NetworkManager can only use Wi-Fi band "a" or "bg" if the 802-11-wireless.band property is set. It is done via specifying allowed frequences to wpa_supplicant.
It does not work as expected though. NetworkManager sets wpa_supplicant's 'freq_list' option as comma-separated frequences, but wpa_supplicant expects space-separated list.
See upstream bug https://bugzilla.gnome.org/show_bug.cgi?id=627571#c11
and branch jk/freq-list-bgo627571 for a fix.
Let's put the following commit to RHEL 7.2
c8b5b5e supplicant: wpa_supplicant wants space-separated list in freq_list (bgo #627571)
It fixes the bug. The rest of the upstream branch will get into RHEL when we rebase to NM 1.0.6.
Verified band locking works by a series of automated test on several different wireless HW devices available.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.