Free Practice Questions for Huawei H12-831_V1.0 Exam

Restrict → Discards the packets that trigger static MAC address flapping and reports an alarm.

Protect → Discards the packets that trigger static MAC address flapping only and does not report an alarm.

Shutdown → Sets the interface state to error-down and reports an alarm.

Comprehensive and Detailed In-Depth Explanation:

1. Understanding Port Security Modes

Port security is used to control access on a switch port based on MAC addresses. If a MAC address violation occurs (e.g., static MAC address flapping), the switch can take different actions based on the configured security mode.

Security Mode

Description

Restrict

Drops the violating packets and logs the violation by generating an alarm.

Protect

Drops the violating packets but does not generate an alarm.

Shutdown

Places the interface into error-disabled (error-down) state and logs an alarm.

2. Matching Each Security Mode with Its Operation

Protect Mode:

The switch drops the packets from the unauthorized MAC address.

No alarm is generated or logged.

Correct Mapping: "Discards the packets that trigger static MAC address flapping only and does not report an alarm."

Restrict Mode:

The switch drops the packets from the unauthorized MAC address.

An alarm is generated and logged in the system.

Correct Mapping: "Discards the packets that trigger static MAC address flapping and reports an alarm."

Shutdown Mode:

The switch shuts down the interface by placing it into the error-down state.

An alarm is generated and logged.

Correct Mapping: "Sets the interface state to error-down and reports an alarm."

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:

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:

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.

To determine the correct answer, we need to analyze how OSPFv3 handles Router LSAs (Type 1 LSAs) in a simple Area 0 topology like the one shown in the figure.

1. Understanding OSPFv3 Router LSAs (Type 1 LSAs)

Router LSAs (Type 1 LSAs) are generated by each router within an OSPF area to describe its own directly connected links.

Each router in an OSPF area generates exactly one Type 1 LSA.

The Link-State Database (LSDB) on a router contains LSAs from all routers in the same area.

2. Analyzing the Network in the Figure

There are 3 routers: R1, R2, and R3.

All routers are in OSPFv3 Area 0 (which is a single area).

Each of these routers generates one Router LSA (Type 1 LSA).

Since R2 is in the same area as R1 and R3, its LSDB contains the Router LSAs from itself, R1, and R3.

3. Conclusion

The LSDB of R2 contains 3 Router LSAs (one from each router: R1, R2, and R3).

Final Answer: 3

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.