Pass the Huawei HCIE-Datacom H12-891_V1.0 Questions and answers with CertsForce

Understanding Telemetry Encoding Formats

????What is Telemetry?

Telemetry is a real-time network monitoring methodthat provideshigh-frequency data collection.

Used inAI-driven networks for predictive analytics and automation.

????Common Telemetry Encoding Formats:

✅GPB (Google Protocol Buffers)

Highly efficient binary formatthat reducesmessage size and CPU overhead.

Commonly used forhigh-speed, real-time analytics.

✅JSON (JavaScript Object Notation)

Human-readable format, widely used inRESTful APIs.

Less efficientthan GPB in high-speed telemetry buteasier to debug.

????Why is the Answer FALSE?

❌GPB is not mandatory; JSON can also be used in telemetry.

✅Huawei supports both GPB and JSON telemetry encoding formats.

Real-World Application:

Cloud Networking:UsesGPB for fast data collectionandJSON for API-based telemetry visualization.

AI-Driven Networks:High-speedAI analyticsleverageGPB encodingfor efficiency.

✅Reference:Huawei HCIE-Datacom Guide – Telemetry Encoding Formats and Data Collection

Let's dissect each option based on OSPFv3 LSA behavior from Huawei HCIE Datacom documentation.

✅ Option A: Correct

OSPFv3 uses Router LSAs (Type 1) to describe the local interfaces, links, and neighbors.

R1, as part of Area 0, will generate Router-LSAs and receive Router-LSAs from neighbors in the same area (R2 and R3 via switch S1).

Huawei Datacom Reference:

"Each OSPFv3 router originates a Type 1 Router LSA for each area it belongs to."

(Source: HCIE-Datacom Study Guide v3.0 - OSPFv3 Fundamentals)

❌ Option B: Incorrect (Correct Answer)

Link-LSAs (Type 8) are not sent between routers. They are only generated for each link on which the router has at least one neighbor. These LSAs are only flooded on the local link.

R1 cannot receive two Link-LSAs from R2 about both links. It can only receive the Link-LSA that R2 generates for the shared link with R1. The other link (e.g., to R4 in Area 1) is irrelevant to R1.

Huawei Datacom Reference:

"A Link LSA is generated by a router for each attached link and is sent only to the routers on the same link."

(Source: HCIE-Datacom Study Guide v3.0 - OSPFv3 LSA Types)

✅ Option C: Correct

On broadcast links, DRs generate Type 2 Network LSAs.

If R3 is the DR on the shared segment (with R1), R1 will have the Network-LSA from R3 in its LSDB.

Huawei Datacom Reference:

"The DR on a broadcast network generates a Type 2 Network LSA to describe all routers on that link."

(Source: HCIE-Datacom Study Guide v3.0 - OSPFv3 LSDB Construction)

✅ Option D: Correct

R2 connects Area 0 and Area 1, hence it's an ABR.

ABRs generate Type 3 Inter-Area-Prefix LSAs to advertise IPv6 prefixes from one area to another.

R2 advertises Area 1 prefixes to Area 0 routers (R1 and R3).

Huawei Datacom Reference:

"Inter-Area-Prefix LSAs (Type 3) are generated by ABRs to advertise IPv6 prefixes from one area into another."

(Source: HCIE-Datacom Study Guide v3.0 - ABR Functionality in OSPFv3)

Comprehensive and Detailed Explanation:

TheOSPF error outputshows:

✔Hello timer mismatch (1 error)→Hello intervals must match for adjacency formation(A)✅

✔No Netmask mismatch errors→Subnet masks are consistent, so option C is incorrect❌

✔No Extern option mismatch→No evidence of area type inconsistency (option D)❌

✔If area IDs were mismatched, adjacency would not form (option B is correct)✅

Thus, the correct answers areA and B.

????Reference:Huawei HCIE Datacom – OSPF Troubleshooting

Network migration typically includes the followingphases:

Preparation Phase:

Network survey

Migration plan design

Backup

Pre-configuration

Middle Phase (Migration Execution):

On-site monitoring

Migration implementation

Service test (to verify the migration effect)

Post-Migration Phase:

Optimization

Documentation

Final acceptance

Hence,Migration preparationis part of theinitial phase, not themiddle phase.

Correct answer: A. Migration preparation

Comprehensive and Detailed In-Depth Explanation:1. Understanding SRv6 (Segment Routing over IPv6):SRv6 uses theIPv6 headeralong with an additionalSRH (Segment Routing Header)to implement segment routing within an IPv6 network. The SRH contains:Segment List (SL):A list of IPv6 addresses (segments) to traverse.SL (Segments Left):An integer that indicates thenumber of segmentsyet to be visited.Active Segment:Thenext IPv6 addressin the segment list, stored in theDestination Addressfield of the IPv6 header.2. Analyzing the Given Scenario:Thesegment list (SL)in the SRH header shows:FC04::400FC04::4FC03::3The segment list is processed inreverse order(from bottom to top).SL (Segments Left)indicates theindex of the active segmentin the list.TheDestination Addressin the IPv6 header is currentlyFC04::4, indicating that theactive segmentis thesecond elementin the list.3. Determining the Value of SL:Theindexingin the segment list starts from0.SinceFC04::4is thesecond segment (from the bottom), the value ofSLwill be1.This means that1 segment is leftto be processed after the current one (FC04::4).Once the packet reachesFC04::4, theSL value will decrement to 0, and the next segment (FC03::3) will be processed.4. Why the Answer is 1:TheSL value decreases as segments are processed.As the currentactive segmentis thesecond in the list (from the bottom), theSL value is 1.

Understanding User Isolation in the Same VLAN

In a traditional VLAN,all devices within the same VLAN can communicateunless additional security policies are applied.To isolate users within the same VLAN, the following technologies can be used:

✅B. Port Isolation (Private VLAN or Layer 2 Isolation)

Prevents communication between ports within the same VLAN.

Common in enterprise and campus networksto improve security.

Example:Isolating guest users from employees within the same VLAN.

✅C. IPSG (IP Source Guard)

BlocksIP address spoofingwithin the same VLAN.

UsesDHCP snooping binding tableto verify whether a device is using anauthorized IP address.

✅D. Ethernet Port Security

Limits the number of MAC addressesallowed per port.

Preventsunauthorized devicesfrom communicating within the VLAN.

❌A. Super VLAN (Incorrect Choice)

Super VLANgroups multiple VLANs under a single Layer 3 gateway, but it doesnot provide isolationwithin the same VLAN.

Real-World Application:

Public Wi-Fi Networks:Ensures thatusers within the same VLAN cannot communicatewith each other.

Enterprise Security:Prevents unauthorized access or attacks withinshared VLANs.

✅Reference:Huawei HCIE-Datacom Guide – VLAN Security and User Isolation Technologies

Comprehensive and Detailed In-Depth Explanation:

WhenIS-ISis used as theIGP (Interior Gateway Protocol)to advertiseSegment Routing (SR) SIDs, theLevel-2 (L2) routeradvertisesnode SIDs globally across the entire IS-IS domain, not just within a single area.

Level-1 (L1) routersonly advertise within the local area, butL2 routersdistribute information across multiple areas, enabling inter-area reachability.

Therefore, the statement isFALSE.

TheMPLS headerconsists of:

Label (20 bits)– Label value used for forwarding.

EXP (3 bits)– QoS field (Class of Service).

S bit (1 bit)– Bottom-of-Stack indicator.

TTL (8 bits)–Time-to-Live, similar to the TTL field in the IP header.

Function of TTL in MPLS:

It is used toprevent infinite loops.

Every LSRdecrementsthe TTL by 1.

When TTL reaches0, the packet isdiscarded.

This mirrors the behavior of IP TTL and ensures loop prevention in MPLS networks.

Correct answer: D. This field is used to prevent packet forwarding loops, similar to the TTL field in an IP header.

X = 0

Y = 0

Z = 1

Understanding MPLS Label Headers

????What is MPLS (Multiprotocol Label Switching)?

MPLS is ahigh-performance forwarding technologythat replacesIP lookups with label switching.

Packets are forwardedbased on labels instead of destination IP addresses.

MPLS labels are stacked when passing throughmultiple hops.

????MPLS Label Stack Structure

Each MPLS label hasfour fields:

Label– 20-bit identifier used for forwarding.

EXP (Experimental Bits / Traffic Class)– 3-bit field used forQoS (Quality of Service).

S (Bottom of Stack)– 1-bit flag that indicates whether this is thelast (bottom) label in the stack.

TTL (Time-To-Live)– 8-bit field to prevent loops.

Understanding the EXP Fields (X, Y, Z) in the Figure

The image shows a packet with three MPLS labels.

Each label has anEXP field (X, Y, Z) representing the QoS bits.

By default,MPLS EXP bits are copied from the top label to lower labels unless modified by QoS policies.

If no QoS policy modifies the EXP bits, they remain thedefault value of 0.

Thebottom label in the stack (Label 3) often has an EXP value of 1 to indicate specific QoS policies.

Why Are the Answers X = 0, Y = 0, Z = 1?

✅X = 0 (Default EXP for Label 1, the top label in the stack).

✅Y = 0 (EXP for Label 2, unchanged from the default value).

✅Z = 1 (EXP for Label 3, indicating a QoS setting applied to the bottom label).

Real-World Application:

MPLS QoS (Quality of Service):EXP values determinepacket priorityinService Provider networks.

Traffic Engineering (TE):MPLS labels guide packets throughoptimized paths, ensuringlow-latency services.

Enterprise WAN Optimization:MPLS traffic is prioritized forcritical applications like VoIP, Video Conferencing, and Cloud Services.

✅Reference:Huawei HCIE-Datacom Guide – MPLS Label Stack and QoS EXP Field Processing

On the2.4 GHzband, onlythree non-overlapping channelsexist:1, 6, and 11.

Inhigh-density WLAN scenarios, channels like1, 5, 9, and 13can be used withlower transmit powerto reduce co-channel interference — though they slightly overlap, they can work in dense deployments when managed properly.

On the5 GHzband, there are many non-overlapping channels. It’s recommended tostagger high and low channelsamong adjacent APs toavoid interference.

Correct answer: A. TRUE