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

Comprehensive and Detailed In-Depth Explanation:

Understanding the DHCP Process in This Scenario:

DHCP Server on R2:

The DHCP server is configured on interface GE0/0/0 of R2.

The address pool is an interface address pool, meaning that IP addresses are allocated from the subnet of GE0/0/0 (i.e., 10.0.12.0/24).

DHCP Clients on R1:

Both interfaces (GE0/0/0 and GE0/0/1) on R1 are set as DHCP clients, meaning they will send DHCP DISCOVER messages to obtain an IP address dynamically.

Why Only One Interface Gets an IP Address?

Interface address pools in Huawei devices assign only one IP address per MAC address (which is typically the router’s MAC).

Since both interfaces belong to R1, they share the same MAC address when making a DHCP request.

As a result, the DHCP server on R2 only assigns one IP address to the first requesting interface.

The second request is ignored or denied by the DHCP server due to the duplicate MAC address issue.

Key Takeaways:

Huawei routers using an interface-based DHCP address pool assign only one IP per MAC address.

Since both interfaces on R1 have the same MAC, only one gets an IP.

This behavior is expected in Huawei’s HCIP-Datacom-certified DHCP configurations.

HCIP-Datacom-Advanced Routing & Switching Technology References:

Huawei HCIP-Datacom Official Certification Guide, Chapter on DHCP Server and Client Configurations.

Huawei Datacom Configuration Guide, Section on Interface Address Pools and Address Assignment Limitations.

Huawei Enterprise Networking Training Materials, DHCP Relay and DHCP Server Behavior.

Comprehensive and Detailed In-Depth Explanation:

To determine which statements are false, we need to understand how OSPFv3 and IS-IS work together, and how Inter-Area-Router LSAs (Type 3 LSAs) are generated in OSPF:

1. Understanding OSPF Inter-Area LSAs (Type 3)

OSPF generates Type 3 LSAs (Inter-Area-Prefix LSAs) to advertise networks between areas.

Only Area Border Routers (ABRs) generate Inter-Area LSAs.

Type 3 LSAs allow routes to be advertised from one OSPF area to another (e.g., from Area 0 to Area 1 or Area 2).

2. Analysis of Each Answer Option:

✅ A. "R3 generates an Inter-Area-Router-LSA in Area 0." → TRUE

R3 is an ABR (connecting IS-IS and OSPF Area 0).

Since R3 is importing IS-IS routes into OSPFv3, it must generate Type 3 LSAs to advertise those routes in Area 0.

This statement is correct.

✅ B. "R2 generates an Inter-Area-Router-LSA in Area 0." → TRUE

R2 is also an ABR (connecting IS-IS and OSPF Area 0).

Like R3, R2 imports IS-IS routes into OSPFv3 and advertises them into Area 0 using Type 3 LSAs.

This statement is correct.

❌ C. "R1 generates an Inter-Area-Router-LSA in Area 2." → FALSE

R1 is not an ABR.

Only ABRs generate Type 3 LSAs, and R1 is not an ABR between Area 2 and Area 0.

This statement is false.

❌ D. "R2 generates an Inter-Area-Router-LSA in Area 1." → FALSE

Area 1 is a stub area, and stub areas do not allow Inter-Area-Router LSAs (Type 3 LSAs) for external routes.

R2 does not generate Inter-Area LSAs in Area 1 because OSPF prevents this in stub areas.

This statement is false.

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:

To determine the correct answer, we need to analyze how each command impacts OSPF neighbor relationships.

1. Understanding OSPF Neighbor Formation

OSPF routers form neighbor relationships when they meet the following conditions:

They are in the same subnet (IP addresses and subnet masks must match).

They are in the same OSPF area.

They use the same network type (e.g., Broadcast, Point-to-Point).

Authentication (if configured) must match.

Hello and Dead timers must match.

2. Analyzing Each Answer Option

❌ A. "undo ip address 10.0.12.2 24" → Affects OSPF Neighbor Status

Removing the IP address will prevent the interface from sending and receiving OSPF Hello packets.

Without an IP address, OSPF cannot establish neighbor relationships.

Effect: Breaks OSPF neighbor status.

✅ B. "undo description" → Does NOT Affect OSPF Neighbor Status

The interface description is just a label for administrators and has no impact on OSPF functionality.

It does not affect neighbor relationships, routing, or communication.

Effect: No impact on OSPF neighbors.

❌ C. "undo ospf cost" → Affects OSPF Neighbor Status Indirectly

OSPF cost determines the path selection but does NOT break the neighbor relationship.

However, if the cost change leads to routing table recalculations, it might cause temporary convergence issues.

Effect: Does not directly break neighbor status, but affects route selection.

❌ D. "undo ospf dr-priority" → Affects OSPF Neighbor Status (Possibly Causes DR Re-Election)

OSPF DR/BDR election uses priority values.

If changed, a new election might occur, leading to a temporary loss of neighbor relationships.

Effect: Might cause OSPF neighbor reset (temporary impact on adjacency).

Comprehensive and Detailed In-Depth Explanation:

1. Understanding MPLS Label Forwarding Information

The output of the display mpls lsp command shows the Label Forwarding Information Base (LFIB) used by the router to forward MPLS packets.

Each entry consists of:

FEC (Forwarding Equivalence Class): The destination IP prefix.

In Label / Out Label: Incoming label (received) and outgoing label (sent).

In IF / Out IF: Incoming and outgoing interfaces.

2. Analyzing the Given LSP Table

FEC (Destination IP)

In Label

Out Label

Outgoing Interface

1.1.1.1/32

3

NULL

-

2.2.2.2/32

NULL

3

GE0/0/1

2.2.2.2/32

1026

3

GE0/0/1

3.3.3.3/32

NULL

1027

GE0/0/1

3.3.3.3/32

1027

1027

GE0/0/1

Key Observations:

NULL means the label is removed (Penultimate Hop Popping - PHP).

Label 3 is the implicit null label, meaning the label is removed before sending to the next router.

For destination 3.3.3.3, the router adds label 1027 before forwarding it to GE0/0/1.

3. Evaluating Each Answer Option

Option A: "Before forwarding a packet destined for 2.2.2.2, the device adds label 3 to the packet." → Incorrect.

The output shows that packets destined for 2.2.2.2 have the NULL (label 3) entry, which means the label is removed before forwarding, not added.

Option B: "Before forwarding a packet destined for 1.1.1.1, the device adds label 3 to the packet." → Incorrect.

The entry 1.1.1.1 → 3/NULL means the label is removed (PHP), so the device does not add label 3.

Option C: "Before forwarding a packet destined for any IP address, the device removes labels from the packet." → Incorrect.

The device removes labels only for some destinations (e.g., 1.1.1.1 and 2.2.2.2), but it adds label 1027 for 3.3.3.3.

Not all IPs have their labels removed.

Option D: "Before forwarding a packet destined for 3.3.3.3, the device adds label 1027 to the packet." → Correct.

The entry 3.3.3.3 → NULL/1027 means that the router adds label 1027 before forwarding packets to GE0/0/1.

Final Answer:

Answer: D (Before forwarding a packet destined for 3.3.3.3, the device adds label 1027 to the packet).

HCIP-Datacom-Advanced Routing & Switching Technology References:

Understanding MPLS LDP (Label Distribution Protocol) and LFIB

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

MPLS Label Swapping and Forwarding Process

Comprehensive and Detailed In-Depth Explanation:

1. Understanding VPN Route Targets (RTs) in MPLS VPNs

Route Targets (RTs) define which VPN routes should be imported and exported among PE routers.

Import-extcommunity: Specifies which VPN routes should be accepted into a VRF.

Export-extcommunity: Specifies which VPN routes should be advertised from a VRF.

Correctly configuring RTs ensures proper route exchange between VPN sites.

2. Analyzing the RTs in the Diagram

R3's Current Configuration:

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vpn-target 3:1 export-extcommunity

vpn-target 3:2 export-extcommunity

vpn-target 1:3 export-extcommunity

vpn-target 1:3 import-extcommunity

vpn-target 3:1 import-extcommunity

vpn-target 3:2 import-extcommunity

R1's Configuration:

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vpn-target 1:3 export-extcommunity

vpn-target 3:1 import-extcommunity

R2's Configuration:

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vpn-target 2:3 export-extcommunity

vpn-target 3:2 import-extcommunity

R3 has redundant RTs because it both exports and imports unnecessary RTs.

We need to remove only redundant RTs without affecting NMS connectivity.

3. Evaluating Each Answer Choice

A. "undo vpn-target 3:1 import-extcommunity" (❌ Incorrect)

R1 exports RT 1:3, and R3 imports it as 3:1.

Removing 3:1 import-extcommunity would block R3 from receiving routes from R1, disrupting connectivity to NMS.

Thus, this option is incorrect.

B. "undo vpn-target 1:3 export-extcommunity" (✅ Correct)

R3 exports RT 1:3, but there is no need for R3 to advertise routes with 1:3.

R1 already exports 1:3, and R3 only needs to import it.

Removing vpn-target 1:3 export-extcommunity does not affect connectivity but eliminates redundancy.

✅ This is a correct choice.

C. "undo vpn-target 1:3 import-extcommunity" (❌ Incorrect)

R3 needs to import 1:3 to receive routes from R1 (which is required for NMS communication).

If removed, R3 will not receive necessary routes, breaking connectivity.

Thus, this option is incorrect.

D. "undo vpn-target 2:3 export-extcommunity" (✅ Correct)

R2 exports RT 2:3, but R3 does not need to receive it.

This RT is redundant and can be removed without affecting connectivity.

✅ This is a correct choice.

4. Evaluating the Answer Choices

Option

Correct?

Reasoning

A

❌ Incorrect

R3 must import 3:1 from R1 to maintain connectivity.

B

✅ Correct

Removing export-extcommunity 1:3 eliminates redundancy without affecting connectivity.

C

❌ Incorrect

Removing import-extcommunity 1:3 would block R3 from receiving necessary routes.

D

✅ Correct

Removing export-extcommunity 2:3 eliminates redundancy without affecting connectivity.

✅ Correct Answer: B and D.

Final Conclusion:

Route Targets (RTs) are used in MPLS VPNs to control route import/export policies.

R3 has redundant RTs, and removing unnecessary exports (1:3 and 2:3) optimizes configuration.

Correct commands to remove redundancy without affecting connectivity are:

✅ undo vpn-target 1:3 export-extcommunity

✅ undo vpn-target 2:3 export-extcommunity

Thus, the correct answer is: B and D.

Comprehensive and Detailed In-Depth Explanation:

The display startup command is used to check the startup and running configuration details of a Huawei network device.

It provides information on:✅ Running system software (currently active firmware).✅ Running configuration file (current settings in use).✅ Startup system software (firmware that will load on reboot).✅ Startup configuration file (configuration that will be applied on reboot).✅ Paths of these files in the storage system.

This command helps network administrators ensure that the correct firmware and configuration files are used when the device boots.

📖 Reference: HCIP-Datacom Advanced Routing & Switching Technology – System Management and Configuration Files

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.