FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
This article describes how to fix an issue where FortiWiFi does not immediaetly broadcast the SSID while using the 5GHz Band.
Scope
FortiWiFi.
Solution
According to ITU Resolution 229, there is a need to protect services using 5150-5350 MHz and 5470-5725 MHz bands using mitigation techniques like DFS (Dynamic Frequency Selection).
DFS implements 2 methods for detection:
Channel Availability Check (CAC) - Done before broadcasting on any channel.
In-Service Monitoring (ISM) - Done while broadcasting on a channel. Upon detection, it triggers a frequency change.
Timers:
Default CAC Timer - 1 minute for each channel.
CAC Timer (5600-5650 Mhz) - 10 minutes for each channel.
Translating this information for 5GHz 20MHz wide channels means the following:
CH36-CH48 - These are non-DFS channels so FortiWifi will start broadcasting 'immediately'.
CH52-64, CH100-116, and CH132-144 - FortiWifi will start broadcasting after 1 minute if the first channel is free.
CH120-128 - FortiWifi will start broadcasting after 10 minutes if the first channel is free.
