Huawei H12-831_V1.0 HCIP-Datacom-Advanced Routing & Switching Technology V1.0 Exam Practice Test

Comprehensive and Detailed In-Depth Explanation:

Understanding the BGP Network Topology in the Question:

BGP Peering & Route Distribution

Each router forms EBGP peer relationships with directly connected neighbors.

R1 and R4 import the static route 192.168.1.0/24 into BGP and advertise it to their peers.

Community attributes are attached to routes to influence routing policies.

Effect of Community Attribute 1:1

R1 marks 192.168.1.0/24 with community 1:1 before advertising it.

R3 has a policy that rejects any routes with community attribute 1:1.

Since R1’s advertisement contains 1:1, R3 will not accept 192.168.1.0/24 from R2.

Route Selection and Traffic Flow Analysis:

R1 advertises 192.168.1.0/24 with community 1:1 to R2.

R3 rejects this route from R2 because of the configured routing policy.

R4 also advertises 192.168.1.0/24 to its EBGP neighbors without community 1:1.

R5 learns the route from R4 and advertises it to R3.

Since R5’s advertisement does not include community 1:1, R3 accepts the route from R5.

Thus, the best available path for R3 to reach 192.168.1.0/24 is R3 → R5 → R1.

✅ Correct Path: R3 → R5 → R1

Checking Each Option:

❌ Option A: R3 → R2 → R4 (Incorrect)

R3 does not learn the route from R2 because it rejects community 1:1.

Since R1 added 1:1, and R2 propagated the same community, R3 will not accept this path.

❌ Option B: R3 does not have a route to 192.168.1.0/24 (Incorrect)

R3 does have a route, but it learns it from R5 instead of R2.

❌ Option C: R3 → R2 → R1 (Incorrect)

R1 marked the route with 1:1, and R2 advertised it with the same community.

Since R3 rejects 1:1 routes, it will not use this path.

✅ Option D: R3 → R5 → R1 (Correct)

R5 learns the route from R4, which does not have community 1:1, and advertises it to R3.

R3 accepts this route and forwards traffic to R5, which sends it to R1.

Final Conclusion:

✅ D. The correct path for traffic from R3 to 192.168.1.0/24 is R3 → R5 → R1.

Thus, the correct answer is: D.

Comprehensive and Detailed In-Depth Explanation:

1. Understanding MPLS TTL Processing

TTL (Time to Live) is an IP field that prevents routing loops by decrementing at each hop.

In an MPLS network, the TTL field can be processed in two modes:

Uniform Mode (Default Mode)

Pipe Mode (TTL is preserved in the MPLS domain)

2. TTL Processing in Pipe Mode

Pipe mode is used to prevent the MPLS backbone from affecting the TTL of an IP packet.

When an IP packet enters the MPLS domain, the original TTL is copied into the MPLS header.

Inside the MPLS network:

MPLS labels use their own TTL values, and the IP TTL is not decremented.

Each P router (transit router) decrements only the MPLS TTL, not the IP TTL.

When the packet leaves the MPLS domain (at PE2):

The original IP TTL is restored but decremented by 1 as it exits to CE2.

3. Analyzing the TTL Behavior in the Given Topology

Initial IP TTL from CE1 = 255

At PE1:

IP TTL remains 255 as it is copied into the MPLS label.

MPLS TTL starts at 255 (same as IP TTL).

At P Router:

MPLS TTL is decremented (255 → 254).

IP TTL remains unchanged (255) because of Pipe mode.

At PE2 (Egress Router):

IP TTL is restored and decremented by 1 (255 → 254).

Thus, the correct sequence is:✅ IP TTL: 255 → 255 → 254

4. Evaluating the Answer Choices

Option

TTL Values

Correct?

Reasoning

A

255 → 254 → 252

❌ Incorrect

IP TTL should remain 255 inside MPLS

B

254 → 253 → 252

❌ Incorrect

IP TTL starts at 255, not 254

C

255 → 255 → 254

✅ Correct

IP TTL is preserved in pipe mode inside MPLS and decremented only at egress.

D

254 → 254 → 253

❌ Incorrect

Initial IP TTL should be 255, not 254

✅ Correct Answer: C. 255 → 255 → 254

Final Conclusion:

Pipe mode ensures that the MPLS domain does not affect the IP TTL while the packet is inside the MPLS network.

Only the egress PE (PE2) decrements the IP TTL before forwarding the packet to CE2.

Thus, the correct TTL sequence is 255 → 255 → 254.

Comprehensive and Detailed In-Depth Explanation:

In IS-IS (Intermediate System to Intermediate System), each LSP (Link-State PDU) is identified by an LSP ID.

The LSP Number field is 4 bits long, meaning a single IS-IS process can generate up to 16 LSP fragments per system ID.

Since each fragment carries a limited amount of information, a router may exceed this limit if it needs to advertise a large number of routes.

Solution: By adding additional system IDs, an IS-IS router can generate more LSP fragments, thereby overcoming the limitation.

This method is commonly used in large-scale IS-IS networks to ensure scalability and efficient routing information exchange.

???? Reference: HCIP-Datacom Advanced Routing & Switching Technology – IS-IS LSP Fragmentation Mechanism

Comprehensive and Detailed In-Depth Explanation:

To verify the correct answer, let's analyze the LSA types in OSPFv3 and how they work in the given topology.

1. Understanding OSPFv3 LSAs in the Figure

From the command output shown in the image:

LS Type: Intra-Area-Prefix-LSA (Type 9 in OSPFv3).

Originating Router: 10.0.2.2 (R2).

Referenced LS Type: 0x2002, which corresponds to a Network-LSA (Type 2).

Prefix Advertised: 2000:23::/64, which is an IPv6 prefix associated with a network segment.

2. What is an Intra-Area-Prefix LSA (Type 9) in OSPFv3?

In OSPFv3, Type 9 LSAs (Intra-Area-Prefix LSAs) describe IPv6 prefixes associated with either Router-LSAs (Type 1) or Network-LSAs (Type 2).

In multi-access networks (e.g., Ethernet), the DR (Designated Router) generates a Network-LSA (Type 2), which represents the shared network segment.

R2 is likely the DR in this topology, meaning it generates a Network-LSA (Type 2) and an associated Intra-Area-Prefix LSA (Type 9) for the subnet.

3. Analyzing Why the Statement is TRUE

R2 (10.0.2.2) is the originator of the Intra-Area-Prefix LSA (Type 9).

The LSA references a Network-LSA (Type 2), confirming that R2 is the DR for the subnet.

This means the LSA is correctly describing the IPv6 prefix associated with the network.

Since the LSA is visible in R3's LSDB, R3 is learning this information from R2.

All these points confirm that the statement is TRUE.

Step 1: Understanding OSPF Areas and Summarization

Area 1 (NSSA - Not So Stubby Area)

Allows external routes but converts Type-5 LSAs into Type-7 LSAs.

External routes must be translated by an ABR into Type-5 LSAs before being propagated into other areas.

Area 2 (Common Area - Regular OSPF Area)

Supports both inter-area and external routes.

asbr-summary 10.0.4.0 255.255.255.0 Command

This command summarizes all external routes within 10.0.4.0/24 into a single summarized route.

Since it is applied on R1 and R3, these routers will advertise 10.0.4.0/24 instead of 10.0.4.4/32 to their respective areas.

Step 2: Route Distribution Analysis

R4 (Originating Router in NSSA - Area 1)

R4 injects 10.0.4.4/32 as a Type-7 LSA into Area 1.

R1 (ABR between Area 1 & Area 0, Summarizing Route)

Since R1 is an ABR, it translates Type-7 LSAs from Area 1 into a summarized Type-5 LSA (10.0.4.0/24) for Area 0.

✅ R1 has 10.0.4.0/24 in its routing table.

R2 (Inside Backbone Area 0, No ASBR Summary Applied Here)

R2 only receives Type-5 LSAs from R1 but does not summarize them.

Since R2 is not explicitly summarizing, it will likely still see 10.0.4.4/32 rather than 10.0.4.0/24.

❌ R2 does not have 10.0.4.0/24.

R3 (ABR between Area 0 & Area 2, Summarizing Route)

R3 is also an ABR and has the asbr-summary 10.0.4.0/24 command configured.

It will advertise the summarized route 10.0.4.0/24 into Area 2.

✅ R3 has 10.0.4.0/24 in its routing table.

R5 (Inside Area 2, No Direct Connectivity to External Routes)

Since R3 summarizes 10.0.4.0/24, R5 (inside Area 2) will receive only summarized routes.

✅ R5 has 10.0.4.0/24.

Final Answer: ✅ R1, R3 (Option A, C)

References:

HCIP-Datacom-Advanced Routing & Switching Technology V1.0 – OSPF Route Summarization

OSPF NSSA and Type-7 to Type-5 LSA Translation

Comprehensive and Detailed In-Depth Explanation:

Understanding the IPv6 Addressing and IS-IS Network

IPv6 Addressing in the Figure:

R1 has the address: 2000:12::1/64

R2 has the address: 2000:12::0/127

The link between them is using a /127 subnet (2000:12::0/127).

Behavior of IPv6 /127 Subnet Mask

In IPv6, a /127 prefix is commonly used on point-to-point links to avoid the issue of subnet-router anycast (::0).

RFC 6164 recommends using /127 instead of /64 for point-to-point links to reduce unnecessary anycast behavior.

2000:12::0 is the network address (first address in the subnet) and is not assigned to an interface.

Analyzing the Two Statements in the Question

Statement 1: "R1 can ping 2000:12::0" ❌ (Incorrect)

In IPv6, the first address (::0) in a /127 subnet is typically reserved as a network address and not assigned to any router.

R1 cannot ping 2000:12::0 because it is not assigned to R2 as an active IP.

Correct ping targets would be:

R1 pinging R2’s actual address (2000:12::1 or 2000:12::2 depending on numbering).

Statement 2: "display ipv6 neighbors command can be used to display the MAC address corresponding to 2000:12::0" ❌ (Incorrect)

The display ipv6 neighbors command is used to show the MAC address of an active neighbor (i.e., a reachable device).

Since 2000:12::0 is not assigned to a specific router, it will not have a MAC address in the neighbor table.

Final Conclusion:

❌ R1 cannot ping 2000:12::0 because it is the network address in a /127 subnet.❌ The display ipv6 neighbors command cannot show a MAC address for 2000:12::0 because it is not assigned to a router.

Thus, the correct answer is: B. FALSE.

A = 50

B = 10

C = 20

Comprehensive and Detailed In-Depth Explanation:

Understanding OSPF Path Selection and Cost Calculation:

OSPF selects the shortest path (lowest cost) to the destination.

The OSPF cost is determined by the cumulative sum of interface costs along a path.

By assigning specific costs to A, B, and C, we can influence OSPF’s path selection to meet the desired routing behavior.

Step-by-Step Analysis of Required Traffic Flow:

1. Traffic from PC1 to PC2 must take the route:

PC1 -> R1 -> R3 -> R2 -> PC2

To force traffic through R3, the cost of the direct link R1 -> R2 (Cost-A) must be higher than the alternative path via R3.

We assign Cost-A = 50 (high cost) to discourage direct routing from R1 -> R2.

The cost of R1 -> R3 (Cost-C) should be lower, so we assign Cost-C = 20.

The cost of R3 -> R2 (default Cost-20) remains unchanged.

Total cost via R3: 20 (R1->R3) + 20 (R3->R2) = 40, which is less than the direct link of 50, so OSPF prefers this path.

✅ Traffic follows: PC1 -> R1 -> R3 -> R2 -> PC2

2. Traffic from PC2 to PC1 must take the route:

PC2 -> R2 -> R1 -> PC1

We need to make R2 -> R1 (Cost-B) the best (lowest cost) route for return traffic.

Assign Cost-B = 10 (low cost).

This ensures that R2 prefers the direct path R2 -> R1 instead of R2 -> R3 -> R1 (which costs 20+20=40).

✅ Traffic follows: PC2 -> R2 -> R1 -> PC1

Final Cost Assignments for Correct Routing Behavior:

Cost

Assigned Value

Reason

Cost-A (R1 -> R2)

50

High to discourage direct R1->R2 routing

Cost-B (R2 -> R1)

10

Low to ensure PC2->PC1 prefers direct R2->R1

Cost-C (R1 -> R3)

20

Medium to encourage R1->R3->R2 path

Key Takeaways:

Higher OSPF cost discourages path selection.

Lower OSPF cost encourages path selection.

By manipulating OSPF cost values, we achieve asymmetric routing between PC1 and PC2.

This aligns with OSPF path selection principles covered in HCIP-Datacom certification.

HCIP-Datacom-Advanced Routing & Switching Technology References:

Huawei HCIP-Datacom Official Certification Guide, Chapter on OSPF Cost Calculation and Path Selection.

Huawei Enterprise Networking Training Materials, OSPF Path Optimization Techniques.

Huawei Datacom Configuration Guide, OSPF Cost and Traffic Engineering.

Comprehensive and Detailed In-Depth Explanation:

1. Understanding the MPLS Data Flow in the Figure

PC1 (1.1.1.1) sends a ping to PC2 (3.3.3.3).

The MPLS domain includes R1, R2, and R3.

R1 pushes an MPLS label onto the packet (Label: 300).

Packets from PC1 to PC2 are label-switched (MPLS forwarding).

Packets from PC2 to PC1 do not carry an MPLS label (IP forwarding).

2. Evaluating Each Answer Option

Option A: "If the device is R3, R3 forwards the packet from PC1 to PC2 over an IP route."

Incorrect.

The packet carries an MPLS label (Label 300) when entering the MPLS domain.

This means that R3 forwards the packet using MPLS, not a standard IP route.

If R3 were using an IP route, there would be no MPLS label in the packet.

Option B: "Packets from PC1 to PC2 are forwarded based on MPLS labels in the MPLS domain."

Correct.

The packet capture shows an MPLS label (Label 300), proving that PC1’s traffic is being forwarded using MPLS switching inside the MPLS domain.

This confirms that MPLS is being used for forwarding in one direction (PC1 → PC2).

Option C: "Packets from PC2 to PC1 are forwarded based on the IP packet header in the MPLS domain."

Correct in concept but incorrect in context.

The packet capture shows that the return traffic (PC2 → PC1) does not have an MPLS label.

However, the phrase "in the MPLS domain" makes this statement misleading, as R3 is forwarding based on pure IP routing, not MPLS forwarding.

Option D: "PC1 pings PC2."

Correct.

The packet capture clearly shows ICMP Echo Request (ping) from PC1 (1.1.1.1) to PC2 (3.3.3.3) and an ICMP Echo Reply from PC2.

This confirms that PC1 is pinging PC2 successfully.

Final Answer:

✅ B and D are correct.

HCIP-Datacom-Advanced Routing & Switching Technology References:

MPLS Label Forwarding and Static LSPs

MPLS vs. IP Routing in Different Traffic Flows

Packet Header Analysis in MPLS Networks

Comprehensive and Detailed In-Depth Explanation:

1. Understanding Site of Origin (SoO) in MPLS VPNs

SoO (Site of Origin) is used in MPLS VPNs to prevent loops in multi-homed CE scenarios.

Routes with the same SoO value are not advertised back to the same site.

2. Analysis of Each Answer Choice

A. "To enable CE3 to receive the route, run the command peer 10.1.1.1 soo 200:1 on PE1." (❌ False)

SoO is used to prevent loops by tagging routes that belong to the same site.

Applying SoO (200:1) on PE1 for CE1 means that any other PE (such as PE2) receiving the route will not advertise it back to the same site (CE1).

This statement is false because applying SoO here does not directly enable CE3 to receive the route. Instead, CE3 must accept routes with SoO values properly configured.

B. "If the commands peer 10.1.1.1 soo 200:1 and peer 10.1.2.1 soo 200:1 are run on PE1, CE2 accepts the route." (❌ False)

SoO ensures that a route received from one CE is not sent back to another CE in the same site.

If SoO (200:1) is assigned to CE1 and CE2, routes will be blocked because they share the same SoO tag.

Thus, CE2 will not accept the route, making this statement false.

C. "If the command peer 10.1.3.1 substitute-as is run on PE2, CE3 accepts the route." (✅ True)

substitute-as allows a router to replace the received AS number in the AS_PATH with another AS number, ensuring that routes are accepted even when AS_PATH filtering is in place.

This prevents CE3 from rejecting the route due to AS-Path loop prevention.

✅ Thus, this statement is true.

D. "If no additional action is taken, CE3 discards the route." (✅ True)

By default, CE3 will discard the route because of BGP loop prevention (same AS in the AS_PATH).

To allow CE3 to receive the route, the allowas-in or substitute-as command must be configured on PE2.

✅ Thus, this statement is true.

3. Evaluating the Answer Choices

Option

Correct?

Reasoning

A

❌ False

Applying SoO does not directly enable CE3 to receive the route.

B

❌ False

If both CE1 and CE2 have the same SoO value, CE2 will reject the route.

C

✅ True

Substitute-AS allows CE3 to accept the route by modifying the AS-Path.

D

✅ True

Without additional configuration, CE3 will discard the route due to AS-Path loop prevention.

✅ Correct Answer: A and B are false.

Final Conclusion:

SoO prevents routing loops in MPLS VPN multi-homing.

CE2 will reject the route if it has the same SoO as CE1.

CE3 requires the substitute-as or allowas-in command to accept the route.

Thus, statements A and B are false.

Comprehensive and Detailed In-Depth Explanation:

Understanding OSPFv3 LSA Types

OSPFv3 uses different LSA types than OSPFv2, with some being similar in function:

Link-LSA (Type 8): Generated by every router on a link to advertise link-local IPv6 information.

Intra-Area-Prefix-LSA (Type 9): Advertises IPv6 prefixes within an area.

Network-LSA (Type 2): Generated only by the Designated Router (DR) to advertise information about all routers on a multi-access network.

Inter-Area-Prefix-LSA (Type 3): Advertises network prefixes between OSPF areas (generated by ABRs).

Route Distribution Analysis:

A. Inter-Area-Prefix-LSA (Type 3) ❌ (Incorrect)

Generated by an ABR to advertise prefixes between OSPF areas.

More than one ABR can generate this LSA.

❌ Not always generated by only one router.

B. Link-LSA (Type 8) ❌ (Incorrect)

Each router generates its own Link-LSA for each link it participates in.

This means multiple routers can generate this LSA.

❌ Not generated by only one router.

C. Network-LSA (Type 2) ✅ (Correct)

Generated ONLY by the Designated Router (DR) on a multi-access network (such as an Ethernet link).

Other routers do not generate this LSA, only the DR does.

✅ Correct answer: This LSA is generated by only one router (the DR).

D. Intra-Area-Prefix-LSA (Type 9) ❌ (Incorrect)

Generated by any router to advertise IPv6 prefixes within an area.

Multiple routers in an area can generate this LSA.

❌ Not generated by only one router.

Final Conclusion:

✅ C. Network-LSA (Type 2) is the correct answer because it is generated by only one router—the Designated Router (DR).

Thus, the correct answer is: C. Network-LSA.

Comprehensive and Detailed In-Depth Explanation:

OSPFv3 (for IPv6) NSSA LSA (Type 7 LSA) is used in Not-So-Stubby Areas (NSSA).

Generated by: An ASBR (Autonomous System Boundary Router) inside the NSSA area.

Purpose: Advertises external routes (outside the AS) inside the NSSA.

Conversion: When the LSA reaches an ABR, it gets converted to a Type 5 External LSA before being propagated to other OSPF areas.

Why is this needed? NSSA areas allow some external route advertisements but do not permit normal Type 5 LSAs, so they use Type 7 LSAs instead.

???? Reference: HCIP-Datacom Advanced Routing & Switching Technology – OSPF NSSA LSA

Comprehensive and Detailed In-Depth Explanation:

Multicast MAC addresses follow the format 01-00-5E-XX-XX-XX, derived from the IPv4 multicast address (224.0.0.0 – 239.255.255.255).

The lower 23 bits of the IPv4 multicast address are mapped to the MAC address, causing ambiguity because different IPv4 multicast addresses can share the same MAC address.

The IPv4 multicast range (224.0.0.0 – 239.255.255.255) is divided as follows:✅ 224.0.0.0 – 224.0.0.255: Local Network Control Block (e.g., 224.0.0.1)✅ 224.0.1.0 – 238.255.255.255: Global and Reserved Multicast (e.g., 224.0.1.1, 225.0.1.1)❌ 239.0.0.0 – 239.255.255.255: Private Multicast (Not mapped to 01-00-5E)

The MAC 01-00-5e-00-01-01 corresponds to an IPv4 multicast address in the range 224.0.0.0 – 238.255.255.255, but not to 239.128.1.1, because addresses in the 239.x.x.x range are private multicast addresses.

???? Reference: HCIP-Datacom Advanced Routing & Switching Technology – Multicast MAC Address Mapping

Comprehensive and Detailed In-Depth Explanation:

Understanding DHCP Snooping and Trusted/Untrusted Ports

1. What is DHCP Snooping?

DHCP Snooping is a security feature that prevents rogue DHCP servers from providing unauthorized IP configurations to clients.

It categorizes switch ports into:

Trusted Ports: Allow DHCP Offer and ACK messages from a legitimate DHCP server.

Untrusted Ports: Block unauthorized DHCP responses to prevent rogue DHCP attacks.

Analyzing the Network Setup in the Figure

Interface

Connected Device

DHCP Role

Should it be Trusted?

GE0/0/1

PC1 (DHCP Client)

Requests DHCP leases

❌ Untrusted

GE0/0/2

DHCP Server (Legitimate)

Provides DHCP leases

✅ Trusted

GE0/0/3

Web Server

Not involved in DHCP

❌ Untrusted

GE0/0/4

Bogus (Rogue) DHCP Server

Malicious DHCP Server

❌ Untrusted & Blocked

GE0/0/2 is connected to the legitimate DHCP server, meaning it should be marked as a TRUSTED interface.

GE0/0/4 connects to a bogus DHCP server, which must be UNTRUSTED to block unauthorized DHCP responses.

GE0/0/1 (Client) and GE0/0/3 (Web Server) do not need to be trusted.

✅ Thus, the correct answer is: D. GE0/0/2.

Final Conclusion:

✅ GE0/0/2 should be configured as the trusted DHCP interface.❌ GE0/0/1 (Client) should remain untrusted.❌ GE0/0/3 (Web Server) does not need DHCP trust.❌ GE0/0/4 (Bogus DHCP Server) should be blocked.

Thus, the correct answer is: D. GE0/0/2.

Comprehensive and Detailed In-Depth Explanation:To determine whether the statement is true or false, we need to analyze the OSPF network, the cost values of the links, the primary and backup paths, and the role of OSPF IP Fast Reroute (FRR) enabled on R1. Let’s break it down step by step:

Understanding the Network Topology and Costs:

The network consists of four routers: R1, R2, R3, and R4.

The destination network is 10.0.3.3/32, located at R3.

The link costs are as follows:

R1 to R2: Cost = 10

R1 to R4: Cost = 10

R4 to R2: Cost = 20

R2 to R3: Cost = 5

The total cost of a path is the sum of the costs of all links in that path.

Calculating the Primary Path Cost (R1 -> R2 -> R3):

Path: R1 -> R2 (cost = 10) -> R3 (cost = 5)

Total cost = 10 + 5 = 15

This is the shortest path (lowest cost) from R1 to R3, as stated in the question. OSPF uses the Dijkstra algorithm to calculate the shortest path based on link costs, so R1 will naturally select R1 -> R2 -> R3 as the primary path to reach 10.0.3.3/32.

Calculating the Backup Path Cost (R1 -> R4 -> R2 -> R3):

Path: R1 -> R4 (cost = 10) -> R2 (cost = 20) -> R3 (cost = 5)

Total cost = 10 + 20 + 5 = 35

This path has a higher cost (35) compared to the primary path (15), which is expected for a backup path. The backup path is not used under normal conditions but is precomputed for fast failover in case the primary path fails.

Role of OSPF IP Fast Reroute (FRR):

OSPF IP FRR is a mechanism designed to provide fast convergence in case of link or node failures by precomputing backup paths. When enabled on R1, FRR ensures that R1 has a precomputed backup path to quickly switch traffic to an alternate route (e.g., R1 -> R4 -> R2 -> R3) if the primary path (R1 -> R2 -> R3) fails.

FRR typically uses Loop-Free Alternates (LFA) or other techniques to ensure the backup path does not create loops and is immediately available. In this case, the backup path R1 -> R4 -> R2 -> R3 is valid because:

It does not loop back to R1.

It reaches R3, the destination.

The cost (35) is higher than the primary path (15), but this is acceptable for a backup path.

The question states that OSPF IP FRR is enabled on R1, and the backup path is explicitly given as R1 -> R4 -> R2 -> R3. This aligns with FRR’s purpose of maintaining a precomputed backup path.

Verifying the Statement:

The statement claims: “The primary path from R1 to 10.0.3.3/32 is R1 -> R2 -> R3, and the backup path is R1 -> R4 -> R2 -> R3.”

We calculated that the primary path (R1 -> R2 -> R3) has a cost of 15, which is the shortest path and correct for OSPF’s behavior.

The backup path (R1 -> R4 -> R2 -> R3) has a cost of 35, which is higher but valid as a backup path, especially with OSPF IP FRR enabled on R1 to ensure fast failover.

Both paths are correctly identified in the question, and OSPF IP FRR’s presence on R1 supports the existence of a precomputed backup path. Therefore, the statement is accurate.

Conclusion:

The primary path (R1 -> R2 -> R3) and backup path (R1 -> R4 -> R2 -> R3) are correctly described, and OSPF IP FRR on R1 ensures the backup path is precomputed and ready for use. Thus, the statement is true.

References (Based on HCIP-Datacom-Advanced Routing & Switching Technology Concepts):

OSPF Path Calculation: HCIP-Datacom documentation on OSPF’s Dijkstra algorithm and cost-based path selection (e.g., Section on OSPF Routing Metrics).

OSPF IP Fast Reroute (FRR): HCIP-Datacom coverage of FRR mechanisms, including Loop-Free Alternates and backup path computation (e.g., Chapter on OSPF Advanced Features and High Availability).

Link Cost and Path Optimization: HCIP-Datacom explanation of link cost configuration and OSPF path selection (e.g., Section on OSPF Network Design and Optimization).

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Comprehensive and Detailed In-Depth Explanation:

To verify the correct answer, we need to analyze Bidirectional Forwarding Detection (BFD) behavior and the provided configuration.

1. Understanding BFD Configuration Parameters

BFD (Bidirectional Forwarding Detection) is a protocol used for fast failure detection between directly connected devices.

Key Configuration Parameters in BFD:

Peer IP (bind peer-ip)

This specifies the destination router’s IP address for the BFD session.

✅ Correctly configured on both R1 and R2.

Discriminator Local/Remote (discriminator local X / remote Y)

These values must match between the two routers.

✅ Correctly configured (R1: local 1, remote 2; R2: local 2, remote 1).

Min-TX Interval (min-tx-interval)

Defines the minimum transmit interval for BFD packets.

❌ Missing from R2’s configuration (could be a cause for mismatch).

Min-RX Interval (min-rx-interval)

Defines the minimum receive interval for BFD packets.

❌ Missing from R2’s configuration (could be a cause for mismatch).

2. Analyzing the Configuration on R1 and R2

✅ Configuration on R1 (Correct)

shell

CopyEdit

bfd tor2 bind peer-ip 10.0.12.2

discriminator local 1

discriminator remote 2

min-tx-interval 1500

min-rx-interval 1500

This configuration is correct.

❌ Configuration on R2 (Incomplete)

shell

CopyEdit

bfd tor1 bind peer-ip 10.0.12.1

discriminator local 2

discriminator remote 1

Missing min-tx-interval and min-rx-interval.

3. Why the Answer is FALSE?

A BFD session does NOT go down due to mismatched timing parameters.

BFD dynamically negotiates timing values, meaning even if R2 is missing min-tx/min-rx values, the session should still establish.

However, the session will fail if the peer IP or discriminator values are incorrect (which they are NOT in this case).

The actual cause of failure in this case is likely the missing min-tx and min-rx settings on R2, NOT a mismatch between R1 and R2.

Comprehensive and Detailed In-Depth Explanation:To determine whether the statement is true or false, we need to analyze the OSPFv3 topology, the role of area types, and the behavior of Inter-Area-Prefix-LSAs. Let’s break it down step by step:

Understanding the OSPFv3 Topology and Area Types:

The figure shows three routers (R1, R2, and R3) connected in an OSPFv3 network. R1 and R2 are in Area 0 (the backbone area), while R2 and R3 are in Area 1 (a common area, also known as a standard or regular area).

R2 is an Area Border Router (ABR) because it connects Area 0 and Area 1. ABRs are responsible for summarizing and advertising routes between areas.

What is a Common Area in OSPFv3?:

A "common area" in OSPFv3 refers to a standard or regular OSPF area, as opposed to special areas like Stub, Totally Stubby, Not-So-Stubby Area (NSSA), or Totally NSSA. Common areas allow all types of LSAs, including inter-area, intra-area, and external LSAs, to be flooded within the area, except for restrictions in special area types.

Since Area 1 is described as a "common area," it behaves like a standard OSPF area, allowing the full exchange of LSAs, including Inter-Area-Prefix-LSAs.

Role of Inter-Area-Prefix-LSA (Type 3 LSA in OSPFv3):

Inter-Area-Prefix-LSAs (Type 3 LSAs in OSPFv3) are used by ABRs to advertise prefixes from one area to another. These LSAs are critical for inter-area routing, allowing routers in one area to learn about networks in other areas.

In this case, R2, as an ABR, generates Inter-Area-Prefix-LSAs to describe routes (network segments) in Area 1 and advertises them into Area 0. Conversely, R2 also receives Inter-Area-Prefix-LSAs from Area 0 (via R1) and advertises them into Area 1.

Does the Inter-Area-Prefix-LSA Exist in Both Area 0 and Area 1?:

Yes, Inter-Area-Prefix-LSAs exist in both areas because R2, as an ABR, floods these LSAs into both Area 0 and Area 1. Specifically:

R2 generates Inter-Area-Prefix-LSAs for network segments in Area 1 and advertises them into Area 0, where R1 (in Area 0) can receive and process them.

Similarly, R2 receives Inter-Area-Prefix-LSAs for network segments in Area 0 (from R1) and advertises them into Area 1, where R3 (in Area 1) can receive and process them.

Since Area 1 is a common area (not a stub or NSSA), it allows Inter-Area-Prefix-LSAs to be flooded within the area, ensuring that routers like R3 can learn about routes in Area 0, and routers like R1 can learn about routes in Area 1.

Verifying the Statement:

The statement claims that R2 generates an Inter-Area-Prefix-LSA to describe the routes of a network segment in Area 1, and such an LSA exists in both Area 0 and Area 1. This is accurate because:

R2, as an ABR, generates Inter-Area-Prefix-LSAs for Area 1’s network segments and floods them into Area 0.

R2 also receives and floods Inter-Area-Prefix-LSAs from Area 0 into Area 1.

Therefore, Inter-Area-Prefix-LSAs describing routes in Area 1 exist in both Area 0 and Area 1, making the statement true.

Conclusion:

The statement is true because Inter-Area-Prefix-LSAs generated by R2 for Area 1’s network segments are flooded into both Area 0 and Area 1, and Area 1, being a common area, allows these LSAs to exist within it.

References to HCIP-Datacom-Advanced Routing & Switching Technology Documents:

HCIP-Datacom-Advanced Routing & Switching Technology V1.0, Section on OSPFv3: OSPF Area Types, Inter-Area Routing, and LSA Types (specifically Inter-Area-Prefix-LSA, Type 3 LSA).

HCIP-Datacom-Advanced Routing & Switching Technology V1.0, Chapter on OSPF Routing Protocols: ABR Behavior, Common Areas, and LSA Flooding Mechanisms.

Comprehensive and Detailed In-Depth Explanation:To determine which statement is false, we need to analyze the IS-IS topology, the role of multi-topology, the IPv6 summary configuration, and the level-1-2 behavior of IS-IS routers. Let’s break it down step by step:

Understanding the IS-IS Topology and Levels:

IS-IS supports multiple levels: Level-1 (L1) for intra-area routing, Level-2 (L2) for inter-area routing, and Level-1-2 (L1-2) routers that can operate in both levels and connect L1 and L2 areas.

In the figure, R1 and R2 are configured as Level-1-2 routers, R3 is a Level-1-2 router, R4 is a Level-1 router, and R5 is a Level-1 router. The area borders are indicated by the system IDs (49.0001 for R4’s area and 49.0002 for R3 and R5’s area).

R4’s Loopback0 has the IPv6 address 2000::/128, which is a host route (a /128 prefix, representing a single address).

Multi-Topology IS-IS for IPv6:

Multi-topology IS-IS allows separate topologies for IPv4 and IPv6, ensuring that IPv6 routes are handled independently. Since multi-topology is enabled on all routers, IPv6 routes (like 2000::/128 on R4) are advertised and processed within the IPv6 topology.

This means that IPv6 routes, including the Loopback0 address of R4 (2000::/128), can be advertised across the IS-IS domain, subject to the level and summary configurations.

IPv6 Summary Configuration (2000::/64 level-1-2):

The command ipv6 summary 2000::/64 level-1-2 is configured in the IS-IS processes of R1 and R2. This command instructs R1 and R2 (as Level-1-2 routers) to summarize the IPv6 prefix 2000::/64 and advertise it to both Level-1 and Level-2 areas.

Summarization means that instead of advertising the more specific route (e.g., 2000::/128 from R4), R1 and R2 advertise the less specific summary route 2000::/64. This summary route covers the 2000::/128 address of R4’s Loopback0.

Since R1 and R2 are Level-1-2 routers, they can advertise this summary to both their Level-1 neighbors (like R4 and R3) and Level-2 neighbors (across areas).

Analyzing Each Statement:

A. The routing table of R1 contains the route 2000::/64.

True. R1 is a Level-1-2 router with the ipv6 summary 2000::/64 level-1-2 command configured. It advertises and installs the summary route 2000::/64 in its routing table, covering the more specific 2000::/128 from R4. Additionally, as a Level-1-2 router, R1 can learn and retain this route from its IS-IS neighbors.

B. The routing table of R2 contains the route 2000::/64.

True. Similar to R1, R2 is also a Level-1-2 router with the same summary command. It advertises and installs the 2000::/64 summary route in its routing table, covering R4’s 2000::/128.

C. The routing table of R3 contains the route 2000::/128.

False. R3 is a Level-1-2 router in area 49.0002, but it receives routes from R2 (a Level-1-2 router in area 49.0001). Because R1 and R2 are configured with the ipv6 summary 2000::/64 level-1-2 command, they advertise the summary route 2000::/64 to their neighbors, including R3. IS-IS prefers the most specific route, but the summary configuration ensures that the more specific 2000::/128 from R4 is not advertised beyond R1 and R2 unless explicitly allowed. Since R3 is in a different area and receives the summary 2000::/64 from R2, it does not have the more specific 2000::/128 route in its routing table. Therefore, this statement is false.

D. The routing table of R2 contains the route 2000::/128.

True. R2, as a Level-1-2 router, is directly connected to R4 (a Level-1 router) via the IS-IS topology. R4 advertises its Loopback0 address 2000::/128 to R2. Even though R2 is configured to summarize 2000::/64, it can still retain the more specific 2000::/128 route in its routing table because IS-IS allows routers to keep both summary and more specific routes, with the more specific route taking precedence for routing decisions.

Conclusion:

The false statement is C, as R3 does not contain the route 2000::/128 in its routing table. Instead, R3 receives the summary route 2000::/64 from R2 due to the summary configuration on R1 and R2.

References to HCIP-Datacom-Advanced Routing & Switching Technology Documents:

HCIP-Datacom-Advanced Routing & Switching Technology V1.0, Section on IS-IS: Multi-Topology IS-IS for IPv6, Level-1 and Level-2 Operations, and Route Summarization.

HCIP-Datacom-Advanced Routing & Switching Technology V1.0, Chapter on IPv6 Routing Protocols: IS-IS Configuration and Behavior, Including Summary Address Commands and L1/L2 Interactions.

 Network cable → Use a tester to check connectivity.

 Device version file → Check the size of the software package and check whether the file matches the device model.

 Board → Install the board on a device that is not connected to the network and observe the running status of the device.

 License → Check whether the license is in the validity period to prevent device functions from being affected.

 Migration personnel list → Check whether responsibilities and permissions are clearly assigned.

Comprehensive and Detailed In-Depth Explanation:

1. Network Cable - Connectivity Testing:

Before starting a migration project, all network cables should be tested for physical connectivity issues.

Network testers can be used to detect any breaks, shorts, or incorrect wiring.

Ensuring proper connectivity avoids delays and troubleshooting issues during the migration.

2. Device Version File - Software Compatibility Check:

Firmware and software versions must be verified before upgrading or migrating network devices.

The device version file should match the model and hardware specifications to avoid compatibility issues.

If incorrect software is used, the device may not function properly or could become inoperable.

3. Board - Installation and Hardware Verification:

Before installing new hardware modules (boards, line cards, etc.) into a production environment, they should be tested in isolation.

Testing ensures the board is operational and does not introduce faults into the system.

If a board is faulty, it can cause device failure or unexpected behavior in the migration.

4. License - Validity and Activation Check:

Some network devices require licenses for full functionality (e.g., advanced routing, security features).

If a license is expired or missing, critical functions may be disabled after migration.

Checking license status in advance prevents unexpected downtime or service disruptions.

5. Migration Personnel List - Roles and Responsibilities Assignment:

Large network migrations require clear responsibility assignments for each team member.

A migration personnel list ensures that everyone knows their role, tasks, and permissions.

Proper coordination avoids miscommunication, errors, and project delays.

Key Takeaways:

✅ Network cables should be tested for connectivity.✅ Software versions should match the hardware model to prevent incompatibility.✅ Hardware boards should be tested before installing into production.✅ Licenses should be verified to prevent service disruptions.✅ Migration personnel roles should be clearly defined for smooth execution.

HCIP-Datacom-Advanced Routing & Switching Technology References:

Huawei HCIP-Datacom Official Certification Guide, Chapter on Network Migration Best Practices.

Huawei Enterprise Networking Whitepapers, Guidelines on Software & Hardware Pre-checks for Migration.

Huawei Technical Documentation, License Management in Huawei Datacom Devices.

Comprehensive and Detailed In-Depth Explanation:

1. Understanding MPLS LDP (Label Distribution Protocol)

LDP (Label Distribution Protocol) runs over TCP port 646.

LDP uses the transport address (Loopback0 in this case) to establish TCP sessions between neighbors.

For an LDP session to be established, both routers must:

Enable LDP on the interface (GE0/0/1).

Allow TCP traffic on port 646 (used for LDP adjacency formation).

2. Analyzing the Issue and Possible Causes

The figure shows a successful ping from R2 to R1’s Loopback0 (10.0.1.1/32).

This means basic IP connectivity between R1 and R2 is working.

OSPF is properly advertising Loopback0 addresses between the routers.

The problem must be related to LDP itself, not general IP reachability.

3. Evaluating Each Answer Option

Option A: "R1’s GE0/0/1 rejects packets with the destination IP address 10.0.2.2."

Incorrect.

The ping test in the figure shows successful replies from 10.0.1.1 to 10.0.2.2, meaning packets to 10.0.2.2 are not being rejected.

This is NOT the cause of the LDP failure.

Option B: "MPLS LDP is not enabled on R2’s GE0/0/1."

Correct.

If LDP is not enabled on R2’s GE0/0/1, then R1 and R2 cannot form an LDP session.

MPLS LDP must be enabled on both interfaces for label exchange.

This is a valid cause of the issue.

Option C: "R2’s GE0/0/1 rejects packets with TCP destination port 646."

Correct.

LDP operates over TCP port 646, so if R2’s GE0/0/1 has a firewall or ACL blocking TCP port 646, then LDP will fail.

Blocking TCP 646 on R2’s interface would prevent the session from establishing.

This is another valid cause of the issue.

Option D: "R1’s GE0/0/1 rejects packets with UDP destination port 646."

Incorrect.

LDP does not use UDP; it uses TCP port 646.

This is not a valid cause of the issue.

Final Answer:

✅ B and C are correct.

HCIP-Datacom-Advanced Routing & Switching Technology References:

MPLS LDP Session Establishment and TCP 646 Dependency

How OSPF Advertises Loopback0 for LDP Transport

Common LDP Debugging Techniques and ACL Issues

Comprehensive and Detailed In-Depth Explanation:

Understanding the network connectivity:

R1 and R2 are connected through 10.0.12.0/24 and running OSPF in Area 0.

PC1 (192.168.1.11/24) is connected to R1, and PC2 (192.168.1.12/24) is connected to R2.

Analyzing each option:

Option A: "R2 cannot ping 10.0.12.1." ❌ Incorrect

R2 is directly connected to 10.0.12.1/24 (R1) on GE0/0/0, so it can ping this IP without any routing issues.

Option B: "PC1 and PC2 cannot ping each other." ✅ Correct

OSPF is only running between R1 and R2. There is no indication that R1 and R2 are redistributing connected routes (192.168.1.0/24 and 192.168.1.0/24) into OSPF.

As a result, R1 does not know how to reach 192.168.1.12, and R2 does not know how to reach 192.168.1.11, making communication between PC1 and PC2 impossible.

Option C: "R1 cannot ping 192.168.1.2." ❌ Incorrect

192.168.1.2 is directly connected to R2, and if R1 can reach R2 through OSPF, then R1 should be able to ping 192.168.1.2.

Option D: "R1 cannot ping 192.168.1.12." ✅ Correct

192.168.1.12 is connected to R2, but if R2 does not advertise this network to R1, R1 has no route to reach it.

Since PC1 (192.168.1.11) and PC2 (192.168.1.12) are on different subnets, and there's no redistribution, R1 cannot reach PC2's IP.

Key Takeaways and Fix Recommendations:

To allow PC1 and PC2 to communicate, R1 and R2 must advertise their directly connected networks (192.168.1.0/24) in OSPF using the network command or by redistributing connected routes into OSPF.

Command example:

makefile

CopyEdit

R1:

router ospf 1

network 192.168.1.0 0.0.0.255 area 0

R2:

router ospf 1

network 192.168.1.0 0.0.0.255 area 0

This would allow R1 to learn about PC2's network and R2 to learn about PC1's network, enabling communication.

HCIP-Datacom-Advanced Routing & Switching Technology References:

HCIP-Datacom Official Certification Guide, Chapter on OSPF Network Design and Troubleshooting.

Huawei Datacom Training Materials, Section on OSPF Inter-Area and External Route Advertisements.

Huawei Datacom Configuration Guide, Command Reference for OSPF network advertisement and route redistribution.

Comprehensive and Detailed In-Depth Explanation:

OSPFv3 (for IPv6) packets are directly encapsulated in IPv6 without using UDP or TCP.

The Next Header field in IPv6 is similar to the Protocol field in IPv4, indicating the protocol type of the payload.

IANA (Internet Assigned Numbers Authority) has assigned protocol number 89 to OSPF.

OSPFv3 packets always use Next Header value = 89 inside IPv6 headers.

???? Reference: HCIP-Datacom Advanced Routing & Switching Technology – OSPFv3 Packet Encapsulation

Comprehensive and Detailed In-Depth Explanation:

Understanding the BGP and IS-IS Network Topology in the Question:

IS-IS Areas:

Area 49.0001 (Level-1 IS-IS): Contains R1, R2, R4, R5.

Area 49.0002 (Level-2 IS-IS): Contains R3, R6.

R2 acts as an ABR (Area Border Router) and redistributes routes between Level-1 and Level-2 using import-route isis level-2 into level-1.

BGP Route Reflection & Peering:

R2 and R5 are Route Reflectors (RRs).

iBGP peering is established among all routers (R1, R2, R3, R4, R5, R6).

R1 and R4 import 192.168.1.0/24 into BGP, meaning this prefix will be advertised to all iBGP peers.

R3 and R6 import 192.168.2.0/24 into BGP, meaning this prefix will also be advertised to all iBGP peers.

Route Distribution Analysis:

A. The route 192.168.2.0/24 in the routing table of R4 has two next hops. ✅ (Correct)

R3 and R6 import 192.168.2.0/24 into BGP.

R2 and R5 (Route Reflectors) learn this route and reflect it to their clients (R1, R3, R4, R6).

R4 receives two valid paths to 192.168.2.0/24 via R2 and R5 (both iBGP peers).

Since both routes have the same BGP attributes and cost, they are installed as equal-cost paths in R4's routing table.

✅ Statement A is correct: The routing table of R4 has two next hops for 192.168.2.0/24.

B. The routing table of R1 contains two equal-cost default routes. ❌ (Incorrect)

In an IS-IS Level-1-2 setup, default routes are usually provided to Level-1 routers from an ABR (like R2).

However, the question does not mention that R1 is receiving two default routes or that it is in an equal-cost multipath (ECMP) scenario.

R1 may have only one default route, depending on route preference and cost.

❌ Statement B is incorrect: The routing table of R1 does not necessarily contain two equal-cost default routes.

C. The routing table of R4 contains two equal-cost default routes. ❌ (Incorrect)

Similar to R1, R4 is also a Level-1 router in IS-IS.

If R4 were receiving default routes from multiple ABRs (R2 and R5), then it could have equal-cost paths.

However, there is no indication that R4 is receiving two default routes in this scenario.

❌ Statement C is incorrect: The routing table of R4 does not necessarily contain two equal-cost default routes.

D. The routing table of R1 contains the route 192.168.2.0/24. ✅ (Correct)

R3 and R6 import 192.168.2.0/24 into BGP.

R2 and R5 (Route Reflectors) reflect this route to their iBGP peers, including R1.

Since R1 is an iBGP client of R2 and R5, it will receive 192.168.2.0/24 and install it in its routing table.

✅ Statement D is correct: The routing table of R1 contains the route 192.168.2.0/24.

Final Conclusion:

✅ A. The route 192.168.2.0/24 in the routing table of R4 has two next hops.❌ B. The routing table of R1 does not necessarily contain two equal-cost default routes.❌ C. The routing table of R4 does not necessarily contain two equal-cost default routes.✅ D. The routing table of R1 contains the route 192.168.2.0/24.

Thus, the correct answers are: A, D.

Comprehensive and Detailed In-Depth Explanation:

Understanding the IS-IS Network and IPv6 Route Summary Behavior

IS-IS Areas and Router Roles:

Area 49.0001 (Level-1-2): R1, R2, R4

Area 49.0002 (Level-1-2 & Level-1): R3 (Level-1-2), R5 (Level-1 only)

Effect of ipv6 summary 2000::/64 level-1-2 Command on R4

Route summarization in IS-IS allows an L1-L2 router (R4) to aggregate IPv6 prefixes and advertise a summary route (2000::/64) into both Level-1 and Level-2 areas.

This means R4 will advertise only 2000::/64 instead of specific /128 routes (like 2000::4/128).

All Level-1 and Level-2 routers connected to R4 will receive the summary route 2000::/64 instead of the detailed /128 routes.

Route Distribution Analysis for Each Statement

A. The routing table of R1 contains the route 2000::4/128. ✅ (True)

R1 is a Level-1-2 router in the same area (49.0001) as R4, so it receives both the summarized 2000::/64 route and the more specific 2000::4/128 route.

Since R1 is directly connected to R4, it can still learn the 2000::4/128 route.

✅ Statement A is true.

B. The routing table of R3 contains the route 2000::/64. ✅ (True)

R3 is a Level-1-2 router, meaning it can receive both Level-1 and Level-2 routes.

Since R4 (a Level-1-2 router) advertises the summarized 2000::/64 route into both levels, R3 will receive 2000::/64 in its routing table.

✅ Statement B is true.

C. The routing table of R2 contains the route 2000::/64. ✅ (True)

R2 is a Level-1-2 router in the same area as R4, meaning it receives the summarized 2000::/64 route.

This is expected behavior since R4 advertises the summary route into both Level-1 and Level-2 areas.

✅ Statement C is true.

D. The routing table of R5 does not contain the route 2000::/64. ❌ (False - Correct Answer)

R5 is a Level-1 router, meaning it can only receive Level-1 routes unless a default route is provided.

Since R3 (a Level-1-2 router) learns 2000::/64, it can propagate it into the Level-1 area (49.0002).

This means R5 will receive the summary route 2000::/64 from R3.

Thus, R5 does contain 2000::/64, making this statement false.

❌ Statement D is false (correct answer).

Final Conclusion:

✅ A. The routing table of R1 contains the route 2000::4/128. (True)✅ B. The routing table of R3 contains the route 2000::/64. (True)✅ C. The routing table of R2 contains the route 2000::/64. (True)❌ D. The routing table of R5 does not contain the route 2000::/64. (False - Correct Answer)

Thus, the correct answer is: D. The routing table of R5 does not contain the route 2000::/64 (False Statement).

LSAs and Their Origin Router Associations:

Link-LSA: Origin Router = 10.0.1.1

Intra-Area-Prefix-LSA: Origin Router = 10.0.4.4

Network-LSA: Origin Router = 10.0.3.3

Inter-Area-Prefix-LSA: Origin Router = 10.0.1.1

Comprehensive and Detailed In-Depth Explanation:

Understanding the Table and Traffic Suppression Configuration

Port Name

Type

Rate (Min/Max)

Mode

Action

Punish-Status

Trap

Log

Int

Last-Punish-Time

GE0/0/1

Broadcast

1000 / 2000

Pps

Block

Normal

Off

On

90

-

GE0/0/1

Multicast

1000 / 2000

Pps

Block

Normal

Off

On

90

-

GE0/0/1

Unicast

1000 / 2000

Pps

Block

Normal

Off

On

90

-

Key Observations from the Table:

Traffic suppression (or rate limiting) is configured on interface GE0/0/1 for broadcast, multicast, and unicast traffic.

Thresholds:

Min rate: 1000 pps (packets per second)

Max rate: 2000 pps

If the traffic exceeds the configured threshold (2000 pps), the action is to "Block".

The interface is still "Normal" (not shut down), meaning exceeding 2000 pps does not disable the port.

Logging is enabled (Log: On), but trapping (Trap: Off) is disabled.

Analysis of Each Answer Choice

A. "When the average rate of unknown multicast packets is 1500 pps, GE0/0/1 blocks the multicast packets." ❌ (False)

The blocking threshold for multicast is 2000 pps (Max rate).

If the rate is 1500 pps, it is still below the threshold, so traffic is not blocked yet.

❌ Statement A is incorrect.

B. "When the average rate of known unicast packets is 2500 pps, GE0/0/1 is shut down." ❌ (False)

The table does not indicate that exceeding the max threshold (2000 pps) shuts down the interface.

Instead, it simply blocks packets exceeding the rate limit.

The interface remains "Normal", meaning it is not shut down.

❌ Statement B is incorrect.

C. "After broadcast packets are blocked on GE0/0/1, broadcast packets are forwarded only when their average rate is lower than 1000 pps." ❌ (False)

The minimum rate is 1000 pps, but there is no indication that traffic resumes forwarding only when it drops below this rate.

The configuration only states blocking when exceeding 2000 pps, but does not enforce a strict reactivation at 1000 pps.

❌ Statement C is incorrect.

D. "The administrator configures traffic suppression on GE0/0/1 of the switch." ✅ (True - Correct Answer)

The table explicitly shows that a traffic suppression policy is applied to broadcast, multicast, and unicast packets on GE0/0/1.

This confirms that the administrator has configured traffic suppression (rate limiting) on this interface.

✅ Statement D is correct.

Final Conclusion:

✅ Correct Answer: D. The administrator configures traffic suppression on GE0/0/1 of the switch.

Comprehensive and Detailed In-Depth Explanation:

Step 1: Understanding OSPF Areas and Summarization

Loopback0 on R5 has IP 10.0.5.5/32 and is advertised into OSPF.

The abr-summary 10.0.5.0 255.255.255.0 command is applied in area 2 on R1, which means:

Instead of advertising individual host routes (like 10.0.5.5/32), R1 advertises the summarized route 10.0.5.0/24 into Area 0 (Backbone).

This summarized route is then propagated into other areas via Area 0 (Backbone).

Step 2: Analyzing the Routing Table of Each Router

R5 (Originating Router in Area 2)

R5 only knows 10.0.5.5/32 because it's the originating router.

The abr-summary command does not affect R5 itself.

❌ R5 does not have 10.0.5.0/24.

R1 (ABR for Area 2, Summarizing the Route)

R1 creates and advertises 10.0.5.0/24 into Area 0.

This summary route is sent to other areas via Area 0.

R2 (Connected to Area 0 & Area 1)

Since R2 is part of Area 0 (Backbone), it receives 10.0.5.0/24 from R1.

✅ R2 has 10.0.5.0/24 in its routing table.

R3 (Connected to Area 0 & Area 2)

Since R3 is also connected to Area 0, it receives the summary route 10.0.5.0/24 from R1.

✅ R3 has 10.0.5.0/24 in its routing table.

R4 (In Area 1, which is not directly connected to Area 2)

R4 belongs to Area 1, and unless explicitly advertised through inter-area summarization, it will not have 10.0.5.0/24.

Since no specific mention of summary advertisement into Area 1 is made, R4 does not get 10.0.5.0/24.

❌ R4 does not have 10.0.5.0/24.

Final Answer: ✅ R2, R3 (Option B, C)

References:

HCIP-Datacom-Advanced Routing & Switching Technology V1.0 – OSPF Route Summarization

OSPF Inter-Area Route Advertisement via ABRs

OSPF Backbone (Area 0) Behavior and Route Distribution

Comprehensive and Detailed In-Depth Explanation:

Understanding the BGP Network Topology in the Question:

EBGP Peering

Each router forms EBGP peer relationships with directly connected neighbors.

This is a fully meshed topology, meaning each router exchanges BGP routes with its adjacent routers.

Routing Information for 192.168.1.0/24

R1 and R4 import the static route 192.168.1.0/24 into BGP.

Since BGP prefers the shortest AS path, traffic to 192.168.1.0/24 will follow the shortest path to R1 or R4.

Route Analysis for Each Statement:

Statement A: R6 → R5 → R4 ✅ (Correct)

R6 does not have a direct route to 192.168.1.0/24, so it must rely on BGP advertisements from its EBGP neighbors.

R5 learns the route to 192.168.1.0/24 from R4.

Therefore, R6 forwards traffic to R5, and then R5 sends it to R4.

✅ Correct path: R6 → R5 → R4

Statement B: R5 → R4 ✅ (Correct)

R5 is directly connected to R4, and since R4 advertises the 192.168.1.0/24 route via BGP,

R5 will forward traffic directly to R4 as the shortest AS path.

✅ Correct path: R5 → R4

Statement C: R2 → R1 ✅ (Correct)

R2 is directly connected to R1 and learns the 192.168.1.0/24 route from R1 via BGP.

Since R1 advertises the static route, R2 forwards traffic directly to R1.

✅ Correct path: R2 → R1

Statement D: R3 → R2 → R1 ✅ (Correct)

R3 is directly connected to R2 and learns the 192.168.1.0/24 route from R2 via BGP.

Since R2 prefers R1 as the shortest AS path to 192.168.1.0/24,

R3 will send traffic to R2, and R2 will send it to R1.

✅ Correct path: R3 → R2 → R1

Final Conclusion:

✅ A. The path for traffic from R6 to 192.168.1.0/24 is R6 → R5 → R4.✅ B. The path for traffic from R5 to 192.168.1.0/24 is R5 → R4.✅ C. The path for traffic from R2 to 192.168.1.0/24 is R2 → R1.✅ D. The path for traffic from R3 to 192.168.1.0/24 is R3 → R2 → R1.

Thus, the correct answers are: A, B, C, D.

Comprehensive and Detailed In-Depth Explanation:

The clock timezone command only affects the displayed time on the device and does not impact routing protocol operations.

Dynamic routing protocols such as OSPF, IS-IS, BGP, and EIGRP rely on timers, authentication, and correct network configurations, but they do not require the same time zone settings.

Potential issues with different time zones:✅ Log timestamps may be inconsistent, making troubleshooting harder.✅ Time-sensitive features like NTP synchronization might be affected.❌ But different time zones will not prevent dynamic routing neighbor relationships.

???? Reference: HCIP-Datacom Advanced Routing & Switching Technology – System Time Configuration & Routing Protocols

Comprehensive and Detailed In-Depth Explanation:

Understanding the BGP Network Topology in the Question:

EBGP Peering & Route Distribution

Each router forms EBGP peer relationships with directly connected neighbors.

BGP learns and propagates routes via EBGP neighbors.

R1 and R4 advertise the static route 192.168.1.0/24 into BGP.

Effect of the aggregate 192.168.1.0/16 detail-suppressed Command on R2

R2 performs BGP route aggregation, summarizing 192.168.1.0/24 into a larger 192.168.1.0/16 route.

The detail-suppressed option hides the more specific 192.168.1.0/24 prefix when advertising routes.

As a result, R2 does not advertise the specific 192.168.1.0/24 route to its neighbors.

Route Selection and Traffic Flow Analysis:

R1 and R4 originate 192.168.1.0/24 and advertise it via BGP.

R2 does not advertise the 192.168.1.0/24 route because of the detail-suppressed command.

R3 cannot learn the specific route from R2, so it must choose an alternative path via R5.

R5 learns 192.168.1.0/24 from R1 and advertises it to R3.

Thus, the best available path for R3 to reach 192.168.1.0/24 is R3 → R5 → R1.

✅ Correct Path: R3 → R5 → R1

Checking Each Option:

✅ Option A: R3 → R5 → R1 (Correct)

R3 learns 192.168.1.0/24 from R5, and R5 forwards traffic to R1, which has the static route.

❌ Option B: R3 → R2 → R1 (Incorrect)

R2 does not advertise 192.168.1.0/24 due to route summarization (detail-suppressed), so R3 cannot use R2 as the next hop.

❌ Option C: R3 → R6 → R5 → R1 (Incorrect)

This is an unnecessary detour.

R3 has a direct EBGP connection with R5, so it will use the shortest path (R3 → R5 → R1) instead of going through R6.

❌ Option D: R3 → R5 → R4 (Incorrect)

R3 prefers the shortest AS path to reach 192.168.1.0/24.

Since R1 and R4 both advertise the route, R3 will prefer the route via R5 to R1 rather than R4.

Final Conclusion:

✅ A. The correct path for traffic from R3 to 192.168.1.0/24 is R3 → R5 → R1.

Thus, the correct answer is: A.

Comprehensive and Detailed In-Depth Explanation:

1. Understanding MPLS Label Switching

MPLS (Multiprotocol Label Switching) operates by adding labels to packets to enable fast switching across an MPLS domain.

Labels are swapped at each router (LSR - Label Switch Router) based on the LFIB (Label Forwarding Information Base).

When an MPLS packet reaches a router, it checks the incoming label and swaps it with an outgoing label as per its label forwarding table.

The label value "3" is the implicit null label, which is used for PHP (Penultimate Hop Popping).

2. Analyzing the MPLS Label Flow in the Figure

At PE1: The packet enters the MPLS domain and is labeled with 1033.

At P1: P1 forwards the packet based on label 1033.

At P2:

P2 receives label 1033 and swaps it with label 3 (as per the figure).

Label 3 (implicit null) means that the label is removed before reaching PE2 (PHP - Penultimate Hop Popping).

This ensures that PE2 receives a pure IP packet without an MPLS label.

3. Evaluating Each Answer Option

Option A: "The label value is 3." → Incorrect.

Label 3 (implicit null) is not actually sent to PE2.

Instead, P2 removes the label before sending the packet to PE2.

Option B: "There is no label." → Correct.

Since P2 performs PHP (Penultimate Hop Popping), the label is removed, and PE2 receives only an IP packet.

Option C: "The label value is 1033." → Incorrect.

Label 1033 was used earlier in the MPLS path but was swapped out before reaching PE2.

Option D: "The label values are 3 and 1033." → Incorrect.

Only one label is present at a time.

Label 1033 was swapped for label 3, but label 3 was removed before reaching PE2.

Final Answer:

Answer: B (There is no label).

HCIP-Datacom-Advanced Routing & Switching Technology References:

MPLS Label Forwarding Mechanism

Penultimate Hop Popping (PHP) and Implicit Null Label (3)

MPLS Label Swapping and Label Forwarding Table (LFIB)

Comprehensive and Detailed In-Depth Explanation:

Understanding Port Isolation in the Network

Network Setup Details:

The switch is Layer 3, with VLANIF10 configured as 10.1.1.1/24 (gateway for all PCs).

All PCs are in VLAN 10 and use 10.1.1.1 as the default gateway.

Port isolation is enabled on switch interfaces, dividing them into two groups:

Group 1 (PC1 & PC2): GigabitEthernet0/0/1 and GigabitEthernet0/0/2

Group 2 (PC3 & PC4): GigabitEthernet0/0/3 and GigabitEthernet0/0/4

Port Isolation Behavior:

Ports within the same isolation group CAN communicate with each other.

Ports from different isolation groups CANNOT communicate directly.

All devices CAN still communicate with the L3 switch (10.1.1.1), which acts as the gateway.

Ping Analysis from PC1 (10.1.1.2)

Destination IP

Device

Connected Port

Isolation Group

Ping Result from PC1

10.1.1.3

PC2

GigabitEthernet0/0/2

Group 1

✅ Can Ping

10.1.1.4

PC3

GigabitEthernet0/0/3

Group 2

❌ Cannot Ping

10.1.1.5

PC4

GigabitEthernet0/0/4

Group 2

❌ Cannot Ping

10.1.1.1

L3 Switch (Gateway)

N/A

Not Isolated

✅ Can Ping

Which IPs Cannot be Pinged from PC1?

PC3 (10.1.1.4) and PC4 (10.1.1.5) are in a different isolation group (Group 2), so PC1 cannot reach them directly.

PC2 (10.1.1.3) is in the same isolation group (Group 1), so PC1 can ping it.

PC1 can ping the gateway (10.1.1.1) because the switch is Layer 3 and forwards traffic.

Thus, the correct answers are: A. 10.1.1.3 and D. 10.1.1.4.

Final Conclusion:

✅ PC1 CAN ping:

10.1.1.3 (PC2, same isolation group)

10.1.1.1 (Gateway, L3 Switch)

❌ PC1 CANNOT ping:

10.1.1.4 (PC3, different isolation group)

10.1.1.5 (PC4, different isolation group)

Thus, the correct answer is: A. 10.1.1.3 and D. 10.1.1.4.

Comprehensive and Detailed In-Depth Explanation:

This question is based on MPLS (Multiprotocol Label Switching) and its interaction with routing protocols. The goal is to ensure PC1 (10.1.1.1) can communicate with PC2 (10.3.3.1) over MPLS. Let's analyze each option carefully.

1️⃣ Understanding MPLS Routing Requirements

To forward traffic using MPLS and LDP, we need:

An IGP (Interior Gateway Protocol) like OSPF or IS-IS to advertise network reachability.

Loopback interfaces advertised in OSPF to establish LDP neighbor relationships.

Consistent MPLS LDP enablement on all links in the MPLS domain.

End-to-end IP reachability between loopbacks (since LDP uses the loopback for label distribution).

2️⃣ Option A (Correct Answer) Analysis

This configuration enables OSPF on all routers (R1, R2, and R3) across the MPLS domain:

✅ All networks are advertised in OSPF area 0, ensuring IP reachability.✅ Loopback interfaces (1.1.1.1, 2.2.2.2, 3.3.3.3) are included, which is required for MPLS LDP peer establishment.✅ PC1's network (10.1.1.0/24) and PC2's network (10.3.3.0/24) are properly advertised, ensuring end-to-end connectivity.✅ R1, R2, and R3 have OSPF neighbor relationships, meaning LDP can use OSPF routes for label switching.

???? Conclusion: Option A meets all MPLS forwarding requirements and is the correct answer.

3️⃣ Why Other Options Are Incorrect

???? Option B (Incorrect)

Uses BGP instead of OSPF, which is not optimal for MPLS forwarding in a simple MPLS domain.

LDP requires an IGP like OSPF or IS-IS to work efficiently.

BGP alone does not establish LDP label bindings between R1, R2, and R3.

???? Option C (Incorrect)

Mixes OSPF and BGP, causing routing inconsistency.

Uses ip ip-prefix and recursive lookup, which is unnecessary in a standard MPLS domain.

BGP does not distribute labels dynamically like an IGP with LDP.

???? Option D (Incorrect)

R1 does not advertise the 10.1.1.0/24 network, meaning PC1’s network is not reachable.

R3 does not advertise the 10.3.3.0/24 network, meaning PC2’s network is not reachable.

Missing essential routing entries for full end-to-end reachability.

References:

✅ HCIP-Datacom Advanced Routing & Switching Technology✅ Huawei Official MPLS and LDP Configuration Guide✅ Huawei Enterprise Networking Documentation