H12-831_V1.0 Huawei HCIP-Datacom-Advanced Routing & Switching Technology V1.0 Free Practice Exam Questions (2025 Updated)

Comprehensive and Detailed In-Depth Explanation:

To determine which routers are unable to import external routes, we need to analyze the behavior of each OSPF area type:

Stub Area (Area 1 - Contains R6)

Stub areas do not allow external routes (Type-5 LSAs).

Instead, the ABR (R2) generates a default route (0.0.0.0/0) for reachability outside the area.

R6 is in a stub area, so it cannot import external routes. ✅

Totally Stub Area (Area 2 - Contains R3, R4)

Totally stub areas block both external routes (Type-5 LSAs) and inter-area routes (Type-3 LSAs).

Only a default route (0.0.0.0/0) is injected by the ABR (R2).

R3 is in a totally stub area, so it cannot import external routes. ✅

R4, however, is just inside the totally stub area but is not restricted from generating external routes itself. ❌ (R4 can import external routes)

NSSA (Area 3 - Contains R5)

NSSAs allow external routes (Type-7 LSAs) but do not accept standard external routes (Type-5 LSAs) from other areas.

R5, being in an NSSA, can import external routes but only as Type-7 LSAs. ❌ (R5 can import external routes)

Final Answer: ✅ R3, R6 (Option A, C)

References:

HCIP-Datacom-Advanced Routing & Switching Technology V1.0 – OSPF Stub, Totally Stub, and NSSA Areas

OSPF LSA Types and External Route Restrictions

Comprehensive and Detailed In-Depth Explanation:

To determine the correct answers, we need to analyze OSPFv3 behavior and Inter-Area-Prefix LSAs (Type 3 LSAs).

1. Understanding OSPFv3 Inter-Area-Prefix LSAs (Type 3 LSAs)

Type 3 LSAs (Inter-Area-Prefix LSAs) are generated by an ABR (Area Border Router) to advertise networks between areas.

If a router in one area learns a prefix from another area, it generates a Type 3 LSA to advertise it further.

Stub areas (Area 1) do not allow external LSAs, including Type 3 LSAs for external routes.

NSSA areas (Area 3) accept external routes but redistribute them as Type 7 LSAs before being converted to Type 5 LSAs by an NSSA ABR.

2. Analyzing Each Answer Option:

✅ A. "The Inter-Area-Prefix-LSA that is generated by R1 and describes 2000::6/128 exists in Area 0." → TRUE

R6 has 2000::6/128 in Area 2.

R2 is the ABR that brings this prefix into Area 0 as a Type 3 LSA.

R1, being in Area 0, learns this LSA from R2.

Thus, this statement is correct.

❌ B. "The Inter-Area-Prefix-LSA that is generated by R1 and describes 2000::6/128 exists in Area 3." → FALSE

R1 is not an ABR for Area 3, so it does not generate an LSA for 2000::6/128 in Area 3.

Instead, R3 (the ABR between Area 0 and Area 3) would be responsible for propagating routes.

This statement is false.

❌ C. "The Inter-Area-Prefix-LSA that is generated by R2 and describes 2000::6/128 exists in Area 1." → FALSE

Area 1 is a stub area and does not accept external LSAs (including Type 3 LSAs from other areas).

R2 cannot generate and send a Type 3 LSA for 2000::6/128 into Area 1.

This statement is false.

✅ D. "The Inter-Area-Prefix-LSA that is generated by R3 and describes 2000::6/128 exists in Area 2." → TRUE

R3 is an ABR and learns 2000::6/128 from R2 (which originally learned it from R6 in Area 2).

Since Area 2 is a normal (non-stub, non-NSSA) area, Type 3 LSAs are allowed.

R3 generates and advertises this Inter-Area-Prefix-LSA for 2000::6/128 into Area 2.

Thus, this statement is correct.

Comprehensive and Detailed In-Depth Explanation:

Key OSPF Concepts to Consider:

Area 1 is an NSSA (Not-So-Stubby Area):

NSSAs allow external routes but advertise them as Type-7 LSAs.

The ABR (R2) converts these Type-7 LSAs into Type-5 LSAs for the backbone (Area 0).

Area 2 is a Stub Area:

Stub areas do not allow external routes (Type-5 LSAs).

This means that R5 (inside Area 2) will NOT receive external routes like 10.0.4.4/32 or 10.0.4.0/24.

Effect of asbr-summary 10.0.4.0 255.255.255.0 on R1 and R3:

This command ensures that R1 and R3 will see a summarized route 10.0.4.0/24 instead of specific /32 routes.

Routing Table Analysis:

R1 (ABR for NSSA, with ASBR summary configured)

Connected to Area 1 (NSSA) and Area 0 (Backbone)

Since asbr-summary 10.0.4.0 255.255.255.0 is configured on R1, it contains both 10.0.4.4/32 (from R4) and the summarized 10.0.4.0/24.

✅ Matches Option 4: The routing table contains both 10.0.4.4/32 and 10.0.4.0/24.

R5 (Inside Area 2 - Stub Area)

Stub areas do not receive external routes (Type-5 LSAs).

Since R5 is inside a stub area, it does not contain 10.0.4.4/32 or 10.0.4.0/24.

✅ Matches Option 3: The routing table does not contain 10.0.4.4/32 or 10.0.4.0/24.

R2 (ABR between NSSA and Backbone, but no ASBR summary configured)

R2 converts Type-7 LSAs from R4 into Type-5 LSAs and advertises them into Area 0.

Since no ASBR summary is configured on R2, it only sees the specific external route 10.0.4.4/32 but not the summarized 10.0.4.0/24.

✅ Matches Option 1: The routing table contains 10.0.4.4/32 only.

R3 (Another ABR with ASBR summary configured)

R3 has asbr-summary 10.0.4.0 255.255.255.0 configured, which means it will summarize the external routes.

Instead of 10.0.4.4/32, R3 will only have the summarized 10.0.4.0/24 route.

✅ Matches Option 2: The routing table contains 10.0.4.0/24 only.

References:

HCIP-Datacom-Advanced Routing & Switching Technology V1.0 – OSPF Areas (Stub, NSSA, and Backbone)

OSPF External Route Advertisement and Summarization

OSPF NSSA Behavior and Type-7 to Type-5 Conversion

Comprehensive and Detailed In-Depth Explanation:

Understanding the BGP and OSPF Network Topology in the Question:

External Route Importation

R1, R2, and R3 import 192.168.1.0/24 into BGP from an external source.

This means R1, R2, and R3 will advertise this route to their EBGP and iBGP peers.

BGP Route Selection Criteria

BGP follows specific rules to determine the best path for a route. The most relevant factors here are:

Highest Local Preference (LOCAL_PREF) → Preferred

Shortest AS Path → Preferred

Lowest Origin Type (IGP < EGP < Incomplete) → Preferred

Lowest MED (Multi-Exit Discriminator) → Preferred

Oldest eBGP route (if paths are equal) → Preferred

Route Selection Analysis for Each Statement:

A. For 192.168.1.0/24, R5 preferentially selects the route received from R2. ✅ (Correct)

R5 is in AS 65456 and peers with R6 using iBGP.

Since R2 is a central router with direct connectivity to R5, it is the most preferred path compared to indirect paths from R1 or R3.

By default, R5 will prefer the path from R2 over others unless explicitly influenced by BGP attributes.

✅ Statement A is correct.

B. For 192.168.1.0/24, R4 preferentially selects the route received from R1. ❌ (Incorrect)

R4 and R5 use Loopback0 to establish iBGP with R6, meaning they receive BGP routes from multiple sources.

BGP prefers the shortest AS path, and there is no specific information indicating that R1’s path is the shortest for R4.

R4 may actually prefer another router's advertisement (e.g., R2 or R3) depending on AS path length and other attributes.

❌ Statement B is incorrect.

C. For 192.168.1.0/24, if the default local-preference 150 command is configured on R3, R5 preferentially selects the route received from R3. ✅ (Correct)

By default, BGP assigns a local-preference of 100.

If R3 sets local-preference to 150, it is higher than other routes (R1, R2).

BGP prefers the highest local-preference value, so R5 will prefer the route received from R3 if this attribute is set.

✅ Statement C is correct.

D. For 192.168.1.0/24, R6 preferentially selects the route received from R4. ❌ (Incorrect)

R6 is an iBGP peer of both R4 and R5.

BGP best-path selection depends on attributes like local-preference, AS-path, and MED.

There is no explicit information suggesting that R4’s advertisement is preferred over R5’s.

R6 may prefer R5’s route depending on attributes.

❌ Statement D is incorrect.

Final Conclusion:

✅ A. R5 preferentially selects the route received from R2.❌ B. R4 does not necessarily prefer R1’s route.✅ C. If R3 sets local-preference 150, R5 will prefer the route from R3.❌ D. R6 does not necessarily prefer R4’s route.

Thus, the correct answers are: A, C.

Comprehensive and Detailed In-Depth Explanation:

Understanding Intra-Area-Prefix-LSA (Type 9) in OSPFv3

OSPFv3 uses the Intra-Area-Prefix-LSA (Type 9) to advertise IPv6 prefixes associated with either:

A Router-LSA (Type 1) → Describes links and interfaces.

A Network-LSA (Type 2) → Advertises multi-access networks (if a Designated Router exists).

Each router generates one Intra-Area-Prefix-LSA to advertise its own IPv6 prefixes.

Prefix Analysis for Each Router

R1's IPv6 Prefixes:

2000:12::1/64

2001:12::1/64

2002:12::1/64

2003:12::/64 (Shared link with R2)

Total Prefixes in R1’s Intra-Area-Prefix-LSA = 4

✅ R1 advertises four prefixes in its Intra-Area-Prefix-LSA.

R2's IPv6 Prefixes:

2003:12::2/64 (Shared link with R1)

Total Prefixes in R2’s Intra-Area-Prefix-LSA = 1

✅ R2 advertises only one prefix in its Intra-Area-Prefix-LSA.

Checking Each Option:

✅ A. The Intra-Area-Prefix-LSA generated by R2 describes three prefixes. (❌ False, R2 only has one prefix).

✅ B. The Intra-Area-Prefix-LSA generated by R1 describes four prefixes. (✔ True, R1 has four prefixes).

✅ C. The Intra-Area-Prefix-LSA generated by R2 describes four prefixes. (❌ False, R2 only has one prefix).

✅ D. The Intra-Area-Prefix-LSA generated by R1 describes three prefixes. (❌ False, R1 has four prefixes).

Final Conclusion:

✅ B. The Intra-Area-Prefix-LSA generated by R1 describes four prefixes.

Thus, the correct answer is: B. The Intra-Area-Prefix-LSA generated by R1 describes four prefixes.

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:

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.

To determine the correct command, we need to analyze BGP behavior in a Hub-Spoke topology and how routes are advertised in MPLS VPN environments.

1. Understanding the Hub-Spoke BGP/MPLS VPN Topology

The network consists of Hub-PE and Spoke-PE routers, which are MPLS VPN PEs.

Hub-PE is responsible for distributing routes between Spoke-PE1 and Spoke-PE2.

Spoke routers do not have direct IBGP peering with each other; instead, they rely on the Hub-PE to relay routes.

BGP next-hop handling is critical for proper route advertisement.

2. Why is the "next-hop-self" Command Required?

By default, when BGP advertises a route, the next-hop remains unchanged (i.e., the original next-hop is retained).

In Hub-Spoke topology, Spoke routers would receive routes with a next-hop IP that belongs to another Spoke-PE, which is not reachable directly.

To solve this issue, we use the next-hop-self command on the Hub-PE, so that:

Hub-PE updates the next-hop to its own address before advertising routes to the Spoke-PEs.

This ensures that Spoke-PE routers use the Hub-PE as the next-hop, making routes reachable and preventing blackholing.

3. Correct Command Usage

The administrator must run the following command under the BGP IPv4 address family of the BGP-VPN_out instance on Hub-PE:

shell

CopyEdit

peer 10.1.2.1 next-hop-self

This ensures that the next-hop for advertised routes is changed to the Hub-PE's IP, allowing proper route transmission in the Hub-Spoke MPLS VPN environment.

Comprehensive and Detailed In-Depth Explanation:

1. Understanding OSPF Neighbor Relationships

OSPF (Open Shortest Path First) forms neighbor relationships based on these key conditions:

Routers must be in the same OSPF area.

The subnet mask and network type must match.

The Hello/Dead timers must match.

Authentication (if enabled) must match.

2. Analyzing the Given Scenario

R1 and R2 are in Area 0 (Backbone Area).

R3 and R4 are in Area 1 (Non-Backbone Area).

R4 was configured incorrectly using R3’s backup configuration, which could cause issues.

3. Evaluating Each Answer Option

Option A: "The OSPF neighbor relationship between R1 and R2 is not affected."

Correct.

R1 and R2 are both in Area 0 and their configuration was not changed.

Since R4 was added only between R2 and R3, it does not impact R1 and R2.

✅ A is correct.

Option B: "An OSPF neighbor relationship can be established between R2 and R4."

Incorrect.

R2 is in Area 0, but R4 is incorrectly configured using R3’s backup, which likely placed it in Area 1.

OSPF neighbors cannot form across different areas unless an Area Border Router (ABR) is properly configured.

Since there is no indication of an ABR setup, the adjacency will fail.

❌ B is incorrect.

Option C: "An OSPF neighbor relationship can be established between R3 and R4."

Correct.

R3 and R4 are both in Area 1, and R4's backup configuration comes from R3, meaning they likely have identical settings.

Since they share the same area and are directly connected, an OSPF adjacency is possible.

✅ C is correct.

Option D: "An OSPF neighbor relationship can be established between R1 and R3."

Incorrect.

R1 is in Area 0, and R3 is in Area 1.

OSPF does not form neighbor relationships between different areas unless configured as an ABR, which is not mentioned.

❌ D is incorrect.

Final Answer:

✅ A and C are correct.

HCIP-Datacom-Advanced Routing & Switching Technology References:

OSPF Neighbor Formation and Area Design Principles

Troubleshooting OSPF Area Mismatches and Configuration Issues

OSPF Backbone Area (Area 0) and Inter-Area Communication

Comprehensive and Detailed In-Depth Explanation:

Understanding the OSPF Network Structure in the Question:

OSPF Areas & Routers:

Area 3: Contains R5 (which has loopback 10.0.5.5/32).

Area 1: Contains R6.

Area 2: Contains R4.

Area 0 (Backbone Area): Contains R1, R2, and R3 (which interconnect the other areas).

ACL 2000 Filtering Rule:

The ACL rule 2000 explicitly denies 10.0.5.5/32 from being imported.

The filter 2000 import command applies this filter to Area 0, preventing routes from Area 3 (including R5's loopback) from being learned by Area 0 routers (R1, R2, and R3).

Route Distribution Analysis:

R5 (Area 3):

R5 has 10.0.5.5/32 configured on its Loopback0.

Since OSPF is enabled, R5 advertises the route to R6 in Area 1.

R6 (Area 1) → R2 (Area 0, Backbone Router):

Without filtering, R6 would normally propagate 10.0.5.5/32 to R2 (since R2 is a backbone router in Area 0).

However, since ACL 2000 is applied in Area 0, R2 blocks this route from being imported.

Therefore, R2 does not learn 10.0.5.5/32.

R2 → R1 and R3 (Both in Area 0):

R2 would typically share any learned routes with R1 and R3 in Area 0.

But since R2 itself does not have 10.0.5.5/32, neither R1 nor R3 can receive it.

Thus, R1 and R3 also do not have 10.0.5.5/32 in their routing tables.

R4 (Area 2) is Unaffected:

Since R4 is in Area 2, it is not directly impacted by the filter applied in Area 0.

It can still receive the route via another path if redistribution is configured properly.

Final Conclusion:

R1, R2, and R3 do not have the 10.0.5.5/32 route due to the filter 2000 import command applied in Area 0.

R4 may still have the route since it is not affected by the filtering in Area 0.

Thus, the correct answer is:✅ R1, R3, R2 do not have the route 10.0.5.5/32 in their routing tables.

Comprehensive and Detailed In-Depth Explanation:

Understanding the IS-IS Network Structure in the Question:

Router Roles & IS-IS Levels:

R1 and R3: Level-1 routers.

R2: Level-1-2 router (interconnects Level-1 and Level-2 areas).

R4: Level-2 router.

Key Command Used: default-route-advertise always level-1

This command forces R1 to advertise a default route (0.0.0.0/0) to all Level-1 routers.

In an IS-IS network:

Level-1 routers do not see Level-2 routes unless a default route is provided.

The default route is propagated only within the Level-1 area and does not affect Level-2 routers unless explicitly redistributed.

Route Distribution Analysis:

R1 (Level-1) imports the default route and advertises it to all Level-1 routers.✅ R1 has the default route.

R3 (Level-1) is in the same Level-1 area as R1, so it receives the default route from R1.✅ R3 has the default route.

R2 (Level-1-2) connects Level-1 and Level-2. Since it participates in Level-1, it also learns the default route from R1.✅ R2 has the default route.

R4 (Level-2) is not in Level-1 and does not receive the default route unless it is explicitly redistributed from Level-1 to Level-2, which is not stated in the question.❌ R4 does NOT have the default route.

Final Conclusion:

R1, R2, and R3 have the default route.

R4 does not have the default route.

Thus, the correct answer is:✅ R1, R2, and R3 have the default route in their routing tables.