Tagged or Untagged Port for a IP phone server

YiHsien

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.

Zyxel_Melen

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.

YiHsien

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.

Zyxel_Melen

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.

YiHsien

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)?

Zyxel_Melen

Hi @YiHsien,

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