Free Huawei H12-811_V1.0 Practice Exam with Questions & Answers | Set: 8

Detailed Explanation:In a Layer 2 WLAN, an Access Controller (AC) typically handles authentication and management but does not act as a gateway. Instead, a Layer 3 device, such as a router, serves as the gateway. (Reference: HCIA-WLAN Training Material, WLAN Layer 2 and Layer 3 Concepts)

Network Layers in Campus Design:

The three common layers in a campus network are:

Core Layer: Provides high-speed backbone connectivity.

Aggregation Layer: Consolidates traffic and applies policies.

Access Layer: Connects end devices like PCs and phones.

Why "Network Layer" Is Incorrect:

"Network layer" is not a term used to describe physical or logical architecture in campus networks. It refers to Layer 3 in the OSI model, which is about IP routing.

Why Other Options Are Correct:

Core, access, and aggregation layers are widely used in hierarchical network design.

References: HCIA-Datacom V1.0 Certification Guide, Chapter 4: Campus Network Design.

Comprehensive Explanation: When Router A forwards the packet to Router B, the destination IP address (11.0.12.1) remains unchanged as it is still meant for Host B. However, the destination MAC address changes to MAC-B, which belongs to Host B, since MAC addresses are only used for local network hops​

Comprehensive and Detailed Explanation:

BPDU (Bridge Protocol Data Unit) packets are exchanged only on ports in Blocking, Listening, and Learning states.

Ports in Forwarding state DO NOT receive BPDU packets (BPDUs are only processed by non-designated ports).

If a forwarding port starts receiving BPDUs, it goes back to Listening state to re-evaluate STP topology.

✅ Reference: HCIA-Datacom Switching Guide – STP Port States

Detailed Explanation:The TCP protocol ensures reliable data transmission by using a three-way handshake to establish a connection and a four-way handshake to terminate it. This handshake process helps ensure that both parties are synchronized and agree on communication parameters before data transmission begins. Additionally, mechanisms such as sequence numbers and acknowledgments ensure that data is received correctly and in order .

Comprehensive and Detailed Explanation:

OSPF DR/BDR election criteria:

Highest Priority (default is 1, 0 means ineligible).

Highest Router ID (if priorities are equal).

Given the routers in the figure:

Router A (RID 10.0.1.1, Priority 255) → Elected DR.

Router B (RID 10.0.2.2, Priority 0) → Not eligible for DR/BDR.

Router C (RID 10.0.3.3, Priority 0) → Not eligible for DR/BDR.

Since no other router has a nonzero priority, no BDR is elected.

✅ Reference: HCIA-Datacom Routing Guide – OSPF DR/BDR Election Process

In the given network diagram, we have three routers (Router A, Router B, and Router C) connected in a multi-access network (likely an Ethernet segment, as indicated by the shared line connecting all three routers). The election of the Backup Designated Router (BDR) in an OSPF (Open Shortest Path First) network follows strict rules defined in RFC 2328 and reinforced in the HCIA Datacom documentation. Let’s break it down step by step:

OSPF Roles in a Multi-Access Network:In OSPF, a multi-access network (e.g., Ethernet) elects a Designated Router (DR) and a Backup Designated Router (BDR) to reduce the number of adjacencies and optimize network traffic. The DR and BDR are responsible for maintaining the link-state database and flooding LSAs (Link State Advertisements) on behalf of other routers in the segment.

Election Process for DR and BDR (Strict OSPF Rules – RFC 2328):The election process is based on the following criteria (in order of precedence):

Router Priority: A higher priority value (configurable, default is 1, range 0–255) wins. A router with a priority of 0 is ineligible to become a DR or BDR.

Router ID (RID): If priorities are equal (and non-zero), the router with the highest RID wins. The RID is a unique 32-bit identifier, typically the highest IP address on the router’s loopback interface or the highest active physical interface IP address.

The router with the highest priority (or highest RID if priorities are tied) becomes the DR, and the router with the second-highest priority (or RID) becomes the BDR. A router with a priority of 0 is explicitly excluded from the DR/BDR election and cannot participate, even if it has the highest RID.

Analyzing the Given Data:

Router A: Router ID = 10.0.1.1, Priority = 255

Router B: Router ID = 10.0.2.2, Priority = 0

Router C: Router ID = 10.0.3.3, Priority = 0

The diagram shows a multi-access network with all three routers connected, suggesting an OSPF environment where DR/BDR election occurs.

Applying Strict OSPF Election Rules:

First, we evaluate the priorities:

Router A has a priority of 255, which is the highest possible value, ensuring it is elected as the DR.

Router B and Router C both have a priority of 0, making them ineligible to become either DR or BDR, regardless of their Router IDs.

Since Router A is the DR (due to its priority of 255), we need to elect a BDR from the remaining routers (Router B and Router C). However, both Router B and Router C have priorities of 0, which, per RFC 2328 and HCIA Datacom, explicitly prevents them from being elected as DR or BDR.

Therefore, no router is eligible to become the BDR in this scenario, resulting in "No BDR" for the network.

Resolving Potential Misinterpretations:

In my previous explanation, I suggested Router C could be elected as BDR based on its higher RID (10.0.3.3) compared to Router B (10.0.2.2), even though both had priority 0. This was incorrect and inconsistent with strict OSPF rules. RFC 2328 (Section 9.4) and HCIA Datacom V3.0 (Chapter 5: OSPF Protocol) clearly state that a router with a priority of 0 cannot participate in the DR/BDR election, and its RID is irrelevant for this purpose.

The HCIA Datacom documentation emphasizes adherence to OSPF standards, and in practice, if all routers except the DR have a priority of 0, the network operates with only a DR and no BDR. This is a valid OSPF configuration, though not ideal for redundancy, as the BDR role remains unassigned until a router with a non-zero priority joins the network.

Conclusion:

Router A is elected as the DR due to its priority of 255.

Router B and Router C have priorities of 0, making them ineligible to become BDR.

Therefore, there is no BDR elected in this network, and the correct answer is "No BDR" (option A).

References from HCIA Datacom Documents and RFC:

HCIA Datacom V3.0, Chapter 5: OSPF Protocol – DR/BDR Election Process

RFC 2328 (OSPF Version 2) – Section 9.4: DR and BDR Election (specifically, the rule that a router with priority 0 is ineligible for DR/BDR roles)

Huawei OSPF Configuration Guide (HCIA Datacom Certification Material) – Priority and Router ID in Multi-Access Networks

Switch Forwarding Behavior:

If the destination MAC is not found in the MAC address table, the switch floods the frame.

Broadcasting Within VLANs:

VLAN tagging ensures the frame remains within its designated VLAN.

The frame is not sent to all interfaces but only within the VLAN.

Why Other Options Are Incorrect:

A: Does not consider VLAN segmentation.

C: Switches do not discard unknown unicast frames unless configured to do so.

D: Includes access interfaces only, but flooding happens on all VLAN interfaces.

Conclusion:

The switch floods the frame within the VLAN, making the correct answer B.

References: HCIA-Datacom V1.0 Certification Guide, Chapter 4: Switch Forwarding Mechanisms.

The PVID (Port VLAN ID) specifies the default VLAN for untagged frames.

The command port trunk pvid vlan 10 means that VLAN 10 is the default VLAN.

When untagged frames arrive, they are assigned to VLAN 10.

When the switch forwards frames from VLAN 10, it removes the VLAN tag.

VLANs 20, 30, and 40 remain tagged.

Thus, the correct answer is D (VLAN 10).