Huawei H12-821_V1.0 - HCIP-Datacom-Core Technology V1.0

The filter-policy command in IS-IS is used to control the advertisement and filtering of routing information. However, it does not directly filter LSPs (Link State Packets); instead, it controls route advertisements. The false statement here is that it filters LSPs ​.

BFD control packets are encapsulated in UDP packets, and the destination port number for multi-hop BFD control packets is 4784. This is a standardized port for multi-hop BFD operation ​.

Comprehensive and Detailed in-depth Step-by-Step Explanation:

To understand this question, let ' s first review the functional planes in network devices, particularly Huawei switches:

Control Plane :

The control plane is responsible for generating and maintaining routing tables and forwarding entries.

It uses protocols like OSPF, BGP, and RIP to exchange routing information with other network devices. Once the routing information is processed, it installs forwarding entries into the forwarding plane for actual packet forwarding.

On Huawei switches, the control plane is mandatory for building and updating the forwarding table. Without it, the data plane cannot forward traffic correctly.

Forwarding Plane (or Data Plane) :

This plane handles the actual forwarding of packets based on the forwarding table created by the control plane.

The forwarding plane operates at high speed to ensure that traffic flows efficiently.

Monitoring Plane :

This plane is responsible for network management and monitoring. It gathers statistics and provides tools for troubleshooting and visibility.

In this case, the control plane provides the routing information and forwarding entries required for the data plane to perform packet forwarding. Therefore, the correct answer is B. Control plane.

Comprehensive and Detailed Step-by-Step Explanation:

1. What is VRF (Virtual Routing and Forwarding)?

VRF is a network virtualization technology that enables multiple isolated routing tables to coexist on a single physical device.

Each VRF instance is independent, which ensures separation between different VPNs or users.

2. Resources That VRF Can Independently Own:

Option A: Interface

Correct.

Each VRF instance can have its own set of interfaces. These interfaces are bound to a specific VRF, isolating traffic at the physical or logical port level.

Option B: Routing table

Correct.

VRF instances maintain independent routing tables. This ensures that routes for one VPN do not overlap or interfere with routes of another VPN.

Option C: MAC address table

Incorrect.

The MAC address table is part of Layer 2 operations and is shared by all VRF instances on the device. VRF operates at Layer 3 and does not isolate MAC address tables.

Option D: Routing protocol process

Correct.

Each VRF instance can run its own routing protocol processes (e.g., OSPF, BGP), and these processes are completely independent of other VRF instances.

3. Summary:

The correct resources that can be independently owned by a VRF instance are Interface , Routing Table , and Routing Protocol Process .

A stateful inspection firewall tracks the state of active connections. If a packet matches an existing session in the firewall ' s state table, it is allowed to pass. The diagram indicates that the TCP packet matches the session state, so the firewall forwards it ​.

Let ' s break it down step by step based on Huawei ' s routing protocol behavior:

R1 imports the direct route 10.1.1.0/24 into OSPF .

This route is advertised by R1 to R2 and R3 via OSPF .

Both R2 and R3 are running IS-IS , and bidirectional route redistribution is configured between OSPF and IS-IS.

R2 and R3 both re-advertise the OSPF-learned route into IS-IS and then potentially re-learn it back from the IS-IS domain, causing redistribution loops unless properly controlled.

Now, the question focuses on R3’s routing table :

R3 already learns the route directly via OSPF from R1.

It also learns the same route again via IS-IS from R2 (looped back due to bidirectional redistribution).

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

“OSPF ASE routes are assigned a default preference of 150. If a route is redistributed from another protocol (like IS-IS) into OSPF, and then re-learned, it is considered an ASE route.” (Chapter: OSPF Advanced Features – Section: Route Redistribution Behavior)

The sequence of steps for electing the root port in an STP (Spanning Tree Protocol) network is as follows:

Bridge ID Comparison : The Bridge ID (BID) is compared between the bridges in the network. A smaller value indicates a higher priority, meaning the bridge with the lowest Bridge ID is elected as the root bridge.

RPC (Root Path Cost) Comparison : The path cost to reach the root bridge is calculated. The router with the lowest Root Path Cost (RPC) to the root bridge will have a higher priority for the election of the root port.

Peer BID Comparison : If there is a tie in the Root Path Cost, the Peer BID is compared. A smaller Peer BID indicates a higher priority. This step ensures that if two routers have the same RPC, the one with the lower Peer Bridge ID wins.

Local BID Comparison : If there is still a tie, the Local BID is compared. A smaller Local BID indicates a higher priority. This final step ensures that the router with the lowest local identifier is selected.

Bridge ID Comparison : The first step in electing the root port is comparing the Bridge IDs. The bridge with the lowest Bridge ID becomes the root bridge . The Bridge ID is made up of the bridge priority and MAC address . The root bridge is the center of the network for STP, and all other ports will calculate their paths based on this root.

In BGP, the AS-Path attribute is mandatory and must be included in all UPDATE messages. It records the autonomous systems a route has traversed. Attributes like Local-Preference , MED , and Prefval are optional and may not always be included. The AS-Path is crucial for loop prevention and route selection ​.