4A0-105 practice question 8 of 25

If a management VPLS is administratively disabled what will be the status of the associated user VPLS SAPs?

Full set: 156 questions
Answer options
A: Regular semantics will apply. It will be as if the SAP doesn't belong to a management VPLS.
B: All user VPLS SAPs will be disabled/pruned. Correct answer
C: It is not possible to administratively disable a management VPLS.
D: Spanning tree will be automatically enabled on the user VPLS SAPs.
Correct Answer:
B. All user VPLS SAPs will be disabled/pruned.
Explanation

In a Hierarchical VPLS (H-VPLS) model, the management VPLS (M-VPLS) provides the core transport mesh for multiple user VPLS instances. The operational state of a user VPLS and its components, such as Service Access Points (SAPs), is directly dependent on the state of the M-VPLS to which it is bound. When a management VPLS is administratively disabled (shutdown), it becomes operationally down. This action severs the transport path for all associated user VPLS services. Consequently, the system brings down (disables/prunes) all SAPs on those user VPLS instances to prevent traffic from being accepted and subsequently dropped (black-holed), ensuring consistent state propagation to the customer edge.

Why Incorrect

A. The SAP's operational state is directly dependent on the M-VPLS; it cannot operate as if the hierarchical dependency does not exist.
C. It is a standard operational capability to administratively disable any service, including an M-VPLS, for maintenance or policy enforcement.
D. Spanning Tree is a loop prevention protocol; its activation is not a direct consequence of an administrative shutdown of the VPLS transport service.

References

1. Nokia 7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 2 Services and EVPN Guide, Release 21.10.R1, Document Part Number: 3HE 17275 AAAD TQZZA, Section: "Hierarchical VPLS". This section describes the dependency of spoke-SDPs (connecting user VPLS) on the mesh-SDPs of the management VPLS. The operational state of the user service components relies on the operational state of the M-VPLS.

2. Nokia 7450 ESS, 7750 SR, 7950 XRS, and VSR Basic System Configuration Guide, Release 21.10.R1, Document Part Number: 3HE 17270 AAAD TQZZA, Section: "Administrative and Operational Status". This guide explains that an administrative shutdown command on any entity forces its operational state to down, which cascades to dependent entities.

3. Nokia 4A0-105 Courseware, Module 3: Virtual Private LAN Service (VPLS), Section: "Hierarchical VPLS (H-VPLS)". The official course material explains that the user VPLS (also called a spoke VPLS) relies entirely on the management VPLS for transport. A failure or shutdown of the M-VPLS results in a loss of connectivity for the user VPLS, leading to its SAPs becoming operationally down.

Scroll to Top