Support for handling routers that do not provide DHCP servers(Organization:NewLadyHill Sapa Resort))

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duythượng
duythượng Posts: 7  Freshman Member
First Comment Friend Collector
in Nebula

hello.
currently i can not get IP from router please help me to fix it.

image.png

i tried to change lease time parameter.

image.png

my device can get IP but after lease time that i set the device can not get IP anymore. please help me to fix the error.
thanks team

All Replies

  • Zyxel_Judy
    Zyxel_Judy Posts: 2,317  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

    Hi @duythượng ,

    When clients can't obtain IP addresses after lease expiry, it's typically due to DHCP pool exhaustion.
    Please calculate the number of clients on this interface and verify that your DHCP pool is sufficiently sized for all devices.
    Since your network is deployed in a hotel environment, we recommend reducing the lease time from 2 days to 4-6 hours (maximum 8 hours). This shorter lease time will free up IP addresses more quickly when guests check out.

    Zyxel_Judy

  • duythượng
    duythượng Posts: 7  Freshman Member
    First Comment Friend Collector

    hi @zyxel_Judy
    thank you for your response.
    I have tried following your instructions.

    image.png

    but now my device still cannot obtain an IP ( VLAN is currently not assigning the IP currently in use to the TV )
    my TV has obtained the following IP and cannot connect to the network

    de9b0edc2542911cc853.jpg


    please help me to resolve this.
    Thank you very much.

  • Zyxel_Judy
    Zyxel_Judy Posts: 2,317  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

    Hi @duythượng ,

    To better support you, please capture network packets so we can analyze the DHCP process. Follow these steps:

    Packet Capture Instructions:

    1. Setup: On one available port of XGS1930-28 (MAC: BC:CF:4F:DA:90:0C) - the same switch where the problematic TV (MAC: e0:03:6b:14:8d:2d) is connected, configure access VLAN PVID 20
    2. Open Wireshark on your laptop and select the Ethernet interface
    3. Connect your laptop to switch mentioned in step 1
    4. Wait 1-2 minutes to capture sufficient traffic
    5. Share the packet capture file with us for analysis

    This will help us identify any issues in the DHCP negotiation process.

    Zyxel_Judy

  • Zyxel_Judy
    Zyxel_Judy Posts: 2,317  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
    edited June 18

    Hi @duythượng ,

    Thank you for sharing the packet file for our analysis.

    After reviewing the capture, we found that there is another DHCP server (Juniper network device) providing IP addresses for VLAN 20 clients, in addition to the USG FLEX 700. After adding an ACL to block DHCP responses from the Juniper network device, the TV was able to obtain an IP address from the USG FLEX 700 as expected.

    Zyxel_Judy

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