GMT

- Added reply : + could you also check the POE status on the switchport for the involved APs , (check if sufficient power is provided to the AP)
+ Another way to check this or other issues ; to power cycle the AP (when POE is used that is easy accomplished by shutting the port and no-shut afterwards). Then immediately after the AP has booted login to it and issue the command show logging (at that time most of the boot log is still available) => Look for errors if any (e.g.)

+ In the same context you may also want to configure a syslog server for the APs as in :

config ap logging syslog facility all
config ap logging syslog level 6 all
config ap syslog host global x.x.x.x (x.x.x.x being the ip address of the syslog server)

For more info on these commands checkout : https://www.cisco.com/c/en/us/support/docs/wireless/4100-series-wireless-lan-controllers/107252-WLC-Syslog-Server.html

Re: Cisco 2802 AP not transmitting on 2.4GHz

RxTx — Sat, 27 Jul 2024 11:30:21 GMT

Hi,

Check Radio Role Assignment if it is in Auto change to Manual as in my pic:

edit: Also check what HW version are the AP's.

Re: Cisco 2802 AP not transmitting on 2.4GHz

Flavio Miranda — Sat, 27 Jul 2024 16:48:56 GMT

Hi @scottbreslin

They are on the same AP group and advertising the same SSID?

Re: Cisco 2802 AP not transmitting on 2.4GHz

scottbreslin — Sat, 27 Jul 2024 17:41:15 GMT

Hi yes and same flexconnext group. It's like some sort of glitch.

Re: Cisco 2802 AP not transmitting on 2.4GHz

Flavio Miranda — Sat, 27 Jul 2024 17:46:42 GMT

I asked because it could be advertising different SSID and you have the possibility of disable 2.4 on per WLAN basis. And, you could have the same SSID with different Wireless profile on different AP group. Noticed, not fiexconnect group but AP group.

But, if they are advertising the very same SSID and they on the same AP group then you might be hitting a bug.

Re: Cisco 2802 AP not transmitting on 2.4GHz

scottbreslin — Sat, 27 Jul 2024 19:10:05 GMT

Hi,

Thank you for the reply. I'm not able to see the APs in the list of available units under the 802.11bgn list in order to be able to change the mode. They APs are just not showing.

Re: Cisco 2802 AP not transmitting on 2.4GHz

RxTx — Sat, 27 Jul 2024 19:35:52 GMT

Hi,

Can you ssh on problem AP and post result of:
show controllers dot11Radio 0

and

show lldp inline_power

Re: Cisco 2802 AP not transmitting on 2.4GHz

Mark Elsen — Sun, 28 Jul 2024 04:43:59 GMT

>...Hi yes and same flexconnext group. It's like some sort of glitch.
- So , upgrade to https://software.cisco.com/download/home/286312601/type/280926587/release/8.10.196.0
and check if that can help ,

Re: Cisco 2802 AP not transmitting on 2.4GHz

scottbreslin — Sun, 28 Jul 2024 07:36:05 GMT

Hi – I do not have ssh access to customer environment for these APs, only GUI access to WLC. Therefore, I will need to ask customer to provide the output and report back. Thank you for the support 😊

Re: Cisco 2802 AP not transmitting on 2.4GHz

RxTx — Sun, 28 Jul 2024 07:48:16 GMT

Hi,

Any chance for you to try and reboot one problem AP from GUI interface and check the Radio 0 settings after that ?

Re: Cisco 2802 AP not transmitting on 2.4GHz

scottbreslin — Sun, 28 Jul 2024 07:54:05 GMT

All problem APs have been rebooted with same issue once rejoining.
I have also moved one prob APs to backup WLC (same model and SW) and same issue is seen on this WLC also.

Re: Cisco 2802 AP not transmitting on 2.4GHz

RxTx — Sun, 28 Jul 2024 08:36:01 GMT

Then I see two possibility you have to investigate:

- HW failure big chances if AP worked in high temperature environment or are HW 1 & 2 and also switch/injector PoE problems.

- also check if Flexible Radio Assignment Configuration it is Disabled if customer want to use 2.4 Radio and if it is possible to upgrade controller to latest recommended version.

edit:

-best if somebody can test one problem AP in another environment after full reset: test (v)WLC or latest ME sw

Re: Cisco 2802 AP not transmitting on 2.4GHz

scottbreslin — Sun, 28 Jul 2024 09:22:03 GMT

I appeared to have resolved the issues.

It was a strange issue. As I understand the APs have 2 radios and by default slot 0 is 2.4Ghz and Slot 1 is 5Ghz so a correctly operating AP such as the one below, has 0 for 2.4Ghz and 1 for 5Ghz

However, on the APs with issues, Slot 0 was being used on the 5Ghz.

To resolve the issue, this is what I did:

To avoid affecting the production WLC I moved an AP over to the backup WLC. Then went into the radio properties of slot 0, set the Admin mode to disable and the mode to manual/client serving. This then changed the band to 2.4ghz. Finally, I then set the Role back to auto/client serving.

Moved the test AP back to the production WLC and the repeated the above steps on the remaining 11 APs

Will monitor this over the next couple of days to see if the behaviour changes.

Thank you all so much for all the technical input on this issue 🙂

Scott

Re: Cisco 2802 AP not transmitting on 2.4GHz

RxTx — Sun, 28 Jul 2024 09:51:10 GMT

On 2802/3802 Radio 0 it is dualband 2.4Ghz/5Ghz.

Because you have Flexible Radio Assignment Configuration - Enabled controller will auto change dual band Radio 0 to what he thinks it is best 2.4Ghz or 5Ghz ( if no 2.4 clients are registered on AP).

If you don't need that behavior you have to disable Flexible Radio Assignment Configuration or assign manual Radio 0 on all AP's as instructed in first replies with images.

Re: Cisco 2802 AP not transmitting on 2.4GHz

scottbreslin — Sun, 28 Jul 2024 09:50:05 GMT

FRA is disabled.

This is why it was strange issue.

FRA has never been enabled.

Re: Cisco 2802 AP not transmitting on 2.4GHz

RxTx — Sun, 28 Jul 2024 10:10:57 GMT

In your case the AP's with Radio 0 were set to Monitor Mode so that is the cause it was not transmitting on 2.4GHz as appearing on last pic.

Not sure if that is a bug or it was set as intended by somebody.