Huawei H12-821 Exam Questions
HCIP-Datacom-Core Technology V1.0 (Page 4 )

Updated On: 12-Jun-2026

Preferences of routing protocols determine the sequence in which a router selects a route among routes to the same destination learned through different routing protocols.

  1. TRUE
  2. FALSE

Answer(s): A

Explanation:

The preference (or administrative distance) of a routing protocol determines the order in which a router selects routes when multiple routes to the same destination are learned through different routing protocols.
Each routing protocol is assigned a preference value, with lower values being more preferred. For example:
Direct routes have the lowest preference (most preferred).
Static routes often have a lower preference than dynamic routing protocols.
Among dynamic protocols, OSPF, BGP, and RIP have different preferences based on their design.

If a router learns multiple routes to the same destination from different protocols, it selects the route with the lowest preference value. This mechanism ensures proper route selection and efficient forwarding.



Which of the following attributes cannot be directly referenced in an apply clause of a route-policy?

  1. IP-prefix
  2. origin
  3. tag
  4. community

Answer(s): A

Explanation:

The apply clause in a route-policy is used to modify certain attributes of a route during route processing.
However, IP-prefix is not an attribute that can be directly modified in an apply clause because it is used as a matching condition in the if clause or as part of a filtering policy.



To filter traffic, you can use the traffic-filter or MQC. The MQC can be applied in more views than the traffic- filter.

  1. TRUE
  2. FALSE

Answer(s): A

Explanation:

Traffic-filter: This is a traditional method of filtering traffic using ACLs (Access Control Lists). It is limited in terms of flexibility and the views or contexts where it can be applied (e.g., interface-level filtering).
MQC (Modular Quality of Service Command-line): This is a more versatile framework that can classify, mark, police, and shape traffic. MQC can be applied in more views, including interface views, global views, and QoS policy views, making it more flexible and powerful than the traditional traffic-filter approach.



Which of the following route selection tools can be used by other routing protocols in addition to BGP?

  1. community-filter
  2. ACL
  3. IP-prefix
  4. as-path-filter

Answer(s): B,C

Explanation:

ACLs are generic tools used for filtering based on IP addresses, protocol types, and ports. They can be used in various scenarios across different routing protocols, not just BGP, making them a multipurpose tool.
IP-prefix lists are widely used for route filtering and selection across multiple routing protocols (e.g., OSPF, IS- IS, BGP). They provide a structured way to define IP address ranges.



The following is part of configuration on the router.
Which of the following statements regarding the configuration is true?

[HUAWEI]ip ip-prefix pl permit 10.0.192.0 8 greater-equal 17 less-equal 18

  1. In the 10.0.192.0/8 network segment, a route with a mask length of 18 matches the prefix list, and behavior for the matching routes is permit.
  2. In the 10.0.192.0/8 network segment, a route with a mask length of 20 matches the prefix list, and behavior for the matching routes is permit.
  3. In the 10.0.192.0/8 network segment, a route with a mask length of 19 matches the prefix list, and behavior for the matching routes is permit.
  4. In the 10.0.192.0/8 network segment, a route with a mask length of 21 matches the prefix list, and behavior for the matching routes is permit.

Answer(s): A

Explanation:

The prefix must be in the 10.0.192.0/8 network.
The prefix length (subnet mask) must be greater than or equal to 17 and less than or equal to 18.
The action for matching routes is permit.



The Rapid Spanning Tree Protocol (RSTP) defines four port roles. The Flags fields indicating the alternative and backup port roles in RST BPDUs are the same, that is, 01.

  1. TRUE
  2. FALSE

Answer(s): A

Explanation:

In Rapid Spanning Tree Protocol (RSTP), the Flags field in RST BPDUs is used to encode port roles and states. Both the alternative port and backup port roles are indicated with the same value, 01, in the Flags field of RST BPDUs. This is because:
Alternative Port: A port that provides an alternate path to the root bridge but is blocked to prevent loops.
Backup Port: A port that provides a redundant path to the same segment as another designated port but is also blocked.
Since both roles involve blocking the port to prevent loops, they are encoded similarly in the RST BPDU Flags field. Thus, the statement is true.



FILL BLANK

When configuring an IPv4 multicast routing protocol, you need to run the `____________ routing-enable' command first, and then perform PIM-related configurations. (Enter the full command in lower case. Command abbreviation is prohibited.)

  1. multicast

Answer(s): A

Explanation:

The multicast routing-enable command is required because it enables multicast routing functionality on the device. Without this command, the device cannot process or forward multicast traffic, as multicast routing is disabled by default on most network devices for performance and security reasons.

1. Global Multicast Routing Activation:
The multicast routing-enable command globally activates multicast routing on the device. It is a prerequisite for any multicast protocol configuration (e.g., PIM, IGMP).

2. Dependency for Protocol Configuration:
Protocol Independent Multicast (PIM) and other multicast protocols rely on the multicast routing engine to operate. Without enabling multicast routing, the router will not be able to process PIM join/prune messages, manage multicast group memberships, or build multicast distribution trees.

3. Foundation for Multicast Forwarding:
Multicast routing requires specific mechanisms like Reverse Path Forwarding (RPF) checks and multicast forwarding tables. These mechanisms are initialized only after the multicast routing-enable command is issued.



A source tree is the shortest path from a multicast source to receiver hosts, it is also called a shortest path tree (SPT).

  1. TRUE
  2. FALSE

Answer(s): A

Explanation:

A source tree, also known as a shortest path tree (SPT), is indeed the shortest path from a multicast source to receiver hosts. This type of tree is built with the source at the root and branches extending to all multicast receivers.
Characteristics of a Source Tree (SPT):
Each branch represents the optimal path between the source and a receiver.

It is constructed using unicast routing information to determine the shortest path.

In multicast routing protocols like PIM-SM (Protocol Independent Multicast Sparse Mode), an SPT is often built when switching from a shared tree to a source-specific tree for more efficient delivery.



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