: Log into your router gateway to note your current build. Step 2: Access Router Gateway
If your HG520B was provided by a telecom company (such as Vodafone, Telekom, or Telmex), check their official support forums or contact customer service. They provide custom, pre-configured, verified firmware packages tailored to their networks.
With the router powered on, insert a paperclip into the small hole on the back panel. Hold it down for 10 to 15 seconds until all lights flash.
Warning: Flashing firmware meant for a different hardware revision will brick the device. Primary Download Channels
This is the safest method. Your router can often "call home" to Huawei servers to pull the latest verified version automatically.
Write down your PPPoE/PPPoA username, password, VPI/VCI values, and Wi-Fi configurations. The upgrade may reset your router to factory defaults. How to Find a Verified Firmware Download