Introduction to the difference between tagged ports and untagged ports

The difference between Tagged ports and Untagged ports

In Ethernet switches, ports can be divided into Tagged ports and Untagged ports, and there are differences in their data processing methods.

Tagged Port

• The transmitted data frame contains a tag (tag), which is used to identify the VLAN (virtual LAN) to which the data frame belongs.
• When the data frame enters the switch from the Tagged port, the switch routes the data frame to the corresponding VLAN based on the tag information.
• When the data frame leaves the switch from the Tagged port, the switch retains the tag information in the data frame so that subsequent switches can continue to route the data frame.

Untagged port

• The transmitted data frame does not contain tags, so it can only belong to one VLAN.
• When a data frame enters the switch from the Untagged port, the switch assigns the data frame to the VLAN to which the port belongs by default.
• When the data frame leaves the switch from the Untagged port, the switch removes the tag information from the data frame.

Main Differences

##VLAN AssociationCan belong to multiple VLANsCan only belong to one VLANExchange processRoute to the specified VLANDefault Route to the VLAN to which the port belongsData frame modificationKeep tagDelete tag##Device Compatibility

Features	Tagged Port	Untagged Port
Tag	Contains	Does not contain
Need to support VLAN	No need to support VLAN

Usage scenarios

Tagged Port:
• Used to connect devices that support VLAN, such as routers, servers or other switches.
Untagged Port:
• Used to connect devices that do not support VLAN, such as PCs, printers, or IP phones.

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