C9800: AP disabling and enabling takes long until 5 GHz is ready

[Johannes Luther]

Hi board,

If I disable and enable an AP using:

ap name myAP shutdown
ap name myAP no shutdown

It takes ages until the 5 GHz radio is ready (example 2802)

What I see in the 5 GHz radio summary is after the AP is enabled, that there is a small "#" sign after the channel:

dest515x-lbwlc103#show ap dot11 5ghz summary
AP Name                           Mac Address     Slot    Admin State    Oper State    Width    Txpwr           Channel                             Mode
---------------------------------------------------------------------------------------------------------------------------------------------------------
myAP                              7079.b3ac.a420  1       Enabled        Up            20       *6/8 (8 dBm)    (120)*#                             Local

=> See that "#" after the channel 120?

What does the "#" exactely indicate? Is it DFS scanning?

If it would be DFS, I would expect, that after I enable the AP, it takes ~60 seconds until the radio is ready. However, it takes approx. 10 minutes

Side facts: Reg Domain -E / AP Model 2802i

[Johannes Luther]

Ok - did some additional testing. This only happens for APs, which are configured for an UNII2 extended channel.

=> So it must be DFS. However I'm missing some documentation on the "#".

It seems, that the 2802 is misbehaving here. For example on a 1562 or 9100 AP, the "#" disappears very fast (~60 seconds).

[JPavonM]

When using TDWR channel from 1120 to 128 in some countries the AP should scan for 10 minutes to avoid interference.

Why 1562 and c9100 APs don't do this is becuase at this time c9100 is not supporting TDWR channels, but for 1562 I don't have that info.

Here you can find some information from Nigel .

HTH

-Jesus

[Johannes Luther]

Hi Jesus,
yeah - it's definately something like this. I have a TAC case regading this and did some additional testing.

First of all (IOS-XE 17.3.3), only the 2802 APs in my lab are able to use the channels 120, 124. 128 (-E domain).

All other APs (9120, 9130, 1562, 2702) are not able to use these channels.

I tested this by assigning a static channel. All models except 2802 throw an error when trying to assign channel 120 - 128.

The TAC told me, that this is an enhancement (CSCvk15657) and obviously this enhancement is only implemented for 2800/3800/4800/1562.  Problem is, that this enhancement is not reflected in the maximum power level Excel sheets and I have not found any other documentation regarding this. From my point of view it's also a little bit inconsistent to implement this differently on different indoor AP models. Normally I would expect, that all indoor APs works the same regarding the usable channels.....