Implementations Of Qinq; Modifying The Tpid Value In A Vlan Tag - HP 6600 Configuration Manual

Figure 50 Single-tagged Ethernet frame header and double-tagged Ethernet frame header
The default maximum transmission unit (MTU) of an interface is 1500 bytes. The size of an outer VLAN
tag is 4 bytes. HP recommends you to increase the MTU of each interface on the service provider network
to at least 1504 bytes. For more information about interface MTU configuration, see Interface
Configuration Guide.

Implementations of QinQ

HP provides the following QinQ implementations:
Basic QinQ—Basic QinQ enables a port to tag any incoming frames with its PVID tag, regardless
•
of whether they have already been tagged. If an incoming frame has been tagged, it becomes a
double-tagged frame. If not, it becomes a frame tagged with the PVID tag.
• Selective QinQ—Selective QinQ is more flexible than basic QinQ. In addition to all the functions of
basic QinQ, selective QinQ enables a port to perform the following per-CVLAN actions for
incoming frames:
Tag frames from different CVLANs with different SVLAN tags.
Mark the outer VLAN 802.1p priority based on the existing inner VLAN 802.1p priority.
Modify the inner VLAN ID.
Besides being able to separate the service provider network from customer networks, selective
QinQ provides abundant service features and enables more flexible networking.

Modifying the TPID value in a VLAN tag

A VLAN tag uses the TPID field to identify the protocol type of the tag. The default value of this field, as
defined in IEEE 802.1Q, is 0x8100.
Figure 51 shows the 802.1Q-defined tag structure of an Ethernet frame.
Figure 51 VLAN tag structure of an Ethernet frame
144