Simple GS1900-24E Vlan Config Problem

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NotoriousCanary
NotoriousCanary Posts: 3 image  Freshman Member
First Comment
in Switch

I'm new to my Zyxel GS1900-24E router so I'm probably missing something simple, but I can't see the DHCP server on my second VLAN and can't figure out why - so any help appreciated.

I am trying to setup two VLANs on the router.

VLAN1 (Home) is the default VLAN with port members 1-20.

VLAN2(Office) is the only other VLAN with port members 1 and 21-24.

So Port 1 is the only port common to both VLANs.

The network hub and DHCP server are connected to Port 1, and Port 1 is enabled for VLAN trunking.

Because Port 1 is a member of both VLANS, I think this means that I should be able to serve DHCP addresses to devices connected to either VLANs, but it only works for devices attached to VLAN1 ports and not VLAN2 ports.

All ports are set for 'Ingress Checking'; all ports are set for 'Untagged' data.

What am I missing or doing wrong. Thanks for all help and pointers.

John W

All Replies

  • XiLeiHaLo
    XiLeiHaLo Posts: 12 image  Freshman Member
    First Comment First Answer Friend Collector Fourth Anniversary

    Hmm… I think the GS1900-24E is a switch rather than a router, and each switch port can only have a single PVID (native VLAN).

    You’ve already proved that your device obtained a DHCP address from port 1, so its PVID must be 1. Therefore, to obtain a DHCP address from VLAN 2, you need to change the port’s PVID to 2 for your end devices.

    A more advanced network setup that can meet your requirement would involve running a RADIUS server with 802.1X dynamic VLAN assignment on the switch. In this setup, the RADIUS server decides which VLAN each connected client belongs to. However, you will need to understand how to configure the appropriate rules on the RADIUS server."

  • Zyxel_Tina
    Zyxel_Tina Posts: 642 image  Zyxel Employee
    Zyxel Certified Network Administrator - Security Zyxel Certified Network Administrator - Switch 100 Answers 500 Comments
    edited December 2025

    Hi @NotoriousCanary,

    Welcome to the Zyxel Community!

    Here’s how to correctly configure your GS1900-24E to enable DHCP for both VLANs:

    1. Port 1 Configuration (Uplink/Trunk Port):
      • For Port 1, configure it as an untagged member of VLAN1 and a tagged member of VLAN2. This allows VLAN2 traffic, including DHCP requests, to pass through with its VLAN tag, while VLAN1 traffic remains untagged.
    2. PVID Settings for Client Ports:
      • For client ports 2-20 (VLAN1 Home), set their PVID to 1.
      • For client ports 21-24 (VLAN2 Office), set their PVID to 2.
      • Keep these ports configured to transmit Untagged data to end devices.

    Zyxel Tina

  • NotoriousCanary
    NotoriousCanary Posts: 3 image  Freshman Member
    First Comment

    Hi Zyxel Tina,

    Belated thanks for your help.

    DHCP is now being seen in both VLANs.

    But - I've tried your setup and find that a computer connected on a VLAN2 port has full access to a network disc connected to a VLAN1 port.

    I've tried turning on 'ingress checking' for all ports on both VLANs except for the shared Port 1, but that hasn't made a difference.

    I've also set the 'Management VLAN' to VLAN1, but it seems I can log from VLAN2 connected computers.

    So I think I am still missing something in the configuration that prevents communications between the two VLANS.

    Any help gratefully appreciated.

    Thanks

  • Zyxel_Tina
    Zyxel_Tina Posts: 642 image  Zyxel Employee
    Zyxel Certified Network Administrator - Security Zyxel Certified Network Administrator - Switch 100 Answers 500 Comments

    Hi @NotoriousCanary,

    Sorry for the late reply!

    To troubleshoot the VLAN1/VLAN2 communication issue, could you please confirm if the uplink router has any policies blocking traffic between VLAN1 and VLAN2?

    If no, add a blocking policy for VLAN1 ↔ VLAN2 traffic, then test again.

    If the issue still persists, please provide:

    • The device's current configuration file
    • Your network topology

    This will help us identify the next steps.

    Zyxel Tina

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