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  • 1.  Cannels 120, 124 & 128 on 5GHz

    Posted Feb 08, 2023 09:44 AM
    Hi all,

    We have couple of clusters with VC. I need to use channels 120-128, however from what I read the APs check for radar systems for 10 minutes after first initiated and then for 10 minutes every 24 hours.
    Question 1 - Can anyone confirm or deny it?
    Question 2 - Is there a way to control when the APs stop working to check for 10 minutes? If not is there a way to check when they will do it?

    We are UK based if that matters.

    Thanks,
    David


  • 2.  RE: Cannels 120, 124 & 128 on 5GHz

    Posted Feb 08, 2023 05:52 PM

    check this zero wait DFS feature that i think it was part of firmware 8.8

    https://www.arubanetworks.com/techdocs/Instant_810_WebHelp/Content/instant-ug/arm/zero-wait-dfs.htm



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  • 3.  RE: Cannels 120, 124 & 128 on 5GHz

    Posted Feb 09, 2023 09:55 AM
    I don't believe DFS channel changes should really have to be disruptive.
    When the access point detects radar activity, it can announce to the
    clients that it is going to switch to a new channel so they switch at
    the same time.

    Interesting observation here, my Cisco 2702 access points always
    detected radar activity at various DFS channels, so I could only use a
    small subset of the 5 GHz band. I am fairly sure there is no kind of any
    radar nearby. My new Aruba access points don't find any radar activity.

    It would be nice though to have a way to see if DFS scanning is taking
    place. Now when I change a channel, I spend "some time" waiting for the
    SSID to appear. I can't find any logging or command output that tells me
    this.


    Original Message


  • 4.  RE: Cannels 120, 124 & 128 on 5GHz

    Posted Feb 10, 2023 03:52 AM

    I'm not aware with the point that APs will go down for 10 minutes every 24 hours; the radar detection has to happen continuous when the radio is operational as a (near to) immediate response to go off-channel is required to avoid further interference with radar systems. 

    Do you actually see this happening? Or are you just reading and would like to understand?

    If you see APs go down every 24 hours, please work with your Aruba partner or Aruba Support as that doesn't look correct. Note that channels 120-128 are known to have active radars and in many deployments are excluded from the channel plan. So if these are the only channels you can use, there may be unexpected responses.



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    Herman Robers
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    If you have urgent issues, always contact your Aruba partner, distributor, or Aruba TAC Support. Check https://www.arubanetworks.com/support-services/contact-support/ for how to contact Aruba TAC. Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.

    In case your problem is solved, please invest the time to post a follow-up with the information on how you solved it. Others can benefit from that.
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  • 5.  RE: Cannels 120, 124 & 128 on 5GHz

    Posted Feb 13, 2023 03:38 AM

    Hi David,

    Channels 52 - 144 are all potentially DFS but 120-128 are weather radar specifically. I have only had an issue with DFS once during a Wi-Fi AP0aS survey, I was using fixed channel and power on channel 100 and lost 5GHz for 30 min's (Consoled onto the AP 2702 which confirmed DFS detection). I guess if I was using dynamic channel it would have just dropped me and then re authenticated to another channel more or less immediately. The AP's should just gracefully move clients onto another free channel when detected without too much issue.


    Original Message


  • 6.  RE: Cannels 120, 124 & 128 on 5GHz

    Posted Feb 13, 2023 04:06 AM

    The way it is supposed to work is that when access points on DFS channels first start up, if they are assigned a DFS channel, they will scan that channel for 10 minutes for radar before broadcasting an SSID.   After that, the access point should always be looking for radar on the current channel.  If the access point detects radar, it will attempt to switch to another channel. If the next channel is a DFS channel, they will scan the target channel for a minute for radar before turning on the radio.

    If your network is designed with enough overlapping coverage, the clients that were attached to that access point will  switch to another access point and not wait on the current access point to change channels.  You don't want this to happen to groups of clients too frequently, so if you get too many radar hits on a specific channel, it is best to just eliminate it from the regulatory domain to avoid this.



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    Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.

    HPE Design and Deploy Guides: https://community.arubanetworks.com/support/migrated-knowledge-base?attachments=&communitykey=dcc83c62-1a3a-4dd8-94dc-92968ea6fff1&pageindex=0&pagesize=12&search=&sort=most_recent&viewtype=card
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    Original Message


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