H12-831_V1.0 Huawei HCIP-Datacom-Advanced Routing & Switching Technology V1.0 Free Practice Exam Questions (2026 Updated)

LDP establishes and maintains sessions between Label Switching Routers (LSRs) to exchange label bindings and construct Label Switched Paths.

An LDP session relies on a TCP connection established using the transport addresses advertised by its participating routers.

Changing the LDP transport address affects the session ' s transport endpoint and can require the session to be terminated and re-established using the new address.

Changing the label advertisement mode also affects fundamental LDP negotiation and label distribution behaviour. Huawei documentation explicitly states that modifying this mode causes LDP sessions to be re-established.

Configuring Penultimate Hop Popping (PHP) changes label forwarding behaviour rather than the established LDP session itself.

Similarly, changing the MPLS TTL processing mode does not inherently require LDP session renegotiation.

Therefore, changing the LDP transport address and label advertisement mode are the applicable operations.

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A Layer 2 loop occurs when Ethernet frames circulate repeatedly through redundant switching paths without an effective loop-prevention mechanism.

Because Ethernet frames do not contain a TTL field equivalent to that used in IP packets, broadcast and unknown-unicast frames may continue circulating and multiplying.

This behaviour can create broadcast storms, causing excessive interface bandwidth utilization.

The resulting traffic volume can also overload the switch CPU, especially when large quantities of protocol or control packets are processed.

High CPU utilization can prevent administrators from logging in or cause the device to respond slowly to management operations.

Additionally, service interface indicators may blink unusually frequently because of the sustained traffic volume.

All four symptoms are consistent with Layer 2 loops. Huawei ' s troubleshooting documentation identifies these symptoms as indicators of switching loops.

OSPFv3 AS-External-LSAs advertise external IPv6 routing information across permitted OSPF areas.

The displayed LSA identifies the originating router as 10.0.3.3, confirming option C. The Route Tag field contains the value 1, confirming option B.

The LSA specifies Metric Type 2 with a metric of 1. For an E2 external route, the advertised external metric remains the primary route metric, while the internal cost to the ASBR can be used for tie-breaking. Therefore, option A describes the E2 metric behaviour.

Option D is not established by the exhibit. Although NSSA Type 7 LSAs can be translated into AS-External-LSAs by an ABR, the displayed Type 5 LSA does not independently demonstrate that translation occurred.

Consequently, the statements supported by the LSA are A, B, and C.

HCIP-Datacom-Advanced Routing & Switching Technology V1.0 Training Material.pdf

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Comprehensive and Detailed In-Depth Explanation:

1. Understanding DHCP Snooping

DHCP Snooping is a security feature that filters untrusted DHCP messages to prevent attacks such as:

Rogue DHCP servers distributing incorrect IP addresses.

DHCP starvation attacks.

In DHCP Snooping, switch ports are classified as:

Trusted Interfaces: Allow both DHCP requests and DHCP responses to pass through.

Untrusted Interfaces: Allow only DHCP requests but drop DHCP responses (to prevent rogue DHCP servers).

2. Analyzing Each Answer Option

Option A: " When receiving a DHCP response packet on GE0/0/2, the switch forwards the packet through GE0/0/1. "

Correct.

GE0/0/2 is a trusted interface (connected to the DHCP server).

DHCP responses (ACK, NAK, OFFER) come from the DHCP Server.

Since DHCP responses are allowed on trusted interfaces, the switch forwards them to the client (PC1) via GE0/0/1.

Option B: " When receiving a DHCP request packet on GE0/0/2, the switch forwards the packet through GE0/0/3. "

Incorrect.

DHCP requests originate from clients (PC1, attackers, etc.), not from the DHCP server.

The DHCP request should be forwarded to the DHCP server via a trusted interface (not GE0/0/3, which is untrusted).

Option C: " When receiving a DHCP response packet on GE0/0/3, the switch forwards the packet through GE0/0/1. "

Incorrect.

GE0/0/3 is an untrusted interface (connected to the attacker).

DHCP responses (ACK, OFFER) from untrusted interfaces are dropped to prevent rogue DHCP attacks.

The switch will not forward the packet.

Option D: " When receiving a DHCP request packet on GE0/0/3, the switch forwards the packet through GE0/0/2. "

Correct.

DHCP requests originate from clients (PC1 or attacker).

Since DHCP requests are allowed on untrusted interfaces, the switch forwards them to the DHCP server via the trusted interface (GE0/0/2).

Final Answer:

✅ A and D are correct.

HCIP-Datacom-Advanced Routing & Switching Technology References:

DHCP Snooping and Port Trust Classification

How Trusted and Untrusted Ports Handle DHCP Packets

Preventing Rogue DHCP Servers Using DHCP Snooping

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.

The option lettering in the supplied question is malformed. In the standard option order, the source-IP statement is option B, and it is the item that was not added for IS-IS IPv6.

Unlike OSPFv3, IS-IS operates directly over the data-link layer rather than being encapsulated in IPv4 or IPv6. Consequently, an IS-IS Hello PDU does not have an IP header or an IP source address that could be changed to an IPv6 link-local address.

To support IPv6 route processing, IS-IS was extended with the following information:

TLV 232 — IPv6 Interface Address: Carries one or more 128-bit IPv6 interface addresses.

TLV 236 — IPv6 Reachability: Carries IPv6 prefixes, metrics and reachability attributes.

IPv6 NLPID: The value 142 (0x8E) identifies IPv6 as a supported network-layer protocol and is carried when IPv6 reachability is advertised.

Therefore, TLV 232, TLV 236 and the IPv6 NLPID are valid IS-IS IPv6 extensions. Changing an IS-IS Hello packet’s source IP address is not one of them. Huawei IS-IS documentation