H12-891_V1.0 Exam Dumps : HCIE-Datacom V1.0

In MPLS LDP, there are two types of sessions:

Direct LDP sessions: Established between directly connected LSRs using LDP Hellos over a link.

Remote LDP sessions (also called targeted LDP sessions): Established between non-directly connected LSRs. These require manual configuration of the remote peer.

In this scenario, SWA and SWC are not directly connected, so a remote (targeted) LDP session must be set up.

For a remote LDP session:

You must configure the remote peer using the command:

[SWA-MPLS-LDP] targeted-peer x.x.x.x

Where x.x.x.x is the LSR ID of SWC (33.3.3.3 in this case).

The current configuration does not include this required step.

Thus, the correct statement is:

D. You need to create a remote peer and specify an LSR ID for the remote peer.

Understanding MPLS Forwarding Mechanism

MPLS (Multiprotocol Label Switching) is a high-performance forwarding mechanism that operates on two planes:

1️⃣ Control Plane:

Establishes Label Switched Paths (LSPs) using protocols like LDP (Label Distribution Protocol), RSVP-TE (Resource Reservation Protocol - Traffic Engineering), or BGP-LU (BGP Label Unicast).

Assigns labels to packets based on routing policies.

2️⃣ Data Plane (Forwarding Plane):

Uses a Label Forwarding Information Base (LFIB) instead of traditional IP routing.

Packets are forwarded based on labels, not IP addresses.

Analysis of the Answer Choices

✅ C. The system automatically assigns an ID to the upper-layer application that uses a tunnel. This ID is also called the tunnel ID.

Correct: MPLS assigns a Tunnel ID to applications that utilize tunnels (e.g., VPNs, MPLS-TE, or L2/L3 services).

This ID helps differentiate between various tunnel applications, ensuring traffic follows the correct LSP.

❌ A. After an IP packet enters an MPLS domain, the MPLS device forwards the packet based on FIB table queries.

Incorrect: MPLS routers do NOT use the FIB (Forwarding Information Base) for forwarding once labels are assigned.

Instead, they use LFIB (Label Forwarding Information Base) to switch packets based on labels.

❌ B. If the tunnel ID is 0x0, the MPLS forwarding process starts.

Incorrect: If the Tunnel ID is 0x0, MPLS does NOT start; it means no label is assigned, and traditional IP forwarding occurs.

❌ D. If the tunnel ID is not 0x0, the normal IP forwarding process starts.

Incorrect: If the Tunnel ID is not 0x0, MPLS forwards traffic using label switching, not IP forwarding.

Comprehensive and Detailed In-Depth Explanation:

During a network migration test, it is crucial not only to verify that the network itself is functioning correctly but also to ensure that upper-layer application services are running properly on the newly migrated network. Migration testing aims to confirm that the transition has not disrupted service functionality.

Option A and C focus solely on network performance, which is necessary but insufficient.

Option B refers to command outputs, which are technical checks and do not guarantee service continuity.

Option D correctly identifies that successful migration is indicated by proper operation of upper-layer application services, as the primary purpose of a network is to support these applications.