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ExtremeWireless Auto Channel selection

  • 1.  ExtremeWireless Auto Channel selection

    Posted 02-02-2017 07:35
    Hi Community

    So I have a question for the community and would like to get your comments on the topic.
    I have been deploying the solution for years now (From when Enterasys started with the product).

    When I do the initial configuration of the controller, I usually configure the AP's default settings to Auto select the Channel for both 2.4Ghz and 5Ghz.

    With the various code releases "Dynamic Channel Selection" was introduced, some version setting this to Monitor only and other version setting this to Active Mode by default.

    The question I have is that at most of the deployments across the years I have seen that the AP's would all place their channels on both the 2.4Ghz and 5Ghz on the same channel.

    I usually end up with statically assigning Channels to avoid the same channel selection.
    I understand that I might have outside interference cause all the AP's to try and hog the same channel.... But I have seen other systems deployed in the same space and the channel selection was perfect, every AP on it own unique channel.

    What have you experienced on this, lets discuss your experience regarding this matter and your recommendations.


  • 2.  RE: ExtremeWireless Auto Channel selection

    Posted 02-02-2017 07:43
    Hello, Andre!

    I think it's depends on phisical topology, numbers of AP's, numbers of clients, functional which work at AP's...

    DCS - it's good functional, but if there is a lot of AP's, clients then AP's have to have some time to relocate to other channels and it's can be critical for applications.
    So in this case, in my mind, you have to configure statical channel plan.

    If you have not so many AP's, not so many clients, a lot of interferences, so it's better to enable DCS.

    Thank you!

  • 3.  RE: ExtremeWireless Auto Channel selection

    Posted 02-02-2017 08:07
    Andre - it would be interesting to understand how long you waited between powering up the AP's and determining that all are on the same channel. If you look shortly after initial power-up you will find many adjacent AP's on the same channel (2.4GHz more likely, given the fewer number of channels).

    The DCS algorithm takes some time - during an initial deployment - to level out and determine all of the correct channels for operation. Depending on the size and density of deployment this may take longer.

  • 4.  RE: ExtremeWireless Auto Channel selection

    Posted 02-02-2017 08:21

    We don't use the active mode. All radio's are in monitor.
    We manually create our channel plan and adjust where necessary with auto channel select.
    Also we monitor the dcs threshold and noise values through snmp.

    This is a good guide for initial setup but like you my experience that dcs active mode is also not so good:


  • 5.  RE: ExtremeWireless Auto Channel selection

    Posted 02-02-2017 13:45
    Personally we've stayed clear of Active DCS. In the older 9.x track, about 2 years ago, we had a lot of issues with AP's rebooting due to DCS being in active mode. Recently on the 10.x release, DCS wasn't reporting correct threshold numbers, which was fixed in 10.11.05.

    I would love for DCS and auto tx to work flawlessly, as micro managing channels consumes more time than I would like. Now that the firmware we are on seems stable, it might be time for me to re-visit DCS functionality.

    I've also run into the same thing where Auto channel selection chooses the same channel across AP's, but i never knew that manually running ACS was recommended after boot. That's really good to know and i'll have to play with it at some point.

    I'm also interested to hear from anyone who is successfully using Active DCS and what thresholds they are using, specifically in a dense urban environment.

  • 6.  RE: ExtremeWireless Auto Channel selection

    Posted 02-06-2017 14:05
    Our experience is the same, new APs mainly select the same channels. Even if they are in the same room, they very often have the same channel. This channel selection will be retained as long as DCS is in Monitor mode or in active mode with high tresholds.

  • 7.  RE: ExtremeWireless Auto Channel selection

  • 8.  RE: ExtremeWireless Auto Channel selection

    Posted 02-08-2017 11:59
    Hi guys

    I thought I'd add to this. More a question than a comment. I've noticed something on the current channel which I don't recall seeing before. The current channel displays "auto-site" which seems to be inherited from somewhere. When looking at the assigned channel it is the same as surrounding AP's. Anyone seen this before? Any ideas as to why this is displayed?


  • 9.  RE: ExtremeWireless Auto Channel selection

    Posted 02-08-2017 11:59

    This is part of the new channel inspector in 10.21, you can kick off background or auto scan from the channel inspector report.


  • 10.  RE: ExtremeWireless Auto Channel selection

    Posted 02-02-2017 08:22
    From my experience if you turn on all APs at the same time they will end up on the same (first) channel (=DCS in monitor mode).
    So if you see all using 36 you'd need to force ACS again = multiedit all APs to channel auto.
    ACS only runs turing the first time the AP comes up or if you force it with channel=auto.

    There is document somewhere that tells you to force ACS as soon as all APs are on during a new deployment.

  • 11.  RE: ExtremeWireless Auto Channel selection

    Posted 02-02-2017 08:22
    I agree with this. If you power up all the AP's at the same time, then you run into this issue. I have had good luck doing one AP at a time and having them select proper channels. It is a lot more time intensive, but it results in better channel selection with minimal Co-Channel Interference.

  • 12.  RE: ExtremeWireless Auto Channel selection

    Posted 02-02-2017 08:22
    Hi Ron,

    i this a argument to use or to disuse ACS? Are the channels spreaded in a good way all over?

    Here are a GTAC Article that helps understanding ACS: