ZyWALL USG20W-VPN - Firmware V5.41(ABAR.0)

Options
AirV68
AirV68 Posts: 2 image  Freshman Member
in Security

Hello,

After upgrading to firmware V5.41(ABAR.0), VLAN-connected devices gradually lost connectivity. The main LAN remained functional.

Restoring a backup configuration made before the firmware upgrade immediately restored all VLAN and DHCP functions.

Firmware V5.41(ABAR.0) appears to break DHCP/VLAN bindings or interface-zone associations during upgrade, causing VLAN clients to lose connectivity progressively as DHCP leases expire.

Can you please confirm and help?

Thanks,

AirV68

All Replies

  • PeterUK
    PeterUK Posts: 4,411 image  Guru Member
    250 Answers 2500 Comments Friend Collector Eighth Anniversary
    edited October 2025

    Well I don't use DHCP much in my network but when you upgrade firmware I believe all DHCP clients when you have "Enable IP/MAC Binding and DHCP Enforcement" the USG knows nothing on reboot and so clients must DHCP before being allowed which if clients are connected to a switch they stay on the lease they were given but not allowed by USG until they DHCP.

    You can solve this by rebooting the switch or set a low lease time like 3 minutes.

    On V4.73 there was "Enable IP/MAC Binding" which meant the USG would allow clients that it did not know to connect without needing to DHCP but in V5.?? (not sure when the change happened) its "Enable IP/MAC Binding and DHCP Enforcement" as said above.

  • PeterUK
    PeterUK Posts: 4,411 image  Guru Member
    250 Answers 2500 Comments Friend Collector Eighth Anniversary
    edited October 2025

    Also you want to disable IP Auto configuration on windows

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

    32bit DWORD

    IPAutoconfigurationEnabled = 0

  • Zyxel_Tina
    Zyxel_Tina Posts: 642 image  Zyxel Employee
    Zyxel Certified Network Administrator - Security Zyxel Certified Network Administrator - Switch 100 Answers 500 Comments

    Hi @AirV68,

    To investigate further, could you please provide your configuration file with us?

    Zyxel Tina

  • Radik
    Radik Posts: 2 image  Freshman Member
    First Comment Friend Collector First Anniversary

    Hello,

    I encountered an issue with firmware 5.41 Patch 0 on a USG20W-VPN. Wireless clients stop obtaining IP addresses from the DHCP server. I performed multiple configuration checks and reconfigured the device several times, but the issue persisted.

    After rolling back to firmware version 5.40 Patch 0, the issue was resolved, and wireless clients started receiving IP addresses normally.

    Unfortunately, I was unable to collect diagnostic data and logs, as the client’s office is located far away and they could not wait for extended troubleshooting.

  • Zyxel_Tina
    Zyxel_Tina Posts: 642 image  Zyxel Employee
    Zyxel Certified Network Administrator - Security Zyxel Certified Network Administrator - Switch 100 Answers 500 Comments

    Hi @Radik,

    Since this issue occurs on firmware v5.41 and v5.42 is now available, we'd first recommend upgrading to the latest firmware. After the upgrade, please test again and let us know if the issue persists. If so, could you please provide the config file or screenshots of the settings you applied to help us investigate further? This will allow us to reproduce the problem locally and identify the root cause.

    Zyxel Tina

  • Radik
    Radik Posts: 2 image  Freshman Member
    First Comment Friend Collector First Anniversary
    https://community.zyxel.com/en/discussion/comment/83377#Comment_83377

    Hi Tina. FW v5.42 works good. Thank you and have a great day!

Categories

Security Help Center

EnglishTiếng ViệtРусскийไทย中文（台灣）