Features for high-density deployments
High-density environments such as auditoriums, classrooms, and meeting rooms present a challenge to WiFi providers. When a large number of mobile devices try to connect to a WiFi network, difficulties arise because of the limited number of radio channels and interference between devices.
FortiOS and FortiAP devices provide several tools to mitigate the difficulties of high-density environments.
Configuring multiple FortiAP and FortiSwitch firmware upgrades
Administrators can configure multiple FortiAP and FortiSwitch firmware upgrades to occur in one click (under WiFi & Switch Controller > Managed FortiAPs), removing the need to upgrade each device one at a time.
Controlling the power save feature
Occasionally, voice calls can become disrupted. One way to alleviate this issue is by controlling the power save feature, or to disable it altogether.
Manually configure packet transmit optimization settings by entering the following command:
config wireless-controller wtp-profile
edit <name>
config <radio-1> | <radio-2>
set transmit-optimize {disable | power-save | aggr-limit | retry-limit | sendbar}
- disable: Disable transmit optimization.
- power-save: Mark a client as power save mode if excessive transmit retries happen.
- aggr-limit: Set aggregation limit to a lower value when data rate is low.
- retry-limit: Set software retry limit to a lower value when data rate is low.
- send-bar: Do not send BAR frame too often.
11n radio powersave optimization
The following powersave-optimize
parameters (under config radio
) are used for 11n radios to optimize system performance for specific situations.
- tim: Set traffic indication map (TIM) bit for client in power save mode. TIM bit mask indicates to any sleeping listening stations if the AP has any buffered frames present. If enabled, the AP will always indicate to the connected client that there is a packet waiting in the AP, so it will help to prevent the client from entering a sleep state.
- ac-vo: Use Access Category (AC) Voice (VO) priority to send packets in the power save queue. AC VO is one of the highest classes/priority levels used to ensure quality of service (QoS). If enabled, when a client returns from a sleep state, the AP will send its buffered packet using a higher priority queue, instead of the normal priority queue.
- no-obss-scan: Do not put Overlapping Basic Service Set (OBSS), or high-noise (i.e. non-802.11), scan IE into a Beacon or Probe Response frame.
- no-11b-rate: Do not send frame using 11b data rate.
- client-rate-follow: Adapt transmitting PHY rate with receiving PHY rate from client. If enabled, the AP will integrate the current client's transmission PHY rate into its rate adaptation algorithm for transmitting.
Configuring the broadcast packet suppression
You can use broadcast packet suppression to reduce the traffic on your WiFi networks. In addition, some broadcast packets are unnecessary or even potentially detrimental to the network and should be suppressed. To configure broadcast suppression for each virtual access point, enter the following commands:
config wireless-controller vap
edit <name>
set broadcast-suppression {dhcp-up | dhcp-down | dhcp-starvation | arp-known | arp-unknown | arp-reply | arp-poison | arp-proxy | netbios-ns | netbios-ds | ipv6 | all-other-mc | all-other-bc}
end
Option |
Description |
---|---|
|
Suppress DHCP discovery and request packets broadcast by WiFi clients. Forward DHCP packets to the Ethernet uplink only. Prevent malicious WiFi clients from acting as DHCP servers. Default setting. |
|
Suppress DHCP packets broadcast by the Ethernet downlink to WiFi clients. Prevent malicious WiFi clients from acting as DHCP servers. |
|
Suppress DHCP starvation attacks from malicious WiFi clients. Prevent malicious WiFi clients from depleting the DHCP address pool. |
|
Suppress ARP request packets broadcast to known WiFi clients. Instead, forward ARP packets as unicast packets to the known clients. Default setting. |
|
Suppress ARP request packets broadcast to unknown WiFi clients. |
|
Suppress ARP reply packets broadcast by WiFi clients. Instead, forward the ARP packets as unicast packets to the clients with target MAC addresses. |
|
Suppress ARP poison attacks from malicious WiFi clients. Prevent malicious WiFi clients from spoofing ARP packets. |
|
Suppress ARP request packets broadcast by the Ethernet downlink to known WiFi clients. Instead, send ARP reply packets to the Ethernet uplink, as a proxy for WiFi clients.
|
|
Suppress NetBIOS name services packets with UDP port 137. |
|
Suppress NetBIOS datagram services packets with UDP port 138. |
|
Suppress IPv6 broadcast packets. |
|
Suppress multicast packets not covered by any of the specific options. |
|
Suppress broadcast packets not covered by any of the specific options. |
The default configuration enables both the dhcp-up
and arp-known
options. The following example leaves the default settings in place and also configures a virtual access point to suppress:
- unnecessary DHCP down link broadcast packets
- broadcast ARP requests for unknown WiFi clients
- other broadcast packets not specifically identified
config wireless-controller vap
edit <name>
set broadcast-suppression dhcp-up arp-known dhcp-down arp-unknown all-other-bc
end
Converting multicast streams to unicast
FortiOS provides a multicast enhancement option (disabled by default) that converts multicast streams to unicast and improves performance in WiFi networks. Multicast data, such as streaming audio or video, is sent at a low data rate in WiFi networks. A unicast stream is sent to each client at high data rate that makes more efficient use of air time. To enable multicast-to-unicast conversion, enter the following commands:
config wireless-controller vap
edit <vap_name>
set multicast-enhance enable
end
Ignoring weak or distant clients
Clients beyond the intended coverage area can have some impact on your high-density network. Your APs will respond to these clients' probe signals, consuming valuable air time. You can configure your WiFi network to ignore weak signals that most likely come from beyond the intended coverage area. The settings are available in the CLI:
config wireless-controller vap
edit <vap_name>
set probe-resp-suppression enable
set probe-resp-threshold <level_int>
end
vap_name is the SSID name.
probe-resp-threshold is the signal strength in dBm below which the client is ignored. The range is -95 to -20dBm. The default level is -80dBm.
Turning off the 802.11b protocol
By disabling support for the obsolete 802.11b protocol, you can reduce the air time that data frames occupy. These signals will now be sent at a minimum of 6Mbps, instead of 1Mbps. You can set this for each radio in the FortiAP profile, using the CLI:
config wireless-controller wtp-profile
edit <name_string>
config radio-1
set powersave-optimize no-11b-rate
end
Disabling low data rates
Each of the 802.11 protocols supports several data rates. By disabling the lowest rates, air time is conserved, allowing the channel to serve more users. You can set the available rates for each 802.11 protocol: a, b, g, n, ac. Data rates set as Basic are mandatory for clients to support. Other specified rates are supported.
The 802.11 a, b, and g protocols are specified by data rate. 802.11a can support 6,9,12, 18, 24, 36, 48, and 54 Mb/s. 802.11b/g can support 1, 2, 5.5, 6, 9,12, 18, 24, 36, 48, 54 Mb/s. Basic rates are specified with the suffix "basic", "12-basic" for example. The capabilities of expected client devices need to be considered when deciding the lowest Basic rate.
The 802.11n and ac protocols are specified by the Modulation and Coding Scheme (MCS) Index and the number of spatial streams.
- 802.11n with 1 or 2 spatial streams can support mcs0/1, mcs1/1, mcs2/1, mcs3/1, mcs4/1, mcs5/1, mcs6/1, mcs7/1,mcs8/2,mcs9/2, mcs10/2, mcs11/2, mcs12/2, mcs13/2, mcs14/2, mcs15/2.
- 802.11n with 3 or 4 spatial streams can support mcs16/3, mcs17/3, mcs18/3, mcs19/3, mcs20/3, mcs21/3, mcs22/3, mcs23/3, mcs24/4, mcs25/4, mcs26/4, mcs27/4, mcs28/4, mcs29/4, mcs30/4, mcs31/4.
- 802.11ac with 1 or 2 spatial streams can support mcs0/1, mcs1/1, mcs2/1, mcs3/1, mcs4/1, mcs5/1, mcs6/1, mcs7/1, mcs8/1, mcs9/1, mcs0/2, mcs1/2, mcs2/2, mcs3/2, mcs4/2, mcs5/2, mcs6/2, mcs7/2, mcs8/2, mcs9/2.
- 802.11ac with 3 or 4 spatial streams can support mcs0/3, mcs1/3, mcs2/3, mcs3/3, mcs4/3, mcs5/3, mcs6/3, mcs7/3, mcs8/3, mcs9/3, mcs0/4, mcs1/4, mcs2/4, mcs3/4, mcs4/4, mcs5/4, mcs6/4, mcs7/4, mcs8/4, mcs9/4
Here are some examples of setting basic and supported rates.
config wireless-controller vap
edit <vap_name>
set rates-11a 12-basic 18 24 36 48 54
set rates-11bg 12-basic 18 24 36 48 54
set rates-11n-ss34 mcs16/3 mcs18/3 mcs20/3 mcs21/3 mcs22/3 mcs23/3 mcs24/4 mcs25/4
set rates-11ac-ss34 mcs0/3 mcs1/3 mcs2/3 mcs9/4 mcs9/3
end
Enabling the automatic power control
High-density deployments usually cover a small area that has many clients. Maximum AP signal power is usually not required. Reducing the power reduces interference between APs. Fortinet recommends that you use FortiAP automatic power control. You can set this in the FortiAP profile.
- Go to WiFi & Switch Controller > FortiAP Profiles and edit the profile for your AP model.
- For each radio, enable Auto TX Power Control and set the TX Power Low and TX Power High levels. The default range of 10 to 17dBm is recommended.
Enabling frequency band load-balancing
In a high-density environment is important to make the best use of the two WiFi bands, 2.4 GHz and 5 GHz. The 5 GHz band has more non-overlapping channels and receives less interference from non-WiFi devices, but not all devices support it. Clients that are capable of 5 GHz operation should be encouraged to use 5 GHz rather than the 2.4 GHz band.
To load-balance the WiFi bands, you enable Frequency Handoff in the FortiAP profile. In the FortiGate GUI, go to WiFi & Switch Controller > FortiAP Profiles and edit the relevant profile. Or, you can use the CLI:
config wireless-controller wtp-profile
edit FAP221C-default
config radio-1
set frequency-handoff enable
end
The FortiGate WiFi controller continuously performs a scan of all clients in the area and records their signal strength (RSSI) on each band. When Frequency Handoff is enabled, the AP does not reply to clients on the 2.4 GHz band that have sufficient signal strength on the 5 GHz band. These clients can associate only on the 5 GHz band. Devices that support only 2.4 GHz receive replies and associate with the AP on the 2.4 GHz band.
Setting the handoff RSSI threshold
The FortiAP applies load balancing to a client only if the client has a sufficient signal level on 5GHz. The minimum signal strength threshold is set in the FortiAP profile, but is accessible only through the CLI:
config wireless-controller wtp-profile
edit FAP221C-default
set handoff-rssi 25
end
handoff-rssi
has a range of 20 to 30. RSSI is a relative measure. The higher the number, the stronger the signal.
Enabling the AP load balancing
The performance of an AP is degraded if it attempts to serve too many clients. In high-density environments, multiple access points are deployed with some overlap in their coverage areas. The WiFi controller can manage the association of new clients with APs to prevent overloading.
To load-balance between APs, enable AP Handoff in the FortiAP profile. In the FortiGate GUI, go to WiFi & Switch Controller > FortiAP Profiles and edit the relevant profile. Or, you can use the CLI:
config wireless-controller wtp-profile
edit FAP221C-default
config radio-1
set ap-handoff enable
end
When an AP exceeds the threshold (the default is 30 clients), the overloaded AP does not reply to a new client that has a sufficient signal at another AP.
Setting the AP load balance threshold
The thresholds for AP handoff are set in the FortiAP profile, but is accessible only through the CLI:
config wireless-controller wtp-profile
edit FAP221C-default
set handoff-sta-thresh 30
set handoff-rssi 25
end
handoff-sta-thresh
sets the number of clients at which AP load balancing begins. It has a range of 5 to 35.
handoff-rssi
sets the minimum signal strength that a new client must have at an alternate AP for the overloaded AP to ignore the client. It has a range of 20 to 30. RSSI is a relative measure. The higher the number, the stronger the signal.
Setting application rate-limiting
To prevent particular application types from consuming too much bandwidth, you can use the FortiOS Application Control feature.
- Go to Security Profiles > Application Control. You can use the default profile or create a new one.
- Click the category, select Traffic Shaping and then select the priority for the category.
Repeat for each category to be controlled. - Select Apply.
- Go to Policy & Objects > IPv4 Policy and edit your WiFi security policy.
- In Security Profiles, set Application Control ON and select the security profile that you edited.
- Select OK.
Managing the FortiAP group and setting the dynamic VLAN assignment
The FortiGate can create FortiAP Groups, under WiFi & Switch Controller > Managed FortiAPs by selecting Create New > Managed AP Group, where multiple APs can be managed. AP grouping allows specific profile settings to be applied to many APs all at once that belong to a certain AP group, simplifying the administrative workload.
Note that each AP can only belong to one group.
In addition, VLANs can be assigned dynamically based on the group which an AP belongs. When defining an SSID, under WiFi & Switch Controller > SSID, a setting called VLAN Pooling can be enabled where you can either assign the VLAN ID of the AP group the device is connected to, to each device as it is detected, or to always assign the same VLAN ID to a specific device. Dynamic VLAN assignment allows the same SSID to be deployed to many APs, avoiding the need to produce multiple SSIDs.
Sharing tunnel SSIDs within a single managed AP between VDOMs as a virtual AP for multi-tenancy
This feature provides the ability to move a tunnel mode virtual AP (VAP) into a VDOM, similar to an interface/VLAN in VDOMs. FortiAP is registered into the root VDOM.
Within a customer VDOM, customer VAPs can be created or added. In the root VDOM, the customer VAP can be added to the registered FortiAP. Any necessary firewall rules and interfaces can be configured between the two VDOMs.
Syntax
config wireless-controller global
set wtp-share {enable | disable}
end
Enabling the manual quarantine of devices on FortiAP (tunnel mode)
Quarantined MAC addresses are blocked on the connected FortiAP from the network and the LAN. When a tunnel VAP is created, a sub-interface named wqtn is automatically created under tunnel interface. This sub-interface is added under a software switch.
To quarantine an SSID, go to WiFi & Switch Controller > SSID. Edit the SSID, and enable Quarantine Host is enabled under WiFi Settings.
Alternatively, this can be configured in the CLI Console. This feature consolidates previous CLI syntax for quarantining a host, so that the host does not need to be configured in multiple places (FortiAP and FortiSwitch). Host endpoints can be entered in a single place and the host will be quarantined throughout the access layer devices on the Fortinet Security Fabric.
|
Note that you can only an SSID in Tunnel Mode. |
Syntax - SSID:
config wireless-controller vap
edit <name>
set quarantine {enable | disable}
next
end
Syntax - Software Switch, DHCP, and User Quarantine
config system switch-interface
edit "wqt.root"
set vdom "root"
set member "wqtn.26.AV-Qtn"
next
end
config system dhcp server
edit <id>
set interface "AV-Qtn"
config ip-range
edit <id>
set start-ip 10.111.0.2
set end-ip 10.111.0.254
next
...
config user quarantine
set quarantine {enable | disable}
end
To list stations in quarantine, use the following diagnose command:
diagnose wireless-controller wlac -c sta-qtn
Host quarantine per SSID
Upon creating or editing an SSID, a Quarantine Host option is available to enable (by default) or disable quarantining devices that are connected in Tunnel-mode. The option to quarantine a device is available on Topology and FortiView WiFi pages.
When a host is put into quarantine VLAN, it will get its IP from the quarantine VLAN's DHCP server, and become part of the quarantined network.
Syntax
config wireless-controller vap
edit <name>
set quarantine {enable | disable}
next
end
To list all stations in quarantine:
diagnose wireless-controller wlac -c sta-qtn
Locating a FortiAP with LED blinking
If you have an environment that contains numerous APs, and there is one AP that you need to frequently monitor, you can configure it to blink in the FortiCloud web portal. The blinking AP will be easier to locate.
To start or stop LED blinking of a managed FortiAP, using the GUI:
- Go to WiFi & Switch Controller > Managed FortiAPs.
- Right-click in the row of the device you want to control.
- In the dialog box, scroll down to LED Blink and select Start or Stop.
The following models support LED blink control through the GUI, operating on FortiAP software 6.0.1, or later:
- FortiAP-112D, 221C, 223C, 224D, 320C, 321C
- FortiAP-S/W2
To start or stop LED blinking of a managed FortiAP, using the CLI:
execute wireless-controller led-blink <wtp-id> {on | on 10 | off}
The following models support LED blink control through the CLI, operating on FortiAP software 5.6.2, or later:
- FortiAP-112D, 221C, 223C, 224D, 320C, 321C
- FortiAP-S/W2
Uploading a FortiAP image on the wireless controller
Using the CLI to upgrade FortiAP image is the preferred method especially for large deployments. Use the following execute command to upload the desired FortiAP image on the controller:
execute wireless-controller upload-wtp-image
After entering the command, reboot the FortiAP devices. This feature allows the administrator to configure all FortiAP devices to download the image from the controller at join time.
Syntax
config wireless-controller global
set image-download {enable | disable}
end
To fine-tune this process, in order to deploy FortiAP image upgrades to a subset of devices for pilot testing, use the following command:
config wireless-controller wtp
edit <name>
set image-download {enable | disable}
next
end
Configuring control message off-loading
Users can configure control message off-loading to optimize performance. This is especially useful in environments where the AP count is around 300-350 (with a device count between 1500 and 3000), where existing users are disconnected and unable to reauthenticate due to high CPU usage. This feature includes aeroscout enhancements. See CPU and memory thresholds for information on customizing the CPU use threshold.
Syntax
config wireless-controller global
set control-message-offload {evp-frame | areoscout-tag | ap-list | sta-list | sta-cap-list | stats | aeroscout-mu}
end
config wireless-controller wtp-profile
edit <name>
set control-message-offload {enable | disable}
config lbs
set ekahau-blink-mode {enable | disable}
set aeroscout {enable | disable}
set aeroscout-server-ip <address>
set aeroscount-server-port <UDP listening port>
set aeroscout-mu {enable | disable}
end
end