Huawei Updated H12-821_V1.0 Exam Questions and Answers by macy

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.

 During WLAN roaming, the STA sends a Reassociation Request frame to the foreign AP to maintain connectivity. Association frames are used during initial connections, not roaming.

 APs with which a STA is associated before and after roaming can work on different channels, as roaming often occurs across channels in environments like multi-SSID or multi-channel setups.Options C and D are false, as they contradict standard WLAN roaming procedures ​.

IPv4 supports three main transmission modes:

Unicast: One-to-one communication.

Broadcast: One-to-all communication within a network.

Multicast: One-to-many communication to a group of interested receivers.Anycast is not a native IPv4 mode but is introduced in IPv6 ​.

Comprehensive and Detailed in-depth Step-by-Step Explanation:OSPF routers establish neighbor relationships and progress through various states during the adjacency formation process. The ExStart state is where routers negotiate the master and slave roles. This negotiation is critical because the master initiates the Data Description (DD) packet exchange process.

Here’s a breakdown of the relevant OSPF states:

ExStart State:

This is the phase where the routers determine which one will act as the master and which will be the slave.

The decision is based on the Router IDs of the two routers. The router with the higher Router ID becomes the master.

Exchange State:

After the master-slave roles are established, the routers exchange DD packets. These packets contain summaries of the LSAs in their respective LSDBs.

2-way State:

This state indicates that bidirectional communication has been established between the two routers, but it occurs before master-slave negotiation.

Init State:

This is an early state where a router has sent a Hello packet to its neighbor but has not yet received a Hello packet in response.

Key Point:The negotiation of master and slave roles happens exclusively in the ExStart state, making D. ExStart the correct answer.

References:

Huawei HCIA-Datacom Study Guide, Chapter on "OSPF Neighbor States".

RFC 2328 – OSPF Version 2 (Section 10.8).