Bumper start with V1.40 and DHCP server spamming

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PeterUK
PeterUK Posts: 4,796
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edited October 19 in USG FLEX H Series

So not sure what want down with this version but at first was there was DHCP with SFP problems after the upgrade but interestingly was resolved after pulling the power for a cold start.

As for the DHCP server spamming I have the FLEX 200H and 700H link by XGS1250-12 so

FLEX 700H GE11 192.168.177.1/24 DHCP server to port 4 XGS1250-12 and port 5 to 200H GE3 WAN
monitoring was done by port 7 for port 4 on the XGS1250-12

Sometimes when you plug 200H GE3 wait a bit then plug it back in causes spamming of DHCP

Screenshot 2026-10-19 151750.png

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  • Zyxel_Judy
    Zyxel_Judy Posts: 2,789
    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 @PeterUK ,

    We tried to reproduce the same scenario on our side, but in our local test the DHCP process behaved normally — we did not see any spamming.

    Since we couldn’t reproduce the issue locally, could you help us with a bit more detail so we can dig further? Specifically:

    • The full network topology (beyond what you’ve already shared, if there’s anything else relevant — e.g., other devices/VLANs involved)
    • The current configuration settings on both the USG FLEX 700H and the USG FLEX 200H (a configuration export from each would be ideal)
    • A packet capture taken while reproducing the spamming

    Zyxel_Judy

  • PeterUK
    PeterUK Posts: 4,796
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    hi Judy

    It should be a simple test to see this can I ask how you  packet capture your end? how many times did you test?

  • PeterUK
    PeterUK Posts: 4,796
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    edited October 21
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    Hmmm....seem the bumpy start problem is back on reboot something the FLEX 200H can get a IP needing the FLEX700H firewall to be turned off for FLEX 200H to get a IP other times it works. There dose seem to be a link to the cause if SFP if connected as DHCP client but unclear.

    PM sent

  • Zyxel_Judy
    Zyxel_Judy Posts: 2,789
    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 @PeterUK ,

    I tried this several times

    image.png

    P/S: We’ve received your files. We’ll review them and let you know if we find anything.

    Zyxel_Judy

  • PeterUK
    PeterUK Posts: 4,796
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    edited October 21
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    Ok and as of now I have found a workaround for not getting a IP for the DHCP server by this rule on the FLEX 700H

    Screenshot 2026-10-21 072126.png

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