Vlan Tagging - Siemens SCALANCE XB-200 Configuration Manual

To identify which packet belongs to which VLAN, the frame is expanded by 4 bytes (VLAN
tagging (Page 33)). This expansion includes not only the VLAN ID but also priority
information.
Options for the VLAN assignment
Each port of a device is assigned a VLAN ID (port-based VLAN). You configure port-based
VLAN in "Layer 2 > VLAN > Port-based VLAN (Page 185)".
4.6

VLAN tagging

Expansion of the Ethernet frames by four bytes
For CoS (Class of Service, frame priority) and VLAN (virtual network), the IEEE 802.1Q
standard defined the expansion of Ethernet frames by adding the VLAN tag.
Note
The VLAN tag increases the permitted total length of the frame from 1518 to 1522 bytes.
The end nodes on the networks must be checked to find out whether they can process this
length / this frame type. If this is not the case, only frames of the standard length may be
sent to these nodes.
The additional 4 bytes are located in the header of the Ethernet frame between the source
address and the Ethernet type / length field:
Figure 4-3 Structure of the expanded Ethernet frame
The additional bytes contain the tag protocol identifier (TPID) and the tag control information
(TCI).
SCALANCE XB-200/XC-200/XP-200 Web Based Management
Configuration Manual, 07/2016, C79000-G8976-C360-04
Technical basics
4.6 VLAN tagging
33