Free 400-007 Questions Attempt

The hierarchical model provides:

A: Fault isolation by limiting failures to specific layers.

D: Modularity and flexibility, making it easier to implement changes without affecting the entire network.

Why other options are incorrect:

B: Design typically starts at the access layer upwards.

C: Server access is handled at the distribution or access layer, not the core.

E: Security is handled at access/distribution layers, not primarily at core layer.

Route Distinguishers (RDs) are fundamental to MPLS Layer 3 VPN architecture (RFC 4364). They allow the service provider to distinguish identical IP prefixes from different VPN customers by adding a unique identifier to each VPN route, preventing conflicts from overlapping IP spaces.

Unique RDs ensure that the VPNv4 address family maintains separation of identical customer prefixes.

Why other options are incorrect:

B: Route Targets control route import/export policy but do not differentiate overlapping prefixes.

C: NAT is not required inside MPLS VPN for overlapping IPs.

D: VRF IDs are local identifiers on routers; not relevant for prefix uniqueness in control plane.

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A (Policy-based routing):Allows classification of traffic based on source, destination, or protocol and applies forwarding policies accordingly, such as sending VoIP over MPLS and best-effort traffic over either link. PBR operates in fast-path switching modes to avoid process switching if properly configured.

Other options explained:

B: Virtual links relate to OSPF, not traffic steering.

C: Visualization is not a network forwarding technology.

D: Floating static routes select one link for all traffic, not per-traffic-type control.