Free Practice Questions for Huawei H12-821_V1.0 Exam

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.

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

The Network Entity Title (NET) is a unique identifier assigned to an IS-IS router. It is derived from the Network Service Access Point (NSAP) address and consists of the following components:

Area Address:

Identifies the area in which the router resides.

Multiple routers in the same IS-IS area must have the same area address.

System ID:

Uniquely identifies the router within the IS-IS area.

The System ID is typically derived from the router's loopback IP address or another unique value.

SEL (Selector Field):

The SEL field is always set to 00 for IS-IS NETs.

The NET is used by IS-IS for route calculation and to identify the router within the IS-IS domain. Therefore, the statement is TRUE.

 MQC and PBR

MQC (Modular QoS Command-Line Interface): Applied to interfaces for classifying and controlling traffic.

PBR (Policy-Based Routing): Used to influence packet forwarding based on policies rather than traditional routing tables.

Both MQC and PBR can be configured on device interfaces to filter incoming/outgoing packets or control their forwarding paths.

 HCIP-Datacom-Core Reference

The use of MQC and PBR on device interfaces is elaborated in the QoS and routing control chapters​​.

1. Understanding Prefix List Configuration:

The command ip ip-prefix huawei index 10 permit 10.1.1.0 24 greater-equal 26 defines a prefix filter:

The base prefix is 10.1.1.0/24.

The greater-equal 26 condition specifies that the mask length of matching prefixes must be at least 26 bits.

If the less-equal parameter is not explicitly defined, the default value is 32, meaning the longest possible mask length for IPv4.

2. Explanation of Values:

greater-equal-value: Specifies the minimum mask length. In this case, the value is 26.

less-equal-value: Specifies the maximum mask length. Since it is not explicitly configured, the default value is 32.

3. Summary:

greater-equal-value = 26

less-equal-value = 32

Huawei HCIA-Datacom Study Guide, Chapter "IP Prefix List Configuration."

Goal Analysis:

Requirement:

The route to 192.168.3.0/24 must exist in R1's and R3's routing tables.

The route must not exist in R2's routing table.

This requires filtering to ensure the route is either:

Blocked on R2's routing table (via filtering on R2), or

Blocked before it is advertised to R2.

Analysis of Each Option:

Option A (Filter-policy on R2 for filtering received routes):

Applying a filter-policy on R2 to filter received routes will block the route from entering R2's routing table but still allow it to propagate to R3.

This meets the requirement.

Option B (Filter-policy on R2 for filtering the routes to be advertised):

Blocking the advertisement of routes from R2 to other routers does not affect the routes received by R2 itself.

This does not meet the requirement but does not affect the propagation to R3.

This is valid if the received route is blocked.

Option C (Filter-policy on R1 for filtering the routes to be imported):

If the route is filtered on R1 during the import phase, the route will not exist in R1’s routing table and thus cannot be advertised to either R2 or R3.

This fails to meet the requirement because the route must exist in R1's and R3's routing tables.

Option D (Filter-policy on R1 for filtering the imported routes to be advertised):

Filtering routes on R1 before advertising to R2 will prevent R2 from receiving the route but allow R1 to advertise the route to R3.

This meets the requirement.

Correct Option:

C (Filter-policy on R1 for filtering the routes to be imported): This will prevent the route from existing in both R1 and R3, violating the stated requirement.

Policy-Based Routing (PBR) on interfaces is used to forward traffic based on specific policies rather than the routing table. However, PBR is not suitable for modifying the next-hop of locally originated traffic. Other scenarios listed are typical use cases for interface PBR ​.

Option A is false. When advertising a route to an IBGP peer, the BGP speaker does not modify the AS_Path. It simply advertises the route as-is, preserving the AS_Path learned from EBGP.

Clarification of the options:

B is correct: When a route is sent to an EBGP peer, the local AS is prepended to the AS_Path.

C is correct: The AS_Path begins with the local AS when a new route is advertised to an EBGP neighbor.

D is correct: IBGP does not modify AS_Path when passing routes within the same AS.

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

“BGP speakers prepend their AS number to the AS_Path only when advertising to EBGP peers. IBGP peers do not alter the AS_Path.”

(Chapter: BGP Path Attributes – Section: AS_Path)

RPF (Reverse Path Forwarding) checks are used to prevent multicast loops. An RPF check uses the unicast routing table (or multicast static routes, if configured) to determine the correct incoming interface for a multicast packet.

Multicast protocols like PIM use the RPF mechanism, and the unicast routing table is the primary reference.

Multicast dynamic routing protocols do not maintain their own separate tables for RPF by default.

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

“RPF checks are performed using the unicast routing table or multicast static routes. The interface through which the multicast source is reachable is considered valid for RPF.”

(Chapter: Multicast – Section: RPF Principle)