This article provides information about the maximum number of AX411 licenses that can be installed on SRX branch series on 10.4 and 11.2 onwards.
The following error is generated, after upgrading the device to Junos version 11.2 (although everything was working fine on Junos version 10.4.):
terminal:1 error: JUNOSXXXXXX: license not valid for this product add license complete (1 errors)
The following link mentions the maximum AX411 Access points supported on respective devices: http://www.juniper.net/techpubs/en_US/release-independent/junos/topics/concept/access-point-ax411-description.html Although on version 10.4 & below, the device used to accept the licenses beyond the supported number. The same was listed in the Junos® OS 10.4 Release Notes :
"SRX220 Services Gateways running Junos OS Release 10.4R1 or later releases support the AX411 Access Point in the same manner as do the SRX210, SRX240, and SRX650 Services Gateways. Support for the SRX220 Services Gateway is not documented in the AX411 Access Point Hardware Guide or in the WLAN Configuration and Administration Guide, but wherever those guides indicate support for the SRX210 Services Gateway, that support applies to the SRX220 Services Gateway as well."
"AX411 Access Points On SRX210, SRX240, and SRX650 devices, up to four access points (maximum) can be configured and managed."
You have to purchase a license according to your device. If you have a license for 2 users as free on your device, then additionally purchase a license for 2 AX411. The available licenses are: