[USG FLEX 100H] IP Reserved on local DHCP Server and NULL as HostName in the DHCP Log

Maverick87
Maverick87 Posts: 8  Freshman Member
First Comment Friend Collector
in USG FLEX H Series

Hello everyone,

I have a problem into DHCP Log section.
When a device with IP reservation try to obtain an IP from the interface's DHCP Servers, into the log appear the HostName as "(NULL)".

For Example:
DHCP server assigned 192.168.0.21 to (null)(AB:CD:EF:GH xxxx)
DHCP server assigned 192.168.0.8 to (null)(AB:CD:EF:GH xxxx)
DHCP server offered 172.16.2.200 to (null)(AB:CD:EF:GH xxxx)

Thank you so much,
Valerio

All Replies

  • PeterUK
    PeterUK Posts: 4,005  Guru Member
    100 Answers 2500 Comments Friend Collector Seventh Anniversary
    edited September 4

    Yes odd how when not Reserved it logs hostname then when Reserved guess its a code decision so that when DHCP comes in it 1st says is this MAC listed in Reserved if yes give that MAC this IP but simply does not pull the hostname of the DHCP for the logs and if DHCP in does not match MAC listed in Reserved it follows other decisions and pulls hostname for the logs.

  • Maverick87
    Maverick87 Posts: 8  Freshman Member
    First Comment Friend Collector

    YES, when is not reserved, the HostName is visibile correctly.

    Sure, that is a code decision, but the HostName is known, also in the DHCP Reserved list, so you can choice to get the "newest" hostname from the reserved list, or you can keep the original hostname taken it directly from the device (when you reserve an IP you can specify also the hostname).

    Another… into the DHCP Reserve list, is not possible to have 2 equal hostname, but if the devices is not ip reserved, can be present 2 same hostname (obviously the MAC Address is different)

    So please, can review the code for allow 2+ equal hostname and report the correct hostname into the DHCP log?

  • Zyxel_Tina
    Zyxel_Tina Posts: 193  Zyxel Employee
    Zyxel Certified Network Administrator - Security Zyxel Certified Network Administrator - Switch 50 Answers First Comment

    Hi @Maverick87,

    We have reproduced the behavior you described on our USG FLEX 100H, where a device with a DHCP reservation is logged with a (NULL) hostname.

    The issue has been escalated for further investigation to determine the root cause and will require some time to clarify. We will provide an update as soon as we have any new information.

    Regarding your second question,

    into the DHCP Reserve list, is not possible to have 2 equal hostname, but if the devices is not ip reserved, can be present 2 same hostname (obviously the MAC Address is different)

    could you please provide a screenshot so we can better understand the problem?

    Thank you for your patience and cooperation.

    Zyxel Tina

  • PeterUK
    PeterUK Posts: 4,005  Guru Member
    100 Answers 2500 Comments Friend Collector Seventh Anniversary
    edited 10:43AM

    The hostname thing is a known issue you can have two different MAC's with the same hostname the FLEX does not use the hostname when assigning IP's when you want to reserved two devices with the same hostname you can add one with a new name not that this changes to the devices hostname.

    Screenshot 2025-09-05 112555.png

    you then reserve one

    Screenshot 2025-09-05 113023.png

    then reserve the other but that cause the other to be lost

    Screenshot 2025-09-05 113052.png

    Then DHCP happens and you see both

    Screenshot 2025-09-05 113209.png

    then you have to unreserve the one not reserved to then add as with different hostname

    Screenshot 2025-09-05 113421.png
  • Maverick87
    Maverick87 Posts: 8  Freshman Member
    First Comment Friend Collector
    image.png

    I Have two Tuya smart LED driver device, use obviously different MAC Address (in which only the latest two octet change), and share the same hostname (wlan0).

    When I reserve the IP for this device, I cannot assign the same hostname for this two devices:

    image.png

    Same things for my Samsung Air Conditioner system. I have 4 internal Air Conditioner split, same model, different MAC Address but same HostName. Also in this case, I cannot add same hostname.

    The problem is present also for the assignment… the firewall not accept to distribute IP when the hostname is the same (but MAC Address is different), so only one device is accept for hostname and this is can be a problem, because I don't know how to assign the correct MAC Address to a different "named" hostname.

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