Huawei Updated H12-891_V1.0 Exam Questions and Answers by indy

Comprehensive and Detailed Explanation:

✔ In Huawei CloudCampus public cloud, devices can be pre-registered using the Huawei Registration Query Center, eliminating the need for DHCP Option 148.

✔ How it works:

Devices contact the registration query center (via pre-configured serial numbers).

Query center provides controller information, allowing automatic onboarding.

No need for DHCP Option 148, which is normally used to provide controller addresses manually.

Thus, the statement is TRUE.

???? Reference: Huawei HCIE Datacom – CloudCampus Public Cloud Deployment

Comprehensive and Detailed Explanation:

✔ BIER vs. PIM Multicast Routing:

BIER (Bit Index Explicit Replication) eliminates the need for multicast distribution trees (MDTs) by encoding receiver information into the packet header.

PIM (Protocol Independent Multicast) requires MDTs to manage multicast forwarding paths.

✔ Correct Statements:✅ (A) BIER uses a Bitstring field in packet headers for forwarding.✅ (B) PIM builds MDTs to define multicast paths.✅ (C) BIER does NOT require MDTs, making it more scalable.

❌ (D) Incorrect → BIER does not require hop-by-hop join messages.

???? Reference: Huawei HCIE Datacom – BIER and PIM Comparison

From the IS-IS error output, the key error is:

Mismatched Area Addr(L1): 13

This clearly indicates that the area addresses are different, which prevents the Level-1 adjacency from forming.

Why is Option D Correct?

IS-IS Level-1 routers must have the same area ID to form an adjacency.

Since the log shows a mismatched area address, the adjacency fails at Level-1.

If R3 and R4 were Level-2 routers, they could form an adjacency even with different area IDs.

Why Are the Other Options Incorrect?

❌ Option A: No authentication failure is reported.❌ Option B: No "Mismatched Level" errors appear, so their levels are compatible.❌ Option C: No "Bad Circuit Type" errors indicate mismatched circuit types.

Thus, the correct answer is D.

???? Reference: Huawei HCIE Datacom – IS-IS Neighbor Troubleshooting

VRRP (Virtual Router Redundancy Protocol) and Flapping

VRRP ensures gateway redundancy by allowing multiple routers to work together as a virtual router. Flapping occurs when the master and backup routers frequently switch roles.

Causes of VRRP Flapping:

✅ A. Too small interval between Advertisement packet transmissions – Can cause flapping

If the Advertisement interval is too short, frequent VRRP state changes can occur.

✅ C. Packet loss on an interface of the backup device – Can cause flapping

If the backup router loses VRRP packets, it might assume the master is down and initiate an election.

✅ D. Flapping on the link transmitting VRRP Advertisement packets – Can cause flapping

If the link used for VRRP experiences instability, packets may be lost, triggering VRRP role changes.

Incorrect Answer Explanation:

❌ B. Inconsistent preemption delay settings – Does NOT cause VRRP flapping

Preemption delay only affects when a router takes over as master after recovering from a failure.

It does not directly cause flapping because the role change happens only after a delay, preventing frequent transitions.

Reference from Huawei HCIE-Datacom Documentation:

Huawei VRRP Configuration Guide – Preventing VRRP Flapping

HCIE-Datacom Study Material – VRRP Timers and Stability