Describes the value of the 802.1ad Ethernet protocol type.
The Ethernet protocol type of the outer VLAN tag of a port can
be configured to dot1q or dot1ad. The value of dot1q is invariably 0x8100;
the value of dot1ad is configurable, but cannot be the values of
other standard protocols, such as 0x0806.
The default value of dot1ad is 0x88a8.
Range: 0x600-0xffff