Implementations Of Qinq; Modifying The Tpid In A Vlan Tag - HP 5120 EI Series Lan Switching Configuration Manual

Figure 60 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.

Implementations of QinQ

HP provides the following QinQ implementations: basic QinQ and selective QinQ.
Basic QinQ
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Basic QinQ enables a port to tag any incoming frames with its port VLAN ID (PVID) tag, regardless
of whether they have been tagged or not. 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.
Besides being able to separate the service provider network from the customer networks, selective
QinQ provides abundant service features and enables more flexible networking.

Modifying the TPID in a VLAN tag

A VLAN tag uses the tag protocol identifier (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 61 shows the 802.1Q-defined tag structure of an Ethernet frame.
Figure 61 VLAN tag structure of an Ethernet frame
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