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

✅ Hypertext Transfer Protocol (HTTP) is an application-layer protocol used for:

Accessing web pages and hypermedia content.

Client-server communication over the internet.

Stateless communication with request-response architecture.

Key Features of HTTP:

Application Layer Protocol in the TCP/IP model.

Uses TCP (Port 80) and HTTPS (Port 443) for secure communication.

Supports REST APIs, web applications, and cloud services.

Reference from Huawei HCIE-Datacom Documentation:

Huawei Network Protocol Guide – HTTP and Web Services

HCIE-Datacom Study Material – Application Layer Protocols in TCP/IP Model

Static information collection and analysis refers to gathering non-changing (static) parameters of the network devices. These parameters are mostly configuration-related and do not fluctuate dynamically.

Explanation of Correct Options:

✅ A. Device types

Includes information about the hardware platform, model, and series of the device.

Example: Huawei NE40E, CE12800, or AR routers.

✅ C. License

Licenses define feature capabilities, such as MPLS, BGP, or security functions.

Licenses are static parameters because they do not change unless manually updated.

Incorrect Options:

❌ B. Interface types

Interface types (GigabitEthernet, FastEthernet, Serial, etc.) can change depending on hardware or software configurations.

They are not static because interfaces can be added or removed dynamically.

❌ D. Packet loss rate

Packet loss rate is a dynamic parameter, as it varies depending on network conditions, congestion, or faults.

It is used in performance monitoring rather than static data collection.

Reference from Huawei HCIE-Datacom Documentation:

Huawei Network Management Best Practices – Static & Dynamic Data Collection

HCIE-Datacom Guide – Network Monitoring and Analysis

Huawei NCE-Campus Network Health Check Manual

Comprehensive and Detailed Explanation:

✔ iMaster NCE-WAN provides a RESTful API for integration with third-party applications and network automation platforms.

✔ Why RESTful API?

Uses HTTP/HTTPS for communication.

Supports JSON and XML data formats.

Enables orchestration, monitoring, and automation.

✔ Why Not Other Options?❌ (A) NETCONF → Used for device-level configuration, not northbound APIs.❌ (B) SNMP → Used for network monitoring, not northbound integration.❌ (C) CLI → Used for manual command execution, not API communication.

📖 Reference: Huawei HCIE Datacom – iMaster NCE-WAN Northbound API

The Differentiated Services (DiffServ) model for Quality of Service (QoS) enables traffic management based on predefined priorities. This involves classifying, policing, queuing, and scheduling traffic to ensure efficient network resource utilization.

Breakdown of Each QoS Processing Step:

✅ Step 1: Traffic Classification and Marking

Purpose: Identifies and marks packets based on QoS attributes such as DSCP (Differentiated Services Code Point) or 802.1p priority bits.

Function: Assigns a QoS label to packets for further processing.

Example: Packets carrying voice traffic (EF - Expedited Forwarding) are marked for high-priority treatment.

✅ Step 2: Traffic Policing (CAR - Committed Access Rate)

Purpose: Enforces bandwidth limits on specific traffic flows to prevent excessive usage.

Function: Drops or re-marks packets exceeding the assigned bandwidth threshold.

Example: If a video stream exceeds 10 Mbps, excess packets may be dropped or re-marked.

✅ Step 3: Congestion Management (Queuing and Scheduling)

Purpose: Manages traffic flow through queues based on assigned QoS levels.

Function: Places packets in appropriate priority queues (e.g., Strict Priority, Weighted Fair Queuing - WFQ, CBWFQ).

Example: Voice packets are assigned to high-priority queues for low-latency forwarding.

✅ Step 4: Congestion Avoidance

Purpose: Prevents network buffer overflows and excessive packet drops.

Function: Uses mechanisms like WRED (Weighted Random Early Detection) to drop lower-priority packets before congestion occurs.

Example: If a queue reaches 80% capacity, WRED may drop low-priority packets to maintain QoS.

✅ Step 5: Traffic Shaping

Purpose: Smooths out traffic bursts to maintain a consistent transmission rate.

Function: Buffers and delays packets to prevent excessive packet drops.

Example: If outgoing traffic exceeds 50 Mbps, shaping ensures it does not exceed this limit while maintaining steady flow.

Comprehensive and Detailed Explanation:

Key Factors Affecting FTP Performance:

Tail Drop and TCP Synchronization (A) ✅

Tail Drop causes TCP global synchronization, reducing FTP speeds drastically when congestion occurs.

Since FTP is TCP-based, packet loss due to tail drop forces TCP retransmissions, further degrading performance.

Priority Preemption by Video Traffic (D) ✅

UDP-based real-time video traffic is often prioritized over TCP-based traffic to avoid jitter and packet loss.

If video traffic has higher QoS priority, FTP bandwidth may be preempted, leading to slow speeds.

Incorrect Options:

❌ Option B: PQ scheduling typically prioritizes latency-sensitive traffic (VoIP), but this scenario does not mention priority queuing for FTP.❌ Option C: No information about an explicit rate limit on FTP traffic.

📖 Reference: Huawei HCIE Datacom – QoS and Congestion Control

Understanding EVPN (Ethernet VPN) and ARP Request Handling

🔹 What is EVPN?

EVPN (Ethernet VPN) is a BGP-based control plane for VXLAN that improves Layer 2 & Layer 3 network scalability.

Eliminates flood-and-learn behavior using BGP MAC/IP advertisement routes.

🔹 Why is an ARP Request Sent?

When CE1 (192.168.1.1/24) wants to communicate with CE2 (192.168.1.2/24), it sends an ARP request to discover the MAC address of CE2.

🔹 How Does EVPN Process the ARP Request?1️⃣ PE1 receives the ARP request from CE1.2️⃣ PE1 sends a MAC/IP advertisement route (Type 2 EVPN route) to inform PE2 and PE3 of CE1’s MAC address.3️⃣ PE1 forwards the ARP request as BUM (Broadcast, Unknown unicast, and Multicast) traffic to PE2 and PE3.4️⃣ PE3 (Designated Forwarder - DF) forwards the packet to CE2.5️⃣ PE2 (Non-DF) does NOT forward the packet to avoid loops.

Analysis of the Answer Choices:

✅ A. When forwarding the packet to PE3, PE1 needs to add the BUM traffic label allocated by PE3 to the packet.

Correct:

BUM (Broadcast, Unknown Unicast, Multicast) traffic in EVPN is encapsulated with a special label assigned by the receiving PE.

PE1 adds the BUM traffic label for PE3 before sending the ARP request.

✅ B. PE1 sends a MAC/IP advertisement route carrying the MAC address of CE1.

Correct:

EVPN Type 2 MAC/IP advertisement routes are sent to inform other PEs of CE1’s MAC/IP binding.

❌ C. PE2 forwards the packet to CE1.

Incorrect:

PE2 is the Non-Designated Forwarder (Non-DF) and does NOT forward BUM traffic to avoid loops.

✅ D. PE3 forwards the packet to CE1.

Correct:

PE3 is the Designated Forwarder (DF) for this segment, meaning it forwards the ARP request to CE2.

Final Answer: A, B, D

✅ Reference: Huawei HCIE-Datacom Guide – EVPN BGP MAC/IP Advertisement and BUM Traffic Handling

Real-World Application:

Data Center Interconnect (DCI): EVPN prevents excessive ARP flooding across VXLAN networks.

Enterprise Campus Networks: Uses EVPN VXLAN to scale Layer 2 connectivity across multiple locations.

Huawei SD-WAN supports various intelligent traffic steering mechanisms to optimize link utilization and balance network traffic across multiple links.

✅ D. Traffic bandwidth-based traffic steering

This method ensures that traffic is distributed across multiple links based on available bandwidth.

SD-WAN dynamically selects links based on their real-time bandwidth utilization, ensuring optimal performance and load balancing.

For OSPF neighbors to reach Full state, they must exchange LSAs (Link State Advertisements) properly and synchronize their databases.

Possible Causes Preventing OSPF from Entering Full State:

✅ A. A link works abnormally

If the physical or Layer 2 link is unstable, OSPF Hello packets may be lost, preventing the Full state.

✅ B. The OSPF network types on both ends of the link are inconsistent

OSPF network types (Broadcast, P2P, NBMA, etc.) must match on both ends.

Example: If one router is P2P and the other is Broadcast, adjacency issues occur.

✅ C. The router IDs of neighbors are the same

Router ID conflicts prevent OSPF adjacencies from forming.

Each router must have a unique Router ID.

✅ D. The OSPF MTU values of interfaces on both ends of the link are different

If MTU settings do not match, OSPF Database Description (DD) packets may be dropped, preventing Full state.

Reference from Huawei HCIE-Datacom Documentation:

Huawei OSPF Configuration Guide – Troubleshooting OSPF Neighbor Issues

HCIE-Datacom Study Material – OSPF Adjacency and Route Synchronization