SSL VPN with Radius authentication fails to connect after few days

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nielsscheldeman
nielsscheldeman image  Ally Member
First Comment Friend Collector Fourth Anniversary
in USG FLEX H Series

I have set up SSL VPN on ZyXEL FLEX 200H with Radius Authentication. This all works fine, but after a few days users can't connect anymore. I don't see anything in my NPS logs and also no connection tries in de FLEX. If I do a telnet to the port, it's not responding. If I turn off SSL VPn and turn it back on, everything works fine.

So would this be a bug? Or some sessions that fill up? Frustrating thing is that I don't see it in the logs. I run on V1.38(ABWV.0)

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  • Zyxel_Judy
    Zyxel_Judy image  Zyxel Employee
    Zyxel Certified Network Engineer Level 2 - Nebula Zyxel Certified Network Engineer Level 2 - Switch Zyxel Certified Network Engineer Level 2 - Security Zyxel Certified Network Engineer Level 1 - Nebula
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    Hi @nielsscheldeman ,

    Because the SSL VPN service works perfectly initially and only fails after a few days—and is immediately recovered by simply disabling and re-enabling the feature—your configuration is likely correct. This behavior suggests a potential internal system state execution issue rather than a misconfiguration.
    The next time this issue occurs (before you disable/enable the service to fix it), please collect the diagnostic information and your current configuration file. This will help us analyze the state of the SSL VPN daemon when it stops responding. You can find instructions on how to collect these files here:

    How to collect diag-info from web GUI for USG FLEX H series? — Zyxel Community


    Please share these files or any sensitive details with us via private message by clicking my account > Message

    Zyxel_Judy

  • nielsscheldeman
    nielsscheldeman image  Ally Member
    First Comment Friend Collector Fourth Anniversary
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    So an update after long time. We saw that our Userlock service behind the Radius server got millions of login attempts from 1 client through the VPN. After resetting that service/client , the VPN Service didn't crash anymore.

    But it's strange that a client can try to connect so many times to the VPN Service? Why isn't that blocked?

  • nielsscheldeman
    nielsscheldeman image  Ally Member
    First Comment Friend Collector Fourth Anniversary
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    Spoke to soon :) Problem happened again, sent you private message.

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