Probe into the relationship between switch tagged and untagged

when the port receives data:

If the port is tagged, when the packet itself does not contain a VLAN, the input packet is added to the default VLAN, and if the packet itself already contains a VLAN, it is no longer included.
In the case of the untagged method, all the input packets are added to the default VLAN. Regardless of whether the input packet already has a VLAN tag.

when the port sends data :
If the port is tagged, if the port default VLAN equals the VLAN of the packets sent, the VLAN tags are removed from the packets sent, and if not equal, the packets are sent out with VLANs to enable the VLAN to pass through.
In the case of untagged, the VLAN ID is removed from the packet, regardless of the port default VLAN, or whether it equals the VLAN of the packet to be output.

The Ethernet port has three types of links: Access, hybrid, and trunk. A port of type access can only belong to 1 VLANs, which is typically used to connect to a computer's port, a trunk-type port that belongs to multiple VLANs, a message that can receive and send multiple VLANs, and a port that is typically used for connections between switches; The port of type hybrid can belong to more than one VLAN. Messages that can receive and send multiple VLANs can be used for connections between switches, and can also be used to connect users ' computers. The difference between the hybrid port and the trunk port is that the hybrid port can allow multiple VLAN messages to be sent without tagging, while the trunk port allows only the default VLAN messages to be sent without tagging.

The trunk here is not the concept of port Gan Lu, i.e. port aggregation or link aggregation, but rather a concept that allows VLAN transmission. If you want to use port aggregation, see the related Port aggregation section.

It is important to note that:

L on an Ethernet switch, the trunk port and the hybrid port cannot be set at the same time.
L If a port is designated as a mirrored port, it can no longer be set to the trunk port and vice versa.
By default, the port is an access port.

The access port belongs to only 1 VLANs, so its default VLAN is its VLAN, not set, and the hybrid port and trunk port belong to multiple VLANs, so you need to set the default VLAN ID. If the default VLAN ID of the port is set, when the port receives a message without VLAN tag, the message is forwarded to the port belonging to the default VLAN, and when the port sends a message with VLAN tag, if the VLAN ID of the message is the same as the port default VLAN ID, The system will remove the VLAN Tag of the message and then send the message.

It is important to note that:

The Ltrunk port cannot be configured at the same time as Isolate-user-vlan, and the hybrid port can be configured simultaneously with Isolate-user-vlan. However, if the default VLAN is a mapped VLAN in Isolate-user-vlan, modifying the default VLAN ID is not allowed and can only be modified after de-mapping.

The default VLAN ID of the hybrid port or trunk port must be the same as the default VLAN ID of the hybrid port or trunk port of the connected peer switch, otherwise the message will not be transmitted correctly.

By default, the default VLAN for the hybrid port and trunk port is the VLAN 1,access port where the default VLAN belongs to itself.

Since each desktop switch is connected to a workstation belonging to VLAN1 and VLAN2, and the upper-connected port is only one, we need to set the "tagging" (Tagged) on the connection port of the switch and switch. The connection port for the server and workstation is not a label, so the connection port should be set to "untagged".

From for notes (Wiz)

Probe into the relationship between switch tagged and untagged