Which of the following enables service providers to support multiple customers with the same VLAN ID over the same backbone?

VLAN Stacking, also known as Q-in-Q tunneling, is a technology that allows multiple customers to

use overlapping VLAN IDs while being transported over a shared service provider network.

Key Concepts:

Customer VLAN (C-VLAN): The VLAN used by the customer in their own network.

Service VLAN (S-VLAN): The VLAN used by the service provider to encapsulate the customer VLAN.

When VLAN stacking is applied:

A customer's Ethernet frame already tagged with a C-VLAN is encapsulated with an additional outer

S-VLAN tag.

This way, multiple customers can use the same C-VLAN ID, but remain isolated by the unique S-VLAN

assigned to them by the service provider.

Why Other Options Are Incorrect:

A . VLAN Trunking: Used to carry multiple VLANs over a single physical link but doesn’t allow reuse of

VLAN IDs across customers.

C . VLAN Tagging: Refers to the general process of adding a VLAN tag; it doesn't provide the isolation

needed across shared infrastructure.

D . VLAN Routing: Refers to Layer 3 routing between VLANs, not to ID reuse or transport over a

shared provider backbone.

Reference:

Nokia Service Architecture and VPNs Study Guide – Section: “Q-in-Q VLAN Stacking”

IEEE 802.1ad Standard – Provider Bridges (Q-in-Q)