Flex200 V5.42(ABUI.1) crashed this morning: after reset is back online but no WiFi clients

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GiuseppeR
GiuseppeR Posts: 759 image  Guru Member
Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Engineer Level 1 - Nebula 5 Answers First Comment
edited June 15 in Nebula

Hello everyone,

this morning a USG FLEX 200 with latest V5.42(ABUI.1) onboard crashed and it was unable to come back online with its entire network (7x Zyxel appliances):

immagine.png

As you can see it crashed multiple times:

immagine.png

I was just able to see it online but not the rest of the network (switches, APs, servers and so on…) because the firewall was unable to serve the DHCP server. It was able only to reboot itself via Nebula. Nothing else.

As you can see the offline issue was for the entire network:

immagine.png

So I had to go on site.

I tried to plug in a WAN2 to check if it was something related to the ISP connection, but the firewall was unable to get the WAN2 also when unplugging WAN1.

So I had to reset it.

After I reset it, it went online automatically (I set nothing, neither the ISP connection parameters and that is strange…) letting the rest of the network go online so the customer was able to work again.

The problem is that I cannot see the exact list of devices, linked to it, for example it does not show anything on WiFi while I'm sure that there are devices that goes wireless there (e.g. printers, a pair of tablets…):

immagine.png

As you can see here:

immagine.png

I have a PC too that is linked to that site WiFi, but zero devices on Nebula.

How can I understand what happened?

Someone else saw a similar behaviour?

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  • GiuseppeR
    GiuseppeR Posts: 759 image  Guru Member
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Engineer Level 1 - Nebula 5 Answers First Comment
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    EDIT.

    After almost half a day I start seeing again WiFi devices in my list:

    immagine.png

    Please compare this to my previous screenshot 😎

  • Zyxel_Melen
    Zyxel_Melen Posts: 4,941 image  Zyxel Employee
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate
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    Hi @GiuseppeR

    The device offline timestamp seems match the Nebula incident period.

    Nebula Cloud Service Incident 2026-06-15 09:52 - 17:53 (UTC+0) — Zyxel Community

    About the wireless client counts, I'm checking on it.

    Zyxel Melen


  • GiuseppeR
    GiuseppeR Posts: 759 image  Guru Member
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Engineer Level 1 - Nebula 5 Answers First Comment
    edited June 16
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    Hi @Zyxel_Melen

    I understand the fact that this issue seems to match the Incident period, but it is strange that the firewall took down the entire network: it was unable to release a dynamic IP also for my laptop when I went on site (the reason why I had to reset the firewall).

    The reality was that the client was NOT able to go online until I went there.

    When there is a Nebula Incident the difference is that you cannot reach Nebula services, but I was able to see that specific ORG down and on site they were unable to go outbound.

  • Zyxel_Melen
    Zyxel_Melen Posts: 4,941 image  Zyxel Employee
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate
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    Hi @GiuseppeR

    May I know some details when the issue happened?

    1. All clients can't access Internet or new connected clients? Are they wireless client or wired client?
    2. Does this site set any authentication/Captive portal with Nebula cloud authentication?

    If your network uses Nebula cloud authentication, that outage affecting the Nebula authentication server may prevent you from accessing the Internet, as the default captive portal policy blocks all traffic until sign-on is completed.

    If this is not your case, we might not check further since the issue was resolved by factory default.

    Zyxel Melen


  • GiuseppeR
    GiuseppeR Posts: 759 image  Guru Member
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Engineer Level 1 - Nebula 5 Answers First Comment
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    Hi @Zyxel_Melen

    here the answers:

    1- everything went down. No internet connection for wired and wireless devices. You can see my screenshots above but also the logs on Nebula, that is a Pro licensed ORG.

    I was unable to connect to internet too (when using my laptop linked to the front ports on the firewall itself, neither on the rest of the network using random ports).

    2- no captive portal, only Cloud authenticaton for a VPN user. I can understand that VPN could be a no go for the external user, but the rest of the network should stay alive without issues.

    It is also more strange the behaviour when I had to reset the firewall with a clip.

  • Zyxel_Melen
    Zyxel_Melen Posts: 4,941 image  Zyxel Employee
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate
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    Hi @GiuseppeR

    Thanks for the update. Could you help to enable Zyxel support access? I would like to ask our team to have further checks.

    Zyxel Melen


  • GiuseppeR
    GiuseppeR Posts: 759 image  Guru Member
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Engineer Level 1 - Nebula 5 Answers First Comment
    edited June 24
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    Hi @Zyxel_Melen

    done, sent a PM with screenshots and infos

  • Zyxel_Melen
    Zyxel_Melen Posts: 4,941 image  Zyxel Employee
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate
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    Hi @GiuseppeR

    About the crash/no Internet issue, I found the possible evidence for this issue and have a further investigation. I will update once I get further information.

    About the no WiFi clients on client page or dashboard, this is confirmed due to the 6/15 incident.

    - Monitoring information abnormal on NCC

    Sorry for delayed update in the incident post.

    Zyxel Melen


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