Huawei H12-891_V1.0 Exam With Confidence Using Practice Dumps

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.

In OSPFv3 (used for IPv6), Link LSAs (Type 8) are not advertised throughout the entire area. Instead, they are only advertised on a specific link (i.e., the local link). This differs from OSPFv2, where LSAs like Type 1 or Type 2 are advertised across the area.

Exact Extract - Huawei HCIE-Datacom V1.0 Courseware - Chapter: OSPFv3 Operation

“Link LSAs are generated by routers for each attached link and sent only on that link, not flooded throughout the area.”

Comprehensive and Detailed In-Depth Explanation:

In the inter-AS MPLS VPN Option B solution:

Option B establishes a multi-hop eBGP connection between the ASBRs (ASBR-PE1 and ASBR-PE2) to exchange VPNv4 routes.

In this setup, the ASBRs exchange labeled VPNv4 routes via MP-BGP (Multiprotocol BGP).

The command:

[ASBR-PE1-bgp-af-vpnv4] undo peer 10.0.34.4 enable

is used to disable VPNv4 route exchange between the ASBR-PE1 and ASBR-PE2.

If this command is executed, ASBR-PE1 will not transmit VPNv4 routes to ASBR-PE2, breaking the inter-AS VPN connectivity.

Therefore, the statement is FALSE because ASBR-PE1 and ASBR-PE2 must exchange VPNv4 routes to maintain connectivity between the VPN sites across different ASes.