Free Huawei H12-821_V1.0 Practice Exam with Questions & Answers | Set: 10

Comprehensive and Detailed Step-by-Step Explanation:

1. Overview of BGP:

BGP (Border Gateway Protocol) is an Exterior Gateway Protocol (EGP) designed to exchange routing information between different Autonomous Systems (ASs) on the internet. Unlike traditional distance-vector protocols (like RIP), BGP is considered a path-vector protocol, as it not only determines reachability but also ensures policy-based routing decisions and advanced path selection mechanisms.

2. Analysis of Each Option:

Option A: BGP does not support authentication. Therefore, it cannot ensure network security.

This statement is incorrect .

BGP supports authentication using mechanisms such as TCP MD5 (Message Digest 5) and TCP-AO (Authentication Option). These authentication mechanisms ensure that BGP messages are not tampered with or intercepted during transmission, enhancing network security.

In OSPF, Database Description (DD) packets are used during the database synchronization process. In the first DD packet a router sends during neighbor establishment, three control bits are set:

I bit (Initial) = 1 → This indicates that the DD packet is the first in the sequence.

M bit (More) = 1 → This means more DD packets will follow.

MS bit (Master/Slave) = 1 → Set by the router assuming the master role in the exchange process.

Setting all three bits to 1 is a standard part of the DD exchange initiation.

Reference from Huawei HCIP-Datacom-Core Technology Study Guide:

“In the initial DD packet, the I, M, and MS bits are set to 1 by the master router initiating database exchange.”

(Chapter: OSPF Operation Mechanism – Section: Neighbor State Machine)

Comprehensive and Detailed In-Depth Explanation:

Spanning Tree Protocol (STP) has long convergence times due to Listening and Learning states .

Rapid Spanning Tree Protocol (RSTP) introduces:

Proposal/Agreement (P/A) mechanism → Allows ports to quickly transition to Forwarding state without waiting.

This mechanism significantly reduces convergence time in a switched network .

Since RSTP does use the P/A mechanism to accelerate port forwarding, the statement is true .

???? Reference: Huawei HCIA-Datacom Study Guide, STP vs. RSTP and P/A Mechanism.

A Totally Stubby Area in OSPF is a special type of stub area where only intra-area (Type 1) LSAs , router LSAs , and default routes (Type 3 LSA with 0.0.0.0/0) are allowed to be injected. It blocks inter-area routes (Type 3 LSAs for specific prefixes) and Type 5 LSAs (external routes) to reduce the size of the Link-State Database (LSDB) and enhance router performance.

Explanation of the Options:

A. Type 3 specific LSA – ❌ Correct Answer . These LSAs represent inter-area routes. Totally Stubby Areas do not allow Type 3 LSAs for specific routes , only for the default route (0.0.0.0/0).

B. Type 1 LSA – ✅ Allowed. These are Router LSAs generated by routers within the area and are necessary for OSPF to function.

C. Type 3 LSA that describes a default route – ✅ Allowed. This is the only Type 3 LSA permitted in a Totally Stubby Area. It provides a default route (0.0.0.0/0) to reach external destinations.

D. Type 2 LSA – ✅ Allowed if there are broadcast or NBMA networks in the area. These describe the network segment in multi-access environments and are generated by the DR.

Official Huawei Reference:

???? Huawei HCIP-Datacom-Core Technology Study Guide –

Chapter: OSPF Special Areas

" A totally stub area does not allow inter-area Type 3 LSAs or external Type 5 LSAs to enter. Only a default route is injected in the form of a Type 3 LSA (0.0.0.0/0), which greatly reduces the LSDB size. "

???? Also refer to:

Huawei VRP Command Guide > OSPF > Configuration Notes > OSPF Special Areas

Comprehensive and Detailed Step-by-Step Explanation:

Distance-Vector Protocols:

Distance-vector protocols determine the best path based on the distance to a destination and periodically share the entire routing table with neighbors.

Example: RIP is a distance-vector protocol.

Link-State Protocols:

Link-state protocols share information about directly connected links, enabling routers to build a complete map of the network.

OSPF (Open Shortest Path First) and IS-IS (Intermediate System to Intermediate System) are link-state protocols that use Dijkstra’s algorithm to calculate the shortest path.

Border Gateway Protocol (BGP):

BGP is neither a distance-vector nor a link-state protocol. Instead, it is classified as a path-vector protocol that selects the best path based on attributes such as AS-path, next-hop, and local preference.

1 – Idle

2 – Connect

3 – OpenSent

4 – OpenConfirm

5 – Established

6 – Active

The BGP finite state machine defines how a BGP speaker transitions through various states when establishing and maintaining a BGP session. Below is the role of each state:

Idle (1) – BGP is waiting to start a connection. Initial state of the BGP process.

Connect (2) – BGP initiates a TCP connection to the peer.

OpenSent (3) – TCP connection is established; BGP sends an OPEN message and waits for one from the peer.

OpenConfirm (4) – BGP has received a valid OPEN message and is now expecting a KEEPALIVE.

Established (5) – BGP session is fully established; UPDATE messages can now be exchanged.

Active (6) – If the TCP connection fails in Connect state, BGP transitions to Active and will retry connection.

Reference from Huawei HCIP-Datacom-Core Technology Study Guide:

“BGP goes through the following states in order: Idle → Connect → Active → OpenSent → OpenConfirm → Established. The transition depends on the success or failure of TCP connection setup and BGP message exchanges.”

(Chapter: BGP Principles – Section: BGP State Machine)

Comprehensive and Detailed In-Depth Explanation:

OSPF network types affect how protocol packets (Hello, LSA updates) are transmitted:

NBMA (Non-Broadcast Multi-Access) networks (e.g., Frame Relay) do not support multicast , so routers must unicast OSPF packets to neighbors.

Broadcast networks (e.g., Ethernet) support multicast and use 224.0.0.5 for Hello packets and 224.0.0.6 for DR/BDR communication .

The statement is false because:

NBMA does not unicast all packets —only Hello packets must be manually configured to be unicast.

LSAs and routing updates can still be multicast if an NBMA network is configured as point-to-multipoint .

???? Reference: Huawei HCIA-Datacom Study Guide, OSPF Network Types and Packet Transmission.

Master

Backup

Master

Backup