Here you can know how to factory reset any Synology router for free. You don’t need any tools to reset with these methods.
You cannot update any security settings unless you know the username and password and access the router’s configuration utility. If you didn’t remember the router’s username and password or your login credentials stop working, you must reset your router.
You must need basic knowledge about computer and browser to reset Synology router with Web-based configuration utility. You can easily reset and reboot with this utility, don’t need to download any software or tool for this method. All routers have this Reset button. Reset delete all internet or and wireless settings on your device (IP addresses, DNS details, WiFi password, etc).
Rebooting the router and resetting the router are two different approaches. The reboot is a simple process and should be tried before you reset. If the rebooting router does not fix the problem, Resetting the router is still available.
Factory resetting the router will erase all changes you made to the router. Internet/Wireless Settings will need to be reconfigured.