In an MPLS network, there are different types of operations for labels, among which the meaning of the "pop" action is?

A company consists of a head office and two branch offices, and uses MPLS VPN technology to transmit private network routes. In the networking mode of HuB&Spoke. Branches can only send and receive routes to and from the head office, and branches cannot directly send and receive routes to each other. In order to achieve the above requirements, which of the following schemes can the setting of RT be?

In the DU label distribution mode, if the Liberal retention mode is adopted, the device will retain the labels distributed by all LDP peers, regardless of whether the LDP peer is the optimal next hop to the destination network segment.

According to the configuration shown in the figure below, you can know that how many interfaces of R4 are advertised into IS-IS?

Qing technology is a technology that expands the VLAN space. It achieves the function of expanding the VLAN space by adding a layer of 8D2.1Q Tag on the basis of the 8Q2.12 tag message.
Which of the following statements about qinq is wrong?