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    • Tagged or Untagged Port for a IP phone server

    Posts: 25  Freshman Member
    First Comment Second Anniversary
    in Switch

    Hi all,

    My office has a NEC SL2100 phone system, and we have created a VLAN (VLAN ID=2) for it.

    All IP phone are at tagged port and the phone server is at a untagged port with PVID=2. And this server's port is excluded/prohibited from all other VLANs.

    I found that the phone cannot connect to its server if I change the server's port from untagged to tagged. I am just so curious that why the connection will only work when server's port is untagged. I thought it will work no matter it is a tagged or untagged port.

    Could anyone clarify this for me?

    Thank you very much.

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    • Posts: 2,993  Zyxel Employee
      Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate

      Hi @YiHsien,

      According to your result I found that the phone cannot connect to its server if I change the server's port from untagged to tagged, It seems your server is a VLAN-aware device that has a VLAN 2 interface. If the server receives a packet without a VLAN tag, it will not be sent to VLAN 2 interface but to another interface without VLAN.

      Zyxel Melen


    • Posts: 25  Freshman Member
      First Comment Second Anniversary

      Thanks Melen,

      Our server works with untagged port.

      I am confused that why a a VLAN-aware device will only work under a untagged port? (it doesn't work under a tagged port)

      Thanks again.

    • Posts: 2,993  Zyxel Employee
      Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate

      Hi @YiHsien,

      Please allow me to rephrase my previous explanation since I misinterpreted your description. Since your phone can reach the phone server when the switch port is untagged, this seems your server is a VLAN-unaware device. When it receives a packet with a VLAN tag, it will ignore this packet. If you want the phone server to handle the VLAN tag packet, the server's NIC needs to support VLAN.

      Zyxel Melen


    • Posts: 25  Freshman Member
      First Comment Second Anniversary

      Hi Melan,

      Thank you for reply.

      Do you mean since the server is a VLAN-unaware device, it can only be connected to a untagged port (because if it receives a packet with a VLAN tag, that packet will be ignored so the connection will fail)?

    • Posts: 2,993  Zyxel Employee
      Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate

      Hi @YiHsien,

      Yes, the server seems like a VLAN-unaware device, so, it can only be connected to an untagged port.

      Zyxel Melen


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