Technical Tip: FortiAPs with external antennas

[pdw8]

Description	This article describes how to configure and understand the new external antenna feature in FortiAP.
Scope	FortiAP.
Solution	In FortiAP v7.2.3 and from 7.4.0, it is now possible to select an external Fortinet antenna model or choose a Custom figure for third party antennas. The Fortinet antenna selection is currently possible to select for FAP-432F and FAP-433F models.  Custom is available on the APs listed below. FortiAP F models FAP-432F FAP-432FR FAP-433F FortiAP G models FAP-233G FAP-432G FAP-433G FortiAP U-F models FAP-U432F FAP-U433F FortiAP K models (supported from FOS 7.6.4+) FAP-243K FAP-443K Scenario 1 - Using the supplied dipole antennas. In this scenario, the AP has the factory-supplied dipole antennas in use, so an external antenna option is NOT required. However, the gain of the dipoles is now considered by the FortiGate, and this is included in the target TX power setting. The image below shows the result of this. The optional antenna is set to None, and FortiGate knows that the default dipole antenna gain is 6dBi. Target TX power is 15dBm set in the FortiAP profile. Configured / operating TX power is 9dBm. EIRP is TX power 9 + gain 6 = 15dBm target. Scenario 2 – Using an external Fortinet antenna with FortiAP432F & FortiAP433F. In the relevant FortiAP profile (remember this is only for FortiAPs with external antenna connectors), locate the External antenna radio button and enable it. A dropdown menu will appear with all possible Fortinet antennas compatible with the specific FortiAP. Note that only the FortiAP432F and FortiAP433F have the antenna list at this time. Here, choose either the correct antenna model or choose Custom for a third-party antenna. In this example, the 8065-P-N is selected. This has a gain of 8dBi on 2.4Ghz and 6.5dBi on 5Ghz. The FortiGate now has the antenna gain and will INCLUDE this in the configured transmit power range. The FortiAP profile has a fixed TX power at 15dBm on both bands. On the AP CLI, use the command 'rcfg' (below is a snippet of the output). rcfg Radio 0: AP    country        : cfg=GB oper=GB    countryID      : cfg=826 oper=826    radio type     : 11AX_2.4G (pure G)    mimo,chainmask : 4, 0xf (mimo) 0xf (power) 0xf/0xf (oper)    opt antenna    : FANT_04ABGN_8065_P_N    txpwr mode     : set by value (15 dBm)    txpwr cfg/oper : 7/7 (EIRP +8)    VHT param      : gi=disabled bw=20MHz    oper_chan      : 1 txpwr mode: set by value (15 dBm) - This is the fixed TX power chosen in the FortiAP Profile. txpwr cfg/oper: 7/7 (EIRP +8) - This is the configured / operating power, so the FortiAP power is 7dBm + 8dBi gain, and it adds up to 15dBm TX power defined in the profile. Operating power is the EIRP total. The 5GHz radio shows a similar output: rcfg Radio 1: AP    country        : cfg=GB oper=GB    countryID      : cfg=826 oper=826    radio type     : 11AX_5G    opt antenna    : FANT_04ABGN_8065_P_N    txpwr mode     : set by value (15 dBm)    txpwr cfg/oper : 9/9 (EIRP +6)    channel        : num=149    oper_chan      : 149 txpwr mode: set by value (15 dBm). This is the fixed TX power chosen in the FortiAP Profile. txpwr cfg/oper : 9/9 (EIRP +6). This is the configured / operating power, so the FortiAP power is 9dBm + 6dBi gain, and it adds up to 15dBm TX power defined in the profile. Operating power is the EIRP total. Scenario 3 – Using an external antenna in Custom mode. In the relevant AP profile (remember this is only for FortiAPs with external antenna connectors), locate the External antenna radio button and enable it. A menu will appear with the word Custom and a sub-menu with antenna gain value. At this point, refer to the antenna documentation to determine the antenna gain. It is often a different value between bands and needs to be enabled and set on each radio. Enter the manufacturer's gain value and save the profile. The FortiAP profile will now have the manually added custom external antenna gain. In this example, 7dBi. The target TX power is 15dBm. On the FortiAP CLI, use the command 'rcfg' (below is a snippet of the output): rcfg Radio 1: AP    country        : cfg=GB oper=GB    countryID      : cfg=826 oper=826    radio type     : 11AX_5G    opt antenna    : Custom    opt ant gain   : 7    txpwr mode     : set by value (15 dBm)    txpwr cfg/oper : 8/8 (EIRP +7)    VHT param      : gi=disabled bw=40MHz    ack timeout    : 25 txpwr mode: set by value (15 dBm) - This is the fixed TX power chosen in the FortiAP Profile. txpwr cfg/oper: 8/8(EIRP +7) – This is the configured / operating power, so the FortiAP power is 8dBm + 7dBi gain, and it adds up to 15dBm TX power defined in the profile. Operating power is the EIRP total.