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350-501 · Question #369

Refer to the exhibit A user is performing QoS marking on internet traffic and sending it with IPv4 and IPv6 headers on the provider edge device PE1. IPv4 traffic is classified with DSCP 4 and IPv6…

The correct answer is A. Create an access list that includes any IPv6 traffic and apply it to CM-20. To begin implementing QoS for IPv6 traffic on PE1, which is intended to be classified with DSCP 6, the engineer must first create an IPv6 access list to identify the target traffic and then integrate it into the appropriate class-map like CM-20.

Networking

Question

Refer to the exhibit A user is performing QoS marking on internet traffic and sending it with IPv4 and IPv6 headers on the provider edge device PE1. IPv4 traffic is classified with DSCP 4 and IPv6 traffic is classified with DSCP 6. Which action must the engineer take to begin implementing a QoS configuration on PE1 for the IPv6 traffic?

Exhibit

350-501 question #369 exhibit

Options

  • ACreate an access list that includes any IPv6 traffic and apply it to CM-20.
  • BCreate access list IPv6-match and configure match ip dscp 4 and match ip dscp 6 in class maps
  • CConfigure match ip dscp 4 in class map CM-10 and match ip dscp 6 in class map CM-20.
  • DCreate access list IPv6-filter and remove DSCP value 4 and 6 in class maps CM-10 and CM-20.

How the community answered

(33 responses)
  • A
    82% (27)
  • B
    3% (1)
  • C
    12% (4)
  • D
    3% (1)

Why each option

To begin implementing QoS for IPv6 traffic on PE1, which is intended to be classified with DSCP 6, the engineer must first create an IPv6 access list to identify the target traffic and then integrate it into the appropriate class-map like CM-20.

ACreate an access list that includes any IPv6 traffic and apply it to CM-20.Correct

The existing 'match ip dscp 6' in class-map CM-20 only applies to IPv4 traffic. To correctly classify IPv6 traffic, which should also be associated with DSCP 6, a specific IPv6 matching mechanism is required. Creating an IPv6 access list and then matching it within class-map CM-20 using 'match ipv6 access-group' allows the engineer to begin identifying and processing IPv6 traffic.

BCreate access list IPv6-match and configure match ip dscp 4 and match ip dscp 6 in class maps

Configuring 'match ip dscp' in class maps is incorrect for IPv6 traffic, as 'match ip dscp' specifically applies to IPv4 headers.

CConfigure match ip dscp 4 in class map CM-10 and match ip dscp 6 in class map CM-20.

This option suggests configuring 'match ip dscp 4' and 'match ip dscp 6' in class maps, which is essentially the configuration already shown in the exhibit and incorrect for matching IPv6 traffic.

DCreate access list IPv6-filter and remove DSCP value 4 and 6 in class maps CM-10 and CM-20.

Removing DSCP values from class maps does not implement QoS for IPv6; instead, it would remove existing classification criteria.

Concept tested: QoS classification for IPv6 traffic

Source: https://www.cisco.com/c/en/us/td/docs/ios/qos/configuration/guide/12_4t/qos_c1/qcqosipv6.html

Topics

#QoS#IPv6#Traffic Classification#Access Control Lists

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