Free H12-821_V1.0 Exam Braindumps (page: 9)

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ACLs are a common matching tool in routing policies. An ACL can be configured on a router to match routes.

  1. TRUE
  2. FALSE

Answer(s): A

Explanation:

ACL in Routing Policies

ACLs are frequently used in routing policies to match specific routes based on criteria such as source

IP, destination IP, and more. This allows ACLs to influence route redistribution, filtering, and forwarding decisions.

HCIP-Datacom-Core Reference

ACL applications in routing policies are discussed in the routing policy chapters.



Both MQC and PBR can be applied on device interfaces to filter received and sent packets or control packet forwarding paths.

  1. TRUE
  2. FALSE

Answer(s): A

Explanation:

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.



An IP prefix list is a common matching tool used in routing policies.
Which of the following cannot be configured as matching conditions in an IP prefix list on a Huawei router?

  1. Port number
  2. Mask
  3. Action
  4. Index

Answer(s): A

Explanation:

IP Prefix List Matching Conditions

An IP prefix list matches based on:

Mask: Specifies the subnet mask length.

Action: Specifies whether to permit or deny.

Index: Orders the rules within the prefix list.

Port numbers are not applicable as matching conditions in an IP prefix list.

HCIP-Datacom-Core Reference

IP prefix list configurations are detailed in the routing policy and route filtering chapters.



When receiving a packet, a Huawei router matches the packet against ACL rules. The default ACL matching order used by the Huawei router is:

  1. Randomly selects a rule to match the packet
  2. Matches the rules in reverse order (from bottom to top)
  3. Matches the rules sequentially (from top to bottom)
  4. Compares all rules and selects the best match

Answer(s): C

Explanation:

Huawei routers process Access Control List (ACL) rules sequentially, meaning they check each rule one by one, from top to bottom, in the order they were configured. The first rule that matches the packet determines the action (permit or deny), and no further rules are evaluated. If no rule matches, the packet is denied by default due to the implicit deny rule at the end of the ACL.


Reference:

HCIP-Datacom-Core Technology Training Material (ACL Principles and Configuration).

Sequential Matching Order:

By default, Huawei routers match packets against ACL rules sequentially. This means:

The router checks the packet against rules in the order they are listed, starting from the top of the ACL.

The first rule that matches the packet's attributes is applied, and no further rules are checked. This is known as the first-match principle.

If no rules match, the packet is denied by default (implicit deny).


HCIP-Datacom Advanced Routing & Switching Technology (ACL Matching Mechanism).

Example of Sequential Matching:

Consider the following ACL rules:

Rule 10: Permit IP 192.168.1.0/24

Rule 20: Deny IP 192.168.1.1

If a packet with source IP 192.168.1.1 arrives:

The router matches it against Rule 10 (Permit 192.168.1.0/24) and allows the packet.

Rule 20 is not evaluated because the first match (Rule 10) already applies.

Alternative Matching Orders:

Some routers or configurations allow batch matching (evaluating all rules) for specific scenarios, but this is not the default behavior in Huawei routers.

Conclusion:

The default ACL matching order on Huawei routers is sequential, and the first matching rule determines the action applied to the packet.






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