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

Comprehensive and Detailed In-Depth Explanation:

In SR-MPLS, if prefix SIDs conflict, the following principles are applied:

Prefix with a smaller value (numerically lower SID) wins.

If the prefix length is the same, the lower SID value is selected.

In this case:

Both 1.1.1.1/32 2 (A) and 1.1.1.1/32 1 (B) have the same prefix length.

Since SID 1 is numerically smaller than SID 2, B (1.1.1.1/32 1) is selected.

The other routes (C and D) have different prefixes and do not directly conflict.

In OSPF:

An NSSA (Not-So-Stubby Area) allows external route injection via Type 7 LSAs.

These Type 7 LSAs are generated by ASBRs inside the NSSA (R4 in this case) when external or direct routes are imported.

ABRs (such as R2) between the NSSA and backbone translate Type 7 LSAs into Type 5 LSAs for flooding into other areas.

Clarification of options:

A: Incorrect — default route is not involved here; it ' s a specific route (10.1.4.4/32).

B: Correct — R2 translates Type 7 LSAs into Type 5.

C: Incorrect — default route is not being advertised.

D: Correct — R4 imports a direct route and generates Type 7 LSAs for it.

Correct answers: B, D

Comprehensive and Detailed Explanation:

VGMP (Virtual Group Management Protocol) is used in Huawei firewalls for hot standby and high availability.

When is VGMP Activated?✔ When hot standby is enabled, firewalls must synchronize their states to maintain failover capability. ✅✔ VGMP sends packets periodically to check if the standby firewall is operational.

Why Other Options Are Incorrect?❌ Priority increase (B): Does not trigger VGMP packets directly.❌ Link detection timeout (C): Affects failover but does not initiate VGMP packets.❌ Hot standby being disabled (A): Disables VGMP, preventing packets from being sent.

Thus, the correct answer is D.

???? Reference: Huawei HCIE Datacom – Firewall Hot Standby and VGMP

Understanding BGP Link State (BGP-LS)

???? What is BGP-LS?

BGP-LS (BGP Link-State) is an extension of BGP that allows routers to exchange network topology information via Link-State NLRI.

Helps SDN controllers and path computation elements (PCEs) make intelligent routing decisions.

???? What Does BGP-LS Advertise?

✅ Node Information – Router IDs, Loopbacks

✅ Link Information – Bandwidth, Delay, Cost

✅ Prefix Information – Network Subnets

✅ Topology Information – Full network graph

Why is the Answer TRUE?

✅ BGP-LS introduces a new NLRI format for advertising link-state information.

✅ NLRI (Network Layer Reachability Information) is used to distribute topology data to SDN controllers.

✅ It improves path optimization by enabling centralized traffic engineering decisions.

Real-World Application:

SDN-Based Traffic Engineering: Used in Segment Routing (SR) networks for centralized path selection.

MPLS TE (Traffic Engineering): Optimizes network paths dynamically based on real-time link-state data.

✅ Reference: Huawei HCIE-Datacom Guide – BGP Link-State (BGP-LS) Fundamentals

To determine R3’s role (Level-1, Level-2, or Level-1-2) based on the provided output of the display ipv6 routing-table protocol isis command on R3, we need to analyze the IS-IS routing information and understand IS-IS hierarchy and behavior, particularly in the context of IPv6 routing. Let’s break it down step by step:

Understanding the IS-IS Levels and Hierarchy:

IS-IS (Intermediate System to Intermediate System) is a link-state routing protocol that supports a two-level hierarchy:

Level-1: Routers within the same area, responsible for intra-area routing. Level-1 routers only maintain routing information for their area and rely on Level-1-2 routers to reach other areas.

Level-2: Routers that form the backbone, connecting different areas for inter-area routing. Level-2 routers maintain routing information across areas.

Level-1-2: Routers that operate both at Level-1 (within their area) and Level-2 (to connect to other areas). These routers act as boundary routers between Level-1 areas and the Level-2 backbone.

A router’s role (Level-1, Level-2, or Level-1-2) determines which types of adjacencies it can form and what routing information it advertises or receives.

Analyzing the Output:

The output shows R3’s IPv6 routing table with routes learned via IS-IS, specifically:

Destination: 2082:EDFC:DDCC::B824:0/127, Protocol: ISIS-L1

This route is learned via IS-IS Level-1 (ISIS-L1), indicating that R3 has a Level-1 adjacency and is receiving or advertising routes within its area.

The next hop (FE80::2E0:FCFF:FE45:6A3E) and interface (GigabitEthernet0/0/0) suggest this route is intra-area.

Destination: 2082:EDFC:DDCC::B891:0/127, Protocol: ISIS-L2

This route is learned via IS-IS Level-2 (ISIS-L2), indicating that R3 has a Level-2 adjacency and is receiving or advertising routes for inter-area or backbone routing.

The next hop (FE80::2E0:FCFF:FE50:406F) and interface (GigabitEthernet0/0/1) suggest this route is for a different area or the backbone.

Both Level-1 and Level-2 routes are present in R3’s routing table, which provides critical insight into R3’s role.

Determining R3’s Role:

Level-1 Routers:

Level-1 routers only participate in Level-1 adjacencies and maintain routing information for their area. They do not have Level-2 routes or adjacencies unless connected to a Level-1-2 router. Since R3 has a Level-2 route (ISIS-L2), it cannot be exclusively a Level-1 router.

Level-2 Routers:

Level-2 routers focus on inter-area routing and typically do not maintain Level-1 routes unless they are also configured as Level-1-2. Since R3 has a Level-1 route (ISIS-L1), it cannot be exclusively a Level-2 router.

Level-1-2 Routers:

Level-1-2 routers operate both at Level-1 (for intra-area routing) and Level-2 (for inter-area routing). They can form adjacencies with both Level-1 and Level-2 neighbors and maintain both types of routes. The presence of both ISIS-L1 and ISIS-L2 routes in R3’s routing table indicates that R3 is participating in both Level-1 and Level-2 adjacencies, making it a Level-1-2 router.

Evaluating Each Option:

A. R3 must be a Level-2 device.

This is incorrect because R3 has ISIS-L1 routes, indicating it is also participating in Level-1 adjacencies, which Level-2-only devices do not do. Level-2 devices focus solely on inter-area routing and do not maintain Level-1 routes.

B. The device role of R3 cannot be determined.

This is incorrect because the presence of both ISIS-L1 and ISIS-L2 routes in the routing table clearly indicates R3’s role. The combination of Level-1 and Level-2 routes confirms R3 is a Level-1-2 router.

C. R3 must be a Level-1-2 device.

This is correct. The routing table shows both ISIS-L1 (Level-1) and ISIS-L2 (Level-2) routes, meaning R3 is operating as both a Level-1 and Level-2 router, which defines a Level-1-2 device.

D. R3 must be a Level-1 device.

This is incorrect because R3 has ISIS-L2 routes, indicating it is also participating in Level-2 adjacencies, which Level-1-only devices do not do. Level-1 devices only maintain intra-area routes and rely on Level-1-2 routers for inter-area reachability.

Additional Considerations:

The Flags: D in the output typically indicates a directly connected route or a route downloaded to the forwarding table, but it does not affect the determination of R3’s IS-IS level.

The preference (15) and cost (20) are standard for IS-IS routes and do not impact the level determination.

In Huawei’s IS-IS implementation, routers can be configured explicitly as Level-1, Level-2, or Level-1-2 using commands like isis level-1-2 under the IS-IS process. The presence of both Level-1 and Level-2 routes confirms R3’s configuration as Level-1-2.

Huawei HCIE-Datacom Context:

According to Huawei HCIE-Datacom documentation, IS-IS routers can operate at different levels, and the routing table’s protocol type (ISIS-L1 or ISIS-L2) indicates the level of adjacency. A router with both Level-1 and Level-2 routes is necessarily a Level-1-2 device, as it participates in both intra-area and inter-area routing.

The display ipv6 routing-table protocol isis command on Huawei devices shows routes learned via IS-IS, and the protocol type (L1 or L2) directly reflects the router’s role in the IS-IS hierarchy.

Conclusion:

Based on the presence of both ISIS-L1 and ISIS-L2 routes in R3’s IPv6 routing table, R3 must be a Level-1-2 device, as it is participating in both Level-1 (intra-area) and Level-2 (inter-area) adjacencies. Therefore, the correct answer is C.

References to Huawei HCIE-Datacom Documents:

Huawei HCIE-Datacom V1.0 Training Material, Chapter on IS-IS Configuration and Hierarchy.

Huawei NE Series Router Configuration Guide, IS-IS Section (Level-1, Level-2, and Level-1-2 Operations).

Huawei Technical Whitepaper on IS-IS Protocol, discussing IPv6 Routing and Level Determination.

Comprehensive and Detailed Explanation:

✔ Analyzing the Python Code:

✅ (A) Correct → print(r.json()) prints the response JSON, showing the token ID.

✅ (B) Correct → The token request URL is correctly specified.

✅ (D) Correct → json={ " userName " : nbi_name, " password " : nbi_pwd} confirms the request body is in JSON format.

❌ (C) Incorrect:

The request uses POST, not GET (requests.post() is explicitly called).

???? Reference: Huawei HCIE Datacom – RESTful API Authentication in iMaster NCE

Comprehensive and Detailed Explanation:

✔ SR-MPLS Policy candidate paths are used for flexible path selection and load balancing in Segment Routing (SR-MPLS) networks.

✔ Correct Statements:

✅ (A) Each candidate path can have multiple segment lists, each with its own weight for load balancing.

✅ (B) Load balancing is supported both between candidate paths and within segment lists.

✅ (C) An SR-MPLS Policy can contain multiple candidate paths, each with a preference value.

✅ (D) The candidate path with the highest preference is selected as the primary path.

???? Reference: Huawei HCIE Datacom – SR-MPLS Policy Path Selection

Comprehensive and Detailed Explanation:

IP Source Guard (IPSG) is a Layer 3 security feature used to protect against IP address spoofing by filtering packets based on bound IP-MAC mappings.

Correct Statements:✔ IPSG is a Layer 3 filtering mechanism that checks if the source IP address of a packet matches the learned or configured bindings (Option B).✔ IPSG prevents unauthorized IP address changes by enforcing binding rules (Option C).✔ IPSG defends against IP spoofing attacks by dropping packets from unauthorized sources (Option D).

Incorrect Statement:❌ Option A is incorrect because IPSG does not send alarms to an NMS when an invalid packet is detected. Instead, it drops the packet.

Thus, the correct answer is A.

???? Reference: Huawei HCIE Datacom Security Guide - IP Source Guard (IPSG)

Comprehensive and Detailed Explanation:

✔ MPLS labels in SR-MPLS are calculated using the SRGB (Segment Routing Global Block) base and the Prefix-SID.

✔ Label Calculation Formula:

MPLS Label=SRGB Base+Prefix-SID\text{MPLS Label} = \text{SRGB Base} + \text{Prefix-SID}MPLS Label=SRGB Base+Prefix-SID

✔ Extracting Values from the LSDB:

SRGB Base: 36000

Prefix-SID: 300

✔ Valid MPLS Labels:

36000 + 300 = 36300

40002 and 38002 fall within the SRGB range.

39002 is outside the expected range, making it the incorrect answer.

???? Reference: Huawei HCIE Datacom – Segment Routing Label Calculation

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