300-420 Question 250
Select 3An enterprise network administrator is tasked with ensuring that voice traffic is prioritized over other types of traffic in the network. To achieve this, the administrator plans to implement classification and marking using DSCP (Differentiated Services Code Point) values. Which of the following actions should the administrator take to correctly classify and mark voice traffic for prioritization?
- A
Use a class map to identify traffic based on Layer 7 application signatures.
- B
Mark voice traffic with DSCP value EF (Expedited Forwarding).
- C
Configure a policy map to apply DSCP markings to identified traffic.
- D
Use a network-based ACL to block non-voice traffic during congestion.
- E
Apply the policy map to the appropriate interface using a service policy.
Show answer and explanation
Correct answers: B, C, E
Explanation
To prioritize voice traffic, the administrator must classify and mark the traffic correctly. DSCP EF (Expedited Forwarding) is the industry standard for marking voice traffic due to its low latency and high-priority treatment. A policy map is used to apply this marking, and the service policy attaches this configuration to an interface. Together, these ensure that voice traffic is classified, marked, and prioritized as it traverses the network.
- A. Incorrect.
Layer 7 application signatures are typically used in advanced application-based traffic classification, but they are not required for simple DSCP classification and marking.
- B. Correct.
DSCP EF (Expedited Forwarding) is the standard marking for voice traffic as it provides low latency and high priority treatment in the network.
- C. Correct.
A policy map is used to apply DSCP markings based on classified traffic, ensuring that the traffic is treated appropriately by downstream devices.
- D. Incorrect.
Blocking non-voice traffic during congestion is not a classification or marking action. It is more related to traffic policing or shaping, which is a different QoS mechanism.
- E. Correct.
Service policies are used to apply policy maps to interfaces, enabling the marking and classification of traffic at the network edge where it enters the network.