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Rockwell Automation Publication 1783-UM007I-EN-P - December 2017
Chapter 3
Configure Switch Features
VLAN 0 Priority Tagging
VLAN 0 priority tagging enables 802.1Q Ethernet frames to be transmitted
with the VLAN ID set to zero. For example, you can use this feature to forward
PROFINET traffic through the switch. These frames are called priority tagged
frames. Setting the VLAN ID tag to zero allows the VLAN ID tag to be
ignored and the Ethernet frame to be processed according to the priority
configured in the 802.1P bits of the 802.1Q Ethernet frame header.
802.1Q Tagging
The 802.1Q standard defines a system of VLAN tagging for Ethernet frames
and also contains a provision for a Quality of Service (QoS) prioritization
scheme known as 802.1P, which indicates the priority level of the frame. The
802.1Q standard adds this information to the Ethernet header, as shown in the
figure below. The priority level values range from zero (best effort) to seven
(highest). These values can be used to prioritize different classes of traffic. The
VLAN ID tag specifies the VLAN to which the frame belongs. The priority
bits define the priority with which the frames are processed.
Native VLANs
When a particular VLAN ID is assigned as a native VLAN on an Ethernet
interface, frames in the native VLAN transmitted from the Ethernet interface
are not tagged. Similarly, any untagged frames received on the Ethernet
interface are associated with the native VLAN on that interface. The Ethernet
interface can still receive both tagged and untagged frames. The tagged frames
are associated with the VLAN ID in the 802.1Q header (see above). Untagged
frames do not contain priority bits in the Ethernet frame header and are treated
as best effort. On ingress, Ethernet packets tagged with VLAN 0 are associated
with the native VLAN of the interface.
Destination Address
Source Address
Type/Length
802.1p bits
VLAN-ID
Type/Length
802.1Q Ethernet Frame
Type (0x8100)
Priority bits (0…7)
VLAN-ID (0)
802.1Q header
Summary of Contents for armorstratix 5700
Page 10: ...10 Rockwell Automation Publication 1783 UM007I EN P December 2017 Table of Contents Notes ...
Page 12: ...12 Rockwell Automation Publication 1783 UM007I EN P December 2017 Preface Notes ...
Page 72: ...72 Rockwell Automation Publication 1783 UM007I EN P December 2017 Chapter 2 Get Started Notes ...
Page 396: ...396 Rockwell Automation Publication 1783 UM007I EN P December 2017 Appendix A DataTypes Notes ...
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