Best Practice – Wireless
The following section contains a list of best practices for wireless network configurations with regard to encryption and authentication, geographic location, network planning, power usage, client load balancing, local bridging, SSIDs, and the use of static IPs.
Encryption and authentication
It is best practice to always enable the strongest user authentication and encryption method that your client supports. Fortinet recommends the following security, in order of strongest to weakest:
l WPA2 – Enterprise 802.1x/EAP – Personal pre-shared key (8-63 characters) l WPA – Enterprise 802.1x/EAP – Personal pre-shared key (8-63 characters) l WEP128 – 26 Hexadecimal digit key l WEP64 – 10 Hexadecimal digit key l None – Open system
Ensure that the FortiGate wireless controller is configured for your geographic location. This ensures that the available radio channels and radio power are in compliance with the regulations in your region.
The maximum allowed transmitter power and permitted radio channels for Wi-Fi networks depend on the region in which the network is located. By default, the WiFi controller is configured for the United States. If you are located in any other region, you need to set your location before you begin configuring wireless networks.
The location setting can only be changed from CLI. To change the country to France, for example, enter the following:
config wireless-controller setting set country FR
To see the list of country codes, enter a question mark (‘?’) in place of the country code.
Using an incorrect geographic location is a common error that can lead to unpredicable results on the client side.
It is recommended that you perform a proper site survey prior positioning the wireless access point. In order to evaluate the coverage area environment, the following criteria must be taken into account:
l Size of coverage area l Bandwidth required l Client wireless capabilities Wireless Lowering the power level to reduce RF interference
After completing a RF site survey, you’ll have a good idea of the number and location of access points needed to provide users with adequate coverage and performance.
However, prior to installing the access points, be sure to determine the RF channel(s) you plan to use. This will ensure that users can roam throughout the facility with substantial performance.
To avoid co-channel interference, adjacent Wi-Fi APs must be configured to use non-overlapping channels. Otherwise, you’ll find poor performance will degrade because of interference between access points.
It is recommended to statically configure the non-overlapping channels on every access point, using one Custom AP profile per AP (or group of APs). If static configuration cannot be used, the FortiOS Wi-Fi Controller includes the Automatic Radio Resource Provisioning (ARRP) feature.
Lowering the power level to reduce RF interference
Relevant Product(s): FortiAP
Reducing power reduces unwanted coverage and potential interference to other WLANs. Areas of unwanted coverage are a potential security risk. If possible, reduce the transmitter power of your wireless access point so that the signal is not available beyond the areas where it is needed. Auto Tx Power Control can be enabled to automatically adjust the transmit power.
In cases where customers complain about slow wireless traffic through a FortiAP, it might be necessary to try to reduce the possibility of RF interference. It is best practice not to locate FortiAPs near steel beams or other interfering materials. You can try using a wireless sniffer tool to collect the wireless packets and then analyze the extent of air interference.
A common mistake is spacing FortiAPs based upon the 5Ghz radio frequency. The 2.4Ghz signal travels further.
You have two options when confronted with slow wireless traffic through a FortiAP:
Option #1: Reducing transmit power
Perform a speed test and record the results. Set one of the radios on a FortiAP to be in dedicated monitoring mode. Then observe how many APs are detected. If the number of APs is too high (i.e., greater than 20), try reducing the transmit power in the WTP profile for the FortiAPs until the number of dedicated APs has dropped significantly.
Repeat the speed test.
Option #2: Ensuring that VAPs are distributed over the available channels
No built-in tools are available to measure RF interference directly. However, FortiOS 5.0 does allow for automatic power adjustment, which should minimize the occurrence of RF interference.
Wireless client load balancing
Wireless load balancing allows your wireless network to more efficiently distribute wireless traffic among wireless access points and available frequency bands. FortiGate wireless controllers support the following types of client load balancing:
- Access Point Hand-off – The wireless controller signals a client to switch to another access point.
- Frequency Hand-off – The wireless controller monitors the usage of 2.4GHz and 5GHz bands, and signals clients to switch to the lesser-used frequency.
Whenever possible, use local bridging to offload the CAPWAP tunnel. Note that in this case, Wi-Fi client devices obtain IP addresses from the same DHCP server as wired devices on the LAN. The vlan ID can only be configured from the CLI:
config wireless-controller vap edit “vaplocalbridge” set vdom “root” set ssid “testvaplocalbridge” set local-bridging enable set vlanid 40 —> only available in CLI
- It is highly recommended to advertise the SSID. It makes it easier for customers and wireless clients. Also, if you ‘hide’ the SSID (known as ‘network cloaking’), then clients will always look for it when they’re outside the coverage area, which searches for known SSIDs, in effect leaking the SSID anyway. Refer to RFC 3370. Furthermore, many of the latest Broadcom drivers do not support hidden SSID for WPA2.
- For security reason, you might want to prevent direct communication between your wireless clients. In this case, enable Block Intra-SSID Traffic (in the SSID configuration).
- In a network with multiple wireless controllers, you need to change the mesh SSID so that each mesh root has a unique SSID. Other controllers using the same mesh root SSID might be detected as fake or rogue APs. Go to WiFi & Switch Controller > SSID to change the SSID. Fortinet also recommends that you create a new preshared key instead of using the default.
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