Troubleshooting Tip: Error 'Invalid FortiSwitch Serial Number' when manually adding specific FortiSwitch devices

[nkorea]

Description	This article discusses a known issue where attempting to pre-configure certain FortiSwitch models for FortiGate management (i.e. manually entering the FortiSwitch serial number under the Managed FortiSwitches section of the GUI) will result in an error message being triggered that states 'Invalid FortiSwitch Serial Number'.
Scope	FortiGate, certain FortiSwitch G-series and FortiSwitch Rugged F-series models.
Solution	As a brief primer, there are two methods to add a FortiSwitch to a FortiGate for FortiLink management: Using FortiSwitch Auto-Discovery and Authorization (where the FortiGate dynamically discovers the FortiSwitch via FortiLink and LLDP, then authorizes it to be joined for management). Manually adding the FortiSwitch's Serial Number to the FortiGate (useful for pre-configuring the FortiSwitch before it is connected to the network). In FortiOS 7.4.8 and earlier, the FortiGate will return an error stating 'Invalid FortiSwitch Serial Number' when the administrator attempts to manually add one of the following FortiSwitch models: FortiSwitch Rugged 216F-POE FortiSwitch Rugged 112F-POE FortiSwitch Rugged 108F FortiSwitch 110G-FPOE FortiSwitch 124G FortiSwitch 124G-FPOE The following screenshot shows an example of this error message, which is found under WiFi & Switch Controller -> Managed FortiSwitches after selecting Create New -> FortiSwitch: Resolution: This issue is tracked by Issue #1155476 and will be resolved in the upcoming FortiOS 7.4.9 (this issue does not impact FortiOS 7.6). Workaround: This issue only affects the aforementioned FortiSwitch/FortiSwitch Rugged models when they are added manually via the pre-configuration method. This issue does not impact these same FortiSwitch models if they are added through the automatic FortiLink discovery process, so the recommended workaround at this time is to avoid manually adding the FortiSwitch serial number to the FortiGate and instead populate it via FortiLink discovery. Related documents: Technical Tip: FortiSwitch Auto-Discovery and Authorization FortiSwitch v7.0.8 Devices managed by FortiOS | Discovering, authorizing, and deauthorizing FortiSwi...