Technical Tip: How frequency handoff works and when to configure it

laltuzar · ‎07-16-2024

Description

This article describes how frequency handoff is configured and when it is recommended to be enabled.

Scope

FortiAP.

Solution

Frequency handoff is an advanced feature that can be configured based on the FortiAP profile.

This feature encourages clients to connect to 5GHz and 2.4GHz when they support both bands. This is because 5GHz offers more advantages than 2.4GHz.

How this feature works is described as follows and is detailed on Wireless client load balancing for high-density deployments

On a poorly designed or non tuned wireless network, this can cause undesired disconnections. As explained in the documentation above, this is because the clients will be balanced based not only on their dual band support, but mainly on their RSSI too. For example, if there are more than two signals of nearby APs with very good RSSI, more clients will be balanced on the APs nearby (lack of fine tuning - excess of coverage). These disconnections will occur even with very low clients. These disconnections will appear as a complete disconnection, not as seamless roams.

The disconnections can be observed as follows on the WiFi Event logs:

date=2024-05-23 time=12:01:46 id=7372210272947143044 itime="2024-05-23 12:01:03" euid=3 epid=3 dsteuid=3 dstepid=3 logver=700150632 logid=0104043657 type="event" subtype="wireless" level="notice" action="client-association-failure" msg="Client aa:bb:cc:dd:17:53 association failed" logdesc="Wireless station association failed" sn="FP431FTF99999999" user="N/A" reason="Association denied because AP unable to handle additional associated stations" ssid="SSID-NAME" ap="AP-NAME" vap="wifi-oecwsec3" security="WPA/WPA2 Enterprise" channel=6 radioid=1 stamac="aa:bb:cc:dd:17:53" encryption="AES" eventtime=1716476507122131690 remotewtptime="0.0" tz="-0300" devid="FG200FX999999999" vd="root" dtime="2024-05-23 12:01:46" itime_t=1716476463 devname="FORTIGATE-NAME"

date=2024-05-23 time=12:01:46 id=7372210272947143043 itime="2024-05-23 12:01:03" euid=3 epid=3 dsteuid=3 dstepid=3 logver=700150632 logid=0104043595 type="event" subtype="wireless" level="notice" action="client-balanced" msg="Client aa:bb:cc:dd:17:53 balanced for AP-NAME (2), band 5G, sta cnt 5." logdesc="Wireless client load balancing denied" sn="FP431FTF99999999" reason="Client balanced for available 5G band" ssid="SSID-NAME" ap="AP-NAME" vap="wifi-SSID-NAME" stacount=15 radioband="2G" stamac="aa:bb:cc:dd:17:53" eventtime=1716476507122096324 tz="-0300" devid="FG200FX999999999" vd="root" dtime="2024-05-23 12:01:46" itime_t=1716476463 devname="FORTIGATE_NAME"

date=2024-05-23 time=12:01:45 id=7372210264357209788 itime="2024-05-23 12:01:01" euid=3 epid=3 dsteuid=3 dstepid=3 logver=700150632 logid=0104043595 type="event" subtype="wireless" level="notice" action="client-balanced" msg="Client aa:bb:cc:dd:17:53 balanced for AP-NAME (2), band 5G, sta cnt 5." logdesc="Wireless client load balancing denied" sn="FP431FTF99999999" reason="Client balanced for available 5G band" ssid="SSID-NAME" ap="AP-NAME" vap="wifi-SSID-NAME" stacount=15 radioband="2G" stamac="aa:bb:cc:dd:17:53" eventtime=1716476505384471509 tz="-0300" devid="FG200FX999999999" vd="root" dtime="2024-05-23 12:01:45" itime_t=1716476461 devname="FORTIGATE_NAME"

date=2024-05-23 time=12:01:43 id=7372210260062242343 itime="2024-05-23 12:01:00" euid=3 epid=3 dsteuid=3 dstepid=3 logver=700150632 logid=0104043595 type="event" subtype="wireless" level="notice" action="client-balanced" msg="Client aa:bb:cc:dd:17:53 balanced for AP-NAME (2), band 5G, sta cnt 5." logdesc="Wireless client load balancing denied" sn="FP431FTF99999999" reason="Client balanced for available 5G band" ssid="SSID-NAME" ap="AP-NAME" vap="wifi-SSID-NAME" stacount=15 radioband="2G" stamac="aa:bb:cc:dd:17:53" eventtime=1716476504286966970 tz="-0300" devid="FG200FX999999999" vd="root" dtime="2024-05-23 12:01:43" itime_t=1716476460 devname="FORTIGATE_NAME"

date=2024-05-23 time=12:01:41 id=7372210251472308009 itime="2024-05-23 12:00:58" euid=3 epid=3 dsteuid=3 dstepid=3 logver=700150632 logid=0104043595 type="event" subtype="wireless" level="notice" action="client-balanced" msg="Client aa:bb:cc:dd:17:53 balanced for AP-NAME (2), band 5G, sta cnt 5." logdesc="Wireless client load balancing denied" sn="FP431FTF99999999" reason="Client balanced for available 5G band" ssid="SSID-NAME" ap="AP-NAME" vap="wifi-SSID-NAME" stacount=15 radioband="2G" stamac="aa:bb:cc:dd:17:53" eventtime=1716476502502332026 tz="-0300" devid="FG200FX999999999" vd="root" dtime="2024-05-23 12:01:41" itime_t=1716476458 devname="FORTIGATE_NAME"