Should AP advertise as HT20/40 if it can only run HT20?

Johannes Berg johannes at
Fri Nov 6 11:24:14 PST 2015

On Fri, 2015-11-06 at 10:51 -0800, Ben Greear wrote:
> We configured an AP to run on channel 6, HT40+.
> But, due to scan results, it decided it could only run HT20 due to
> overlapping BSS.
> The scan results show it as having HT20/40 capability but
> no secondary channel.
> Is this expected?  I was thinking it might should not be advertising
> the HT40.  We are running local patches, possibly we messed up
> something.
No, this is correct and expected. The capability and the actual
operation need not match. In theory, the AP could re-determine later
whether or not it's allowed to operate as HT20 (say the overlapping BSS
goes away) and dynamically reconfigure the *operation* on the fly - it
cannot change its capabilities.


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