Huawei H12-891_V1.0 - HCIE-Datacom V1.0

InMPLS Traffic Engineering (TE),Label Switched Paths (LSPs)can be established:

Statically: Manual configuration.

Dynamically: Typically viaRSVP-TE.

Protocol roles:

RSVP-TE:Used to dynamically establish and signal TE LSPs→✅

OSPF / IS-IS: Act asIGP protocolsand provide TE-related link-state information (like bandwidth) butdo not establish LSPs themselves→❌

BGP: Used forroute advertisement, not forLSP setupin MPLS TE →❌

Correct answers: A, C, D

Comprehensive and Detailed Explanation:

Port isolationis a feature used to enhance security andnetwork segmentationby restricting communication between certain switch ports atLayer 2while allowing them to communicate throughLayer 3.

Layer 2 Communication:Devices within the same VLAN can communicate with an upstream gateway or router.

Layer 3 Isolation:Devices cannot communicatedirectlyat Layer 2 but must pass through a Layer 3 device (e.g., a router or firewall).

Use Case:Typically used in enterprise networks, hotel networks, and campus networks to preventunwanted direct communicationbetween clients.

Thus, the statement iscorrect, and the answer isTRUE.

📖Reference:Huawei HCIE Datacom Official Guide - Ethernet Port Isolation

Understanding SSH Authentication and Key Exchange

🔹What Happens When an SSH Client Connects to a Server?

1️⃣Key Exchange Phase (KEX)

Even if onlypassword authenticationis used, SSHstill performs key exchange.

The server and clientnegotiate encryption keysusing algorithms likeDiffie-Hellman (DH).

2️⃣User Authentication Phase

After encryption keys are exchanged, the userauthenticates using a username and password.

Why is the Answer FALSE?

❌Even with password authentication, SSH still performs key exchange to establish an encrypted session.

✅The SSH session is always encrypted using cryptographic keys generated during KEX.

Real-World Application:

Secure Remote Access:Protects login credentials fromMITM (Man-in-the-Middle) attacks.

Cloud & Datacenter Networks:Ensuressecure SSH connections across remote infrastructure.

✅Reference:Huawei HCIE-Datacom Guide – SSH Key Exchange and Authentication

In BGP4+ (used for IPv6 routing), the MP_REACH_NLRI attribute is used to advertise reachable routes. The Next Hop field must:

Contain a global unicast IPv6 address

Link-local addresses are not used in MP_REACH_NLRI because they are valid only on a local link and not suitable for inter-AS routing.

RFC 2545 (Multiprotocol Extensions for BGP-4) also states that the Next Hop must be a routable global address.

Therefore:

C. It must be a global unicast address — is correct.

The other options involving link-local addresses are incorrect.

Portal Authentication vs. MAC Authentication

✅Portal Authentication

Used inhigh-mobility environments(e.g., shopping malls, hotels, and public Wi-Fi hotspots).

Usersauthenticate via a web portalbefore gaining network access.

Supports multiple device types (smartphones, laptops, tablets, etc.).

✅MAC Address Authentication

Used fordumb devicesthatcannot perform interactive authentication(e.g., printers, IP phones, cameras).

The network authenticates devices based on their MAC addresses automatically.

Often used inenterprise LANsto ensureunattended devices get network access securely.

Reference from Huawei HCIE-Datacom Documentation:

Huawei CloudCampus Authentication Guide – Portal and MAC Authentication

HCIE-Datacom Training Material – Access Control Mechanisms

IGP Metric Design in Enterprise WANs

In anenterprise bearer WAN, routingmetrics determine path selection. Theaggregation layerconnects multiple access-layer devices to the core network, so it should have alower metricto:

✅Ensure traffic is forwarded through higher-capacity aggregation links instead of lower-bandwidth access links.

✅Optimize traffic flow, reduce congestion, and improve network efficiency.

✅Enhance reliability by preferring more stable aggregation links.

IGP Routing Protocols Considerations:

OSPF: Lower cost values indicate preferred paths.

IS-IS: Lower link metrics result in preferred forwarding paths.

Reference from Huawei HCIE-Datacom Documentation:

Huawei IGP Design Guide – Enterprise WAN Routing Optimization

HCIE-Datacom Training Material – Metric Calculation and Path Selection in OSPF/IS-IS

Huawei’sNQA (Network Quality Analysis)provides tools to test and monitor network performance such as latency, jitter, and packet loss. The supported test types include:

ICMP— For reachability and round-trip time testing.

UDP,TCP,HTTP,FTP, etc.

DNS,VoIP,DHCP(limited to simulation, not monitoring protocol status itself)

Protocols likeSNMPandOSPFarenot directly monitored by NQA, as these aremanagement or control plane protocols, not data-path or performance-measurable protocols.

Correct answer: C. ICMP

TheDifferentiated Services (DiffServ) modelforQuality of Service (QoS)enables traffic management based on predefined priorities. This involvesclassifying, policing, queuing, and scheduling trafficto ensure efficient network resource utilization.

Breakdown of Each QoS Processing Step:

✅Step 1: Traffic Classification and Marking

Purpose:Identifies and marks packets based onQoS attributessuch asDSCP (Differentiated Services Code Point) or 802.1p priority bits.

Function:Assigns aQoS labelto packets for further processing.

Example:Packets carryingvoice traffic (EF - Expedited Forwarding)are marked forhigh-prioritytreatment.

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

Purpose:Enforcesbandwidth limitson specific traffic flows to prevent excessive usage.

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

Example:If avideo stream exceeds 10 Mbps, excess packets may bedropped or re-marked.

✅Step 3: Congestion Management (Queuing and Scheduling)

Purpose:Managestraffic flow through queuesbased on assigned QoS levels.

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

Example:Voice packets are assigned tohigh-priority queuesforlow-latency forwarding.

✅Step 4: Congestion Avoidance

Purpose:Prevents networkbuffer overflows and excessive packet drops.

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

Example:If a queuereaches 80% capacity, WRED may droplow-priority packetsto maintain QoS.

✅Step 5: Traffic Shaping

Purpose:Smooths out traffic burststo maintain a consistenttransmission rate.

Function:Buffers and delays packetsto prevent excessive packet drops.

Example:Ifoutgoing traffic exceeds 50 Mbps, shaping ensures itdoes not exceedthis limit while maintaining steady flow.

Comprehensive and Detailed In-Depth Explanation:

TheStrict Priority (SP) scheduling algorithmalways gives preference to high-priority queues.

A:Correct. SP scheduling may lead toqueue starvationbecause low-priority queues might never get serviced if high-priority traffic is constant.

B:Correct. SP always schedules thehighest-priority queue first.

C:Correct. Among multiple low-priority queues, if SP is combined with FIFO (First In, First Out), packets that arrive first are forwarded first.

D:Incorrect. The SP algorithmdoes not guarantee minimum bandwidthfor lower-priority queues. It prioritizes high-priority queues regardless of bandwidth configuration, which can lead to starvation of lower-priority traffic. To ensure minimum bandwidth, aWeighted Fair Queuing (WFQ)orCBWFQ (Class-Based Weighted Fair Queuing)algorithm would be more suitable.

Understanding SRLB (Segment Routing Local Block)

🔹What is SRLB?

SRLB (Segment Routing Local Block)is arange of local MPLS labelsused bySegment Routing (SR-MPLS).

These labels areonly relevant to the local routerand arenot advertised to other routers.

🔹Key SR-MPLS Label Blocks:

✅SRGB (Segment Routing Global Block)– Globally significant labels shared among routers.

✅SRLB (Segment Routing Local Block)– Locally significant labels, not shared.

Why is the Answer TRUE?

✅SRLB labels are only locally defined and are NOT distributed via IGP (OSPF or IS-IS).

✅They are used for local forwarding decisions within an SR-enabled router.

✅Only SRGB labels are advertised to ensure consistent global label assignment.

Real-World Application:

Traffic Engineering (TE):Uses SRLB forcustom local path optimizations.

Segment Routing Networks:Ensuresscalable MPLS forwardingwithout requiring full LDP signaling.

✅Reference:Huawei HCIE-Datacom Guide – Segment Routing Label Blocks (SRGB & SRLB)