topic Re: Static Channel Selection and DFS Validation/Query about Timer Mess in Wireless

Static Channel Selection and DFS Validation/Query about Timer Messages

Erfan7 — Mon, 07 Mar 2022 06:04:48 GMT

Dear All I have 2 questions:

1. If I select a static/custom DFS channel of an AP, in that case, will the DFS protocol/mechanism work? and radio will stop using the channel for 30 minutes.

2. My second question is related to AP logs while discovery and join process, please let me know the meaning of following log messages, what is timer message and control message.

I. CAPWAP-3-ERRORLOG: Failed to handle timer message

II. CAPWAP-3-ERRORLOG: Failed to handle capwap control message from controller

Thanks.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

JPavonM — Mon, 07 Mar 2022 07:16:45 GMT

DFS detection under 802.11h standard is required for all APs certified to use DFS channels so it is mandatory whatever channel selection mechanism is used automatic or manual.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Scott Fella — Mon, 07 Mar 2022 07:40:34 GMT

Your second question can be answered by searching the error online. This will give you an idea of the various reasons that error would happen.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Erfan7 — Mon, 07 Mar 2022 07:50:16 GMT

JPavon I mean to say that, channel is fixed/static, not dynamic lets say 52,56 in 40MHz, and DFS mechanism is triggered, and AP radios stop transmitting for 30 minutes, and after that what will happen, because in custom settings channel is fixed and now how controller will assign a new channel after 60 seconds pause.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Erfan7 — Mon, 07 Mar 2022 07:56:51 GMT

Mr. Scott I just want to know what is "timer message" is that a heart beat related because I was getting while controller was pushing the new image into 2602i AP after joining, I'm curious about what actually relates, is that a capwap communication delay, heart beats etc.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

JPavonM — Mon, 07 Mar 2022 09:10:51 GMT

@Erfan7 AP do not stop broadcasting neither transmitting after a DFS event is detected.

After detection of DFS event the AP select a new channel on the DCA list, and broadcasts an 802.11h channel-switch announcement and disconnecct all stations.

If the new channel is not DFS the AP broadcast beacons and accept client associations.

If the new channel is DFS required the AP scan the channel for 60 secons and if it's free of any radar signal it broadcast beacons and accept clients, if there is a radar signal then selects another channel nad the process start again.

After 30 minutes the AP scan the channel where DFS event was detected to see if it's free from a new DFS event and if so, the channel change back to that channel announcing stations about the change for them to reconnect.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Erfan7 — Mon, 07 Mar 2022 10:05:42 GMT

Thanks to see your reply , but my question is still there, channel is already costumed and static on one channel, if this happens then why I cant see the channel change, let me tell you my experience, that happened when clients were frequently disconnecting from one AP, and I checked and found DFS triggered logs, I changed the dynamic channel and set the channel on non DFS channel, even though globally DFS was enabled on controller, after that nether disconnection observed and nor DFS triggered logs on that AP, and I often do this in the network, same thing happened when I made channel custom even on DFS channel.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Ann69 — Mon, 07 Mar 2022 10:27:22 GMT

@Erfan7 wrote: MyCCPay
Dear All I have 2 questions:
1. If I select a static/custom DFS channel of an AP, in that case, will the DFS protocol/mechanism work? and radio will stop using the channel for 30 minutes.

2. My second question is related to AP logs while discovery and join process, please let me know the meaning of following log messages, what is timer message and control message.
I. CAPWAP-3-ERRORLOG: Failed to handle timer message
II. CAPWAP-3-ERRORLOG: Failed to handle capwap control message from controller

Thanks.

See If the new channel is DFS required the AP scan the channel for 60 secons and if it's free of any radar signal it broadcast beacons and accept clients, if there is a radar signal then selects another channel nad the process start again.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Ambuj M — Mon, 07 Mar 2022 13:14:53 GMT

1. Correct

2. both are generic messages on AP indicating AP was not able to join the controller, can be timer issue, can be country mismatch.

you want to post the debug logs from controller side to find the actual reason for AP not establish capwap tunnel.

share debug capwap event enable and debug capwap error enable and debug pm PKI enable.

use debug disable—all to disable the debugs.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Erfan7 — Mon, 07 Mar 2022 13:58:19 GMT

Sorry to say Jpovan, but please no need to hast, I said AP was joined while it was downloading the image from controller, I was getting these log messages "failed to handle the timer message" during download, once download completed AP got rebooted and successfully joined the controller..

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Scott Fella — Mon, 07 Mar 2022 14:49:37 GMT

I’m assuming you got your answer about the DFS as that was explained pretty well by @Japovan. As far as any messages you see and wanting to know what it means, an internet search is your best tool. That is exactly what we do to provide questions about anything related to “what does this mean”. It’s the same if you asked, “my ap doesn’t join and here is the output”, and we see specific messages. There are also tools that Cisco provides that can help you analyze debugs or review your configurations. If you are new to Cisco wireless, that is also a good start.

https://developer.cisco.com/docs/wireless-troubleshooting-tools/#!wireless-troubleshooting-tools/wireless-troubleshooting-tools

https://www.cisco.com/c/en/us/support/web/tools-catalog.html

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Erfan7 — Mon, 07 Mar 2022 18:27:38 GMT

Mr Scott I first searched on internet, then I came on this forum, Japovan shared the same detail as on cisco websites, I already knew DFS details, the question I asked no body answered, I dont wanna know the DFS theory, infact I cudnt find the answers of both questions on internet, thats why I came here, anyhow thanks for your time.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Scott Fella — Mon, 07 Mar 2022 18:38:28 GMT

It's not a theory, it's a mandatory DFS requirement. Why not ask you question again in more detail, because to me, your questions have been answered.

If your AP was joining, why would you even bother looking at the logs. If the AP joins and you are not having any issues, don't worry about anything. If you can't find a Cisco documented link with what the errors mean, then only TAC would know that info. That would be your next step if you go that route.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Erfan7 — Tue, 08 Mar 2022 09:00:28 GMT

Scott my word theory mean DFS working principle, I know its mandatory thats why asked this, if I select a DFS channel manually, lets say on 100,104 channel and due to some pulse, DFS triggers, then what will happen...because i have done this I customized the channel and after that I didnt see any DFS trigger logs, that means if you manually set the channel , DFS will not shift the channel, and one more thing I cudnt see any thing in this regard in cisco articles.

2nd thing was so simple I was digging out the error messages and their possible explanations, and this message was out of that about which I cudnt find any explanation or reason in cisco articles or on internet, and I wasnt worry just I was curious.

Thank You Scott

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Scott Fella — Tue, 08 Mar 2022 10:15:37 GMT

When there is a DFS detection, the ap will disassociate clients, stop the radio for the specified time. So since you have set a static channel, that will not change. So until the radio detects no radar for at least 60 seconds, then the radio will start associating clients. As for your other question, open a TAC case.

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

Erfan7 — Tue, 08 Mar 2022 10:27:56 GMT

Scott you mean channel will be changed after radar detection, and as per DFS algorithm previous channel will be black listed and after 60 seconds of scanning AP will be assigned interference free channel..

But again I would must say channel is fixed, and I have not observed channel shift once I made that static...and this is the thing I want to understand, that in static channel scenario, will the DFS shift overruled...That I have observed too

One more thing in that period DFS detects didnt stop because if I make it dynamic I see the triggers logs again....

Re: Static Channel Selection and DFS Validation/Query about Timer Mess

JPavonM — Tue, 08 Mar 2022 12:53:29 GMT

@Erfan7how do you know there is a DFS event that should be triggering a channel shift on the AP? Do you mean you're seen such DFS event in AP logs and an AP channel shift is not happening? If this is your scenario, you should open a TAC case as DFS is mandatory. If the AP is not leaving that channel after a RADAR signal is detected, then that could be a defect that needs to be analysed and fixed, otherwise you could be fined.