VLAN Tagué / Non Tagué / PVID
Steve
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brupala Posted messages 111985 Registration date Status Membre Last intervention -
brupala Posted messages 111985 Registration date Status Membre Last intervention -
Hello,
I am working on the manual of a TPLink switch and I need advice on VLAN management.
Here is what I see in this manual:
(1) Untagged: The untagged port can be added to multiple VLANs. If a VLAN-tagged packet
arrives at a port and the VLAN ID in its VLAN tag does not match any of the VLANs the
ingress port belongs to, this packet will be dropped. The packets forwarded by the
untagged port are untagged.
(2) Tagged: The tagged port can be added to multiple VLANs. If a VLAN-tagged packet
arrives at a port and the VLAN ID in its VLAN tag does not match any of the VLANs the
ingress port belongs to, this packet will be dropped. When the VLAN-tagged packets are
forwarded by the tagged port, its VLAN tag will not be changed.
(3) PVID: (Port VLAN ID) is the default VID of the port. When the switch receives an un-VLAN-tagged
packet, it will add a VLAN tag to the packet according to the PVID of its received port and forward
the packets.
By creating a VLAN, we designate the ports of it with the notion of Tagged or Untagged. But that is not enough to allow devices within the same VLAN port range to communicate; the PVID must also be set on another page of the interface.
So, I understand this:
Vlan1=id 1
Vlan2=id 2
Vlan3=id 3
Non-tagged PC -> Switch port with PVID 1 and Untagged 1 + 2 + 3 => packet retransmitted: id 1
Non-tagged PC -> Switch port with PVID 1 and Tagged 1 + 2 + 3 => packet retransmitted: id 1
Tagged PC id 2 -> Switch port with PVID 1 and Untagged 1 + 2 + 3 => frame retransmitted: id 1
Tagged PC id 3 -> Switch port with PVID 1 and Untagged 1 + 2 + 3 => frame retransmitted: id 3
And for the other configurations, it's blocked.
Do you agree?
Thank you
Configuration: Windows / Chrome 51.0.2704.84
I am working on the manual of a TPLink switch and I need advice on VLAN management.
Here is what I see in this manual:
(1) Untagged: The untagged port can be added to multiple VLANs. If a VLAN-tagged packet
arrives at a port and the VLAN ID in its VLAN tag does not match any of the VLANs the
ingress port belongs to, this packet will be dropped. The packets forwarded by the
untagged port are untagged.
(2) Tagged: The tagged port can be added to multiple VLANs. If a VLAN-tagged packet
arrives at a port and the VLAN ID in its VLAN tag does not match any of the VLANs the
ingress port belongs to, this packet will be dropped. When the VLAN-tagged packets are
forwarded by the tagged port, its VLAN tag will not be changed.
(3) PVID: (Port VLAN ID) is the default VID of the port. When the switch receives an un-VLAN-tagged
packet, it will add a VLAN tag to the packet according to the PVID of its received port and forward
the packets.
By creating a VLAN, we designate the ports of it with the notion of Tagged or Untagged. But that is not enough to allow devices within the same VLAN port range to communicate; the PVID must also be set on another page of the interface.
So, I understand this:
Vlan1=id 1
Vlan2=id 2
Vlan3=id 3
Non-tagged PC -> Switch port with PVID 1 and Untagged 1 + 2 + 3 => packet retransmitted: id 1
Non-tagged PC -> Switch port with PVID 1 and Tagged 1 + 2 + 3 => packet retransmitted: id 1
Tagged PC id 2 -> Switch port with PVID 1 and Untagged 1 + 2 + 3 => frame retransmitted: id 1
Tagged PC id 3 -> Switch port with PVID 1 and Untagged 1 + 2 + 3 => frame retransmitted: id 3
And for the other configurations, it's blocked.
Do you agree?
Thank you
Configuration: Windows / Chrome 51.0.2704.84
1 réponse
Hi,
TPlink seems to be redefining the concepts of PVID and untagged VLAN.
In principle, PVIDs only concern untagged frames; tagged frames shouldn't change VLANs.
If the tagged VLAN is not valid on the port, it's normal for the frame to be dropped.
An untagged frame should exclusively take the PVID.
Tagged PC id 2 -> Switch port with PVID 1 and Untagged 1 + 2 + 3=> retransmitted frame: id 1
This shouldn't exist; the frame should remain in VLAN 2
and ... There you go!
TPlink seems to be redefining the concepts of PVID and untagged VLAN.
In principle, PVIDs only concern untagged frames; tagged frames shouldn't change VLANs.
If the tagged VLAN is not valid on the port, it's normal for the frame to be dropped.
An untagged frame should exclusively take the PVID.
Tagged PC id 2 -> Switch port with PVID 1 and Untagged 1 + 2 + 3=> retransmitted frame: id 1
This shouldn't exist; the frame should remain in VLAN 2
and ... There you go!
I've already seen the notions of tplink on the netgear brand.
It’s not a reason to change the VLAN number without notice, even if it’s internal.
Either we drop the frame, or we let it pass with its VLAN.
The conversion of the VLAN tag must be explicit on a port.
When we want to modify a VLAN number, we rather transport it in QinQ.