Welcome to the Firewall FAQ section of Zyxel's Technical Portal. The Zyxel USG FLEX H Series Firewalls are critical for protecting your network from unauthorized access and cyber threats. Whether you are configuring security policies, troubleshooting connectivity issues, or optimizing performance, this guide addresses the most common questions about the USG FLEX H Series. We aim to help you maintain a secure, efficient, and high performance network environment with the advanced capabilities of Zyxel's next-generation firewalls.
Frequently Asked Questions
Critical Updates
Please stay updated with key security updates.
Weekly Firmware / Support Version / Lab Version
Introduction and basic setup
USG FLEX H Series [Firewall] - Initial Setup Wizard
Easy Support Assistance
- USG FLEX H Series [Firewall] - How to creating a Diagnostic File
- USG FLEX H Series [Firewall] - How to allow HTTPS Web GUI Access from WAN?
- USG FLEX H Series [Firewall] - Right Console Cable and LED Indication
- USG FLEX H Series [Firewall] - Packet Capture
- Zyxel USG FLEX H [Firewall] - Bootup Status Introduction on USG FLEX H Series Firewall
- USG FLEX H Series [Firewall] - reset or reboot the device and LED light indicates your H Series Firewall
- USG FLEX H Series [Firewall] - upgrade/update procedure
- USG FLEX H Series [Firewall] - Overview of CLI Commands for H Series
- USG FLEX H Series [Firewall] - how to backup/restore a configuration file
- USG FLEX H Series [Firewall] - Configure IPSec Site-To-Site VPN on USG FLEX H Series Firewall with static IP
- Zyxel USG FLEX H Series Firewall - Internet access problem when first starting/initializing the device
Overview & Initial Setup
- USG FLEX H Series uOS - Initial Setup USG FLEX H Series Firewall
- Zyxel USG FLEX H Series Feature Matrix - uOS Feature Comparison with ZLD
- Zyxel USG FLEX H Series Firewall - Internet access problem when first starting/initializing the device
- Zyxel USG FLEX H Series Firewall - Protection Key Features Overview
- Zyxel USG FLEX H Firewall - Bootup Status Introduction on USG FLEX H Series Firewall
Licensing
- Zyxel USG FLEX H Series – Enhanced License Transfer and Migration in Nebula Control Center
- How the Secure WiFi License Works on Zyxel USG FLEX H-Series Firewalls
Maintenance
- Handbook for Security Products: Complete Guide for Zyxel FLEX H Series Devices
- USG FLEX H Series – WAN Interface Configuration with Static IP and DNS Settings
- Zyxel USG FLEX H Series — Configure Search Base DN and Bind DN Base for Active Directory Authentication
- USG FLEX H external captive portal with SignLogger RADIUS authentication
- Zyxel USG FLEX H Firewall - Which MFA Methods Are Supported in uOS for Outbound Authentication
Security Services
- Zyxel Firewall USG FLEX H - How to Configure IP Exception to Bypass Security Services via Local Web GUI
- 2FA with REINER SCT Authenticator
- Zyxel USG FLEX H Series Firewall - How to Block HTTPS Websites Using Content Filtering and SSL Inspection
- USG FLEX H Series Firewall - How to use the Geo-IP feature?
Network
- Zyxel USG FLEX H Series Firewal - How to Configure DHCP Option 60 Vendor Class Identifier
- Bridge Interface Enhancements in Zyxel USG FLEX H Series [uOS] Firewalls
- Zyxel USG FLEX H Series - WAN Trunk Load balancing for USG FLEX H series
- Zyxel Virtual Server Port Forwarding NAT - how to configure Virtual Server Port Forwarding on the Zyxel USG Flex H Series firewall
- Zyxel Firewall NAT - how to configure NAT 1 to 1 Network Address Translation on the Zyxel USG Flex H Series firewall
VPN
- Nebula Site-to-Site VPN — Configure Site-to-Site VPN Between Nebula Gateways Using Standard VPN and VPN Orchestrator
- Site-to-Site VPN with NAT on Zyxel USG FLEX H - Configuration Guide
- Using Nebula-Assigned Domain Names for Remote Access VPN
- How to Configure SSL VPN Connection on Zyxel USG FLEX H Series (with OpenVPN Connect)
- Site-to-Site IPSec VPN - CHILD_SA config '<name>' not found on
HA - High Availability (HA PRO)
- Always-On Network Security with USG FLEX H Series and HA - Questions and Answers
- How can I access or ping the passive HA Pro device from a LAN client?
- Zyxel H Series — License Behavior in Device HA Mode
- Zyxel USG FLEX H Series HA - Firmware Update in High Availability HA Mode
- Zyxel USG FLEX H Series HA - Replace the device or re-deploy HA HA PRO
FAQ Express
- How to Check Nebula Information on Zyxel USG FLEX H Series via CLI
- What happens if you set automatic firmware updates for Zyxel H-Series in both Nebula and the local interface?
- FAQ-E Zyxel USG FLEX H Firewall uOs - SSL VPN Error - The number of subnets you set has reached the limit.
- FAQ-E - Is HA Support on USG FLEX H uOS in Nebula?
- FAQE USG FLEX H Series uOS 1.32 - Changes and special behavior of Captive Portal in UOS 1.32
- INT Zyxel Firewall H Series — Operating Modes and Management Scenarios
- How to Configure PPPoE on the WAN Interface of Zyxel USG FLEX H Series
- License Transfer Behavior Between Zyxel USG FLEX / ATP Series and USG FLEX H-Series
- AP Controller Enhancements - MAC Filtering on Zyxel AP Controller (Firmware V1.36)
- Why Cloud Firmware Upgrade Is Disabled When an ITS Weekly Build Is Installed
- How to re-register or delete/remove a USG FLEX H-Series device from the Nebula Cloud platform
- How to register a USG FLEX H-Series device on the Nebula Cloud platform
- How to Enable and Check Debug Level (log level 8) on Zyxel USG FLEX H Series
- How to Reset a Forgotten Administrator Password on Zyxel USG FLEX H Series (Without Resetting Configuration)
- Zyxel Firewall Certificate - How to Recover or Regenerate the Default Device Certificate on a Zyxel Firewall Using the CLI
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