H12-891_V1.0 Exam Dumps - Huawei HCIE-Datacom Questions and Answers

Understanding Inter-AS MPLS L3VPN Option C

???? MPLS L3VPN provides Layer 3 VPN services over an MPLS backbone by using BGP to exchange VPN routes.

???? Inter-AS MPLS L3VPN Option C (Carrier-to-Carrier Model) works as follows:

ASBRs (Autonomous System Boundary Routers) exchange VPNv4 routes using MP-BGP.

ASBRs do NOT store VPN routing tables. Instead, they advertise labeled IPv4 routes to enable inter-AS forwarding.

How ASBR-PE2 Enables Inter-AS Communication?

✅ VPNv4 Address Family (Answer A - Required)

Used to exchange MPLS VPN routes between PE routers.

MP-BGP (Multiprotocol BGP) exchanges VPNv4 prefixes between ASBR-PE1 and ASBR-PE2.

✅ Unicast BGP Address Family (Answer D - Required)

Required to exchange IPv4 labeled routes between ASBRs.

Ensures MPLS label forwarding between AS100 and AS200.

❌ BGP-LS Address Family (Answer B - Not Required)

BGP-LS (BGP Link-State) is used for SDN controllers to learn topology information.

It is not required for Inter-AS MPLS L3VPN.

❌ VPN Instance Unicast Address Family (Answer C - Not Required)

This is used for PE-CE communication but is not required between ASBRs.

Why is the Answer A, D?

✅ VPNv4 routes enable inter-AS VPN communication.

✅ IPv4 unicast routes are required for ASBR-PE2 to forward packets across AS boundaries.

Real-World Application:

Service Provider Networks: Used in carrier-to-carrier MPLS VPN deployments.

Enterprise WAN Interconnection: Enables multi-AS MPLS VPN connectivity for large enterprises.

✅ Reference: Huawei HCIE-Datacom Guide – Inter-AS MPLS L3VPN Option C (Carrier-to-Carrier Model)

Understanding VXLAN (Virtual eXtensible LAN) Technology

VXLAN is a Layer 2 over Layer 3 encapsulation protocol designed to extend Layer 2 domains across routed networks using MAC-in-UDP encapsulation.

???? Key VXLAN Components:

VTEP (VXLAN Tunnel Endpoints): These encapsulate and decapsulate VXLAN packets.

Underlay Network: The routed IP network that forwards VXLAN packets (does not require VXLAN awareness).

Overlay Network: The logical Layer 2 segments tunneled over VXLAN.

Analysis of the Answer Choices:

✅ A. VXLAN uses MAC-in-UDP encapsulation to encapsulate Ethernet packets into UDP packets and thereby extend Layer 2 networks.

Correct: VXLAN uses MAC-in-UDP encapsulation, meaning that the original Ethernet frame is placed inside a UDP packet, allowing Layer 2 networks to extend over IP-based networks.

❌ B. When VXLAN is deployed, in addition to devices at both ends of a VXLAN tunnel, intermediate forwarding devices are also required to support VXLAN. Otherwise, VXLAN packets cannot be forwarded.

Incorrect: VXLAN packets are forwarded as regular UDP traffic in the underlay network.

Intermediate routers or switches DO NOT need to support VXLAN, as they only forward UDP packets based on the outer IP headers.

Only VTEP devices must support VXLAN because they handle encapsulation/decapsulation.

✅ C. VXLAN packets are forwarded through routes on the underlay network, and the MAC address of the terminal in the inner data frame is not considered during underlay forwarding.

Correct: The underlay network routes VXLAN packets using outer IP headers (VTEP IP addresses), not the inner MAC address.

✅ D. VXLAN can be deployed on campus networks to implement Layer 2 and Layer 3 communication.

Correct: VXLAN is commonly used in campus networks to provide both Layer 2 bridging and Layer 3 routing across different locations.

Real-World Application:

Data Center Networks: VXLAN is widely used for multi-tenant network segmentation in cloud environments.

Enterprise Campus Networks: Enables seamless Layer 2 and Layer 3 connectivity across different buildings or locations.

✅ Reference: Huawei HCIE-Datacom Guide – VXLAN Deployment and Forwarding Principles

This statement confuses congestion management with congestion avoidance:

Congestion Management: Refers to techniques like PQ, CQ, WRR, etc., to schedule packets in queues — i.e., manage how packets are sent, not discarded.

Congestion Avoidance: Techniques like WRED are used to preemptively discard packets to avoid full queues — these do discard packets.

Hence, congestion management does NOT discard packets — it ' s about controlling transmission order and prioritization.

Correct answer: B. FALSE

Comprehensive and Detailed In-Depth Explanation:

In BGP EVPN, Type 2 routes (MAC/IP Advertisement routes) are used to advertise:

MAC addresses of endpoints.

ARP entries (MAC-to-IP bindings).

IRB (Integrated Routing and Bridging) routes, allowing the advertisement of both Layer 2 and Layer 3 reachability.

These routes are essential for enabling dynamic VXLAN tunnel establishment and seamless host mobility.

Type 1 (Ethernet Auto-Discovery): Used for multi-homing information.

Type 3 (Inclusive Multicast Ethernet Tag): Used for BUM (Broadcast, Unknown unicast, and Multicast) traffic.

Type 4 (Ethernet Segment): Used for identifying Ethernet segments in multi-homing scenarios.

Before performing a network cutover (migration or upgrade), it is essential to collect baseline data to ensure that services operate normally before and after the change.

Importance of Pre-Cutover Information Collection:

Identifies Network Baseline – Helps compare pre-cutover and post-cutover performance.

Detects Hidden Issues – Ensures that no existing network issues interfere with the cutover process.

Prevents Service Interruptions – Ensures all dependent services are accounted for.

Provides Rollback Plan – If issues arise, administrators can restore previous configurations.

Reference from Huawei HCIE-Datacom Documentation:

Huawei Network Change Management Guide – Pre-Cutover & Post-Cutover Best Practices

HCIE-Datacom Training Material – Service Assurance & Risk Analysis

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)

Link-LSA (Type 8) in OSPFv3 performs the following:

Advertises the router’s link-local address to neighbors.

Advertises the router’s interface ID on the link.

Carries IPv6 prefixes associated with the interface (since Router LSA no longer does this in OSPFv3).

The Options field in Link-LSA contains capabilities of the originating router, not the options from Network-LSA.

So, Option D is incorrect — the Link-LSA does not advertise options from the Network-LSA.

Correct answer: D

IS-IS was originally designed for IPv4, but extensions via TLVs (Type-Length-Value) allow it to support IPv6. These are referred to as New IS-IS TLVs, including TLV 236 (IPv6 Reachability), TLV 232 (IPv6 Interface Address), etc. These TLVs are crucial for IPv6 route computation within IS-IS.

Exact Extract - HCIE-Datacom Guide – IPv6 Routing Protocols Chapter

“IS-IS uses new TLVs such as TLV 236 and TLV 232 to carry IPv6 prefix and interface address information. These TLVs are essential to enable IPv6 route calculation.”

In OSPFv3, each LSA type has a defined flooding scope:

Link-LSA (Type 8)

Advertised only on the local link

Contains router’s link-local address and prefixes

Scope: Within the local link scope ✅

AS-External-LSA (Type 5)

Used to advertise external routes from outside the AS

Flooded across the entire autonomous system, except stub/NSSA areas

Scope: Within an AS ✅

Network-LSA (Type 2)

Generated by the Designated Router (DR)

Describes all routers on a broadcast or NBMA segment

Flooded within the originating area

Scope: Within an area ✅

Correct Mappings:

Link LSA → Within the local link scope

AS-External-LSA → Within an AS

Network-LSA → Within an area

The basic constructs in YANG data modeling include:

Leaf node – A single data element with a specific type (e.g., integer, string).

List node – A repeating set of elements, each structured the same.

Incorrect options:

A. Set node – ❌ Not a valid YANG construct.

D. Tree node – ❌ Not an individual data model element. The entire model forms a tree structure, but there is no “tree node” in YANG syntax.

Exact Extract – Huawei YANG Modeling Fundamentals:

“YANG defines elements such as leaf, list, container, choice, and leaf-list. ' Set ' and ' tree ' are not YANG node types.”