I haven't been able to find a way to disable 802.11a clients from connecting to the 5 GHz radio on an 802.11n AP. Regardless of Greenfield not yet supported, it would be desirable to ensure 802.11a clients can not connect to the 5 GHz radio. As the majority of 802.11a clients are 802.11a/b/g clients, these clients would instead connect to the 2.4 GHz radio. 802.11a-only clients obviously could not connect at all, but very few of these exist in the enterprise these days.
All discussion regarding band steering from Cisco and other vendors indicates that not only will 802.11n clients be steered to the 5 GHz band but 802.11a clients will also. Hence, a way to disable 802.11a support on the autonomous and lightweight APs would be nice. At least one 802.11a rate must be selected and I can see no other way of disabling support. Suggestions?
The alternative I am looking at currently is a script to detect whether the client is 802.11n capable and push them to the 5 GHz SSID. Else, they will get the 2.4 GHz SSID. If this script is based on chipsets instead of some O/S info that indicates chipset support, it will obviously mean that is requires maintenance to stay current with new chipsets, which is a pain.