CCNP Voice FAQ: Implementing QoS Pre-Classify and Deploying End-to-End QoS

CCNP Voice FAQ: Implementing QoS Pre-Classify and Deploying End-to-End QoS

Q1. Which of the following is not a critical function of VPNs?
A. Confidentiality
B. Data integrity
C. Authentication
D. Accounting

Answer: D

Q2. Which of the following is not a VPN type?
A. Client-initiated remote access
B. Internet
C. NAS-initiated remote access
D. Intranet

Answer: B

Q3. Which type of interface is QoS pre-classify for?
A. Tunnel interface
B. Loopback interface
C. VRF interface
D. Logical interface

Answer: A

Q4. Which of these QoS pre-classify deployment options is invalid?
A. Apply the policy to the tunnel interface without QoS pre-classify when you want to classify packets based on the pre-tunnel header.

B. Apply the policy to the physical interface without QoS pre-classify when you want to classify packets based on the post-tunnel header.

C. Apply the policy to the tunnel interface without QoS pre-classify when you want to classify packets based on the post-tunnel header.

D. Apply the policy to the physical interface and enable QoS pre-classify when you want to classify packets based on the pre-tunnel header.

Answer: C

Q5. Which of the following Cisco IOS commands enables QoS pre-classify on an interface?
A. qos classify
B. preclassify
C. preclassify qos
D. qos pre-classify

Answer: D

Q6. Which of the following is not a typical IP QoS SLA parameter?
A. Delay
B. Jitter
C. CLP
D. Loss

Answer: C

Q7. Which of the following is an invalid campus QoS guideline?
A. Mark traffic at the distribution layer device.
B. Use multiple queues on the transmit interfaces.
C. Perform QoS in hardware when possible.
D. Police unwanted traffic as close to the source as possible.

Answer: A

Q8. Which of the following is not a Cisco router functional plane?
A. Data plane
B. Process plane
C. Management plane
D. Control plane

Answer: B

Q9. Which of the following is not a CoPP deployment step?
A. Define a packet classification criteria.
B. Define a service policy.
C. Enter global configuration mode and apply a QoS policy.
D. Enter control plane configuration mode and apply QoS policy.

Answer: C

Q10. Which of the following is not a typical customer edge-to-provider edge WAN link required QoS feature?
A. Queuing
B. Shaping
C. LFI or cRTP
D. CoPP

Answer: D

Q11. Provide a definition for VPN.

Answer: A VPN provides private network connectivity over a public/shared infrastructure. The same policies and security as a private network are offered using encryption, data integrity, and origin authentication.

Q12. What types of interfaces is QoS pre-classify designed for?

Answer: QoS pre-classify is designed for tunnel interfaces such as GRE and IPsec.

Q13. What Cisco IOS command enables QoS pre-classify on an interface?

Answer: qos pre-classify enables QoS pre-classify on an interface.

Q14. What are the QoS pre-classification deployment options?

Answer: You can apply a QoS service policy to the physical interface or the tunnel interface. Applying a service policy to a physical interface causes that policy to affect all tunnel interfaces on that physical interface. Applying a service policy to a tunnel interface affects that particular tunnel only and does not affect other tunnel interfaces on the same physical interface. When you apply a QoS service policy to a physical interface where one or more tunnels emanate, the service policy classifies IP packets based on the post-tunnel IP header fields. However, when you apply a QoS service policy to a tunnel interface, the service policy performs classification on the pre-tunnel IP packet (inner packet).

Q15. Provide a definition for QoS SLA.

Answer: The QoS SLA provides contractual assurance for parameters such as availability, throughput,
delay, jitter, and packet loss.

Q16. What are the typical maximum end-to-end (one-way) QoS SLA requirements (delay, jitter, loss) for voice?

Answer: The typical maximum end-to-end (one-way) QoS SLA requirements for voice delay <= 150 ms, jitter <= 30 ms, and loss <= 1 percent.

Q17. Provide at least two of the guidelines for implementing QoS in campus networks.

Answer: The guidelines for implementing QoS in campus networks are as follows:

  • Classify and mark traffic as close to the source as possible.
  • Police traffic as close to the source as possible.
  • Establish proper trust boundaries.
  • Classify and mark real-time voice and video as high-priority traffic.
  • Use multiple queues on transmit interfaces.
  • When possible, perform hardware-based rather than software-based QoS.

Q18. Provide at least two QoS policies to be implemented on campus network access or distributed switches.

Answer: In campus networks, access switches require these QoS policies:

  • Appropriate trust, classification, and marking policies
  • Policing and markdown policies
  • Queuing policies

The distribution switches, on the other hand, need the following:

  • DSCP trust policies
  • Queuing policies
  • Optional per-user micro-flow policies (if supported)

Q19. Provide a definition for CoPP.

Answer: Control plane policing (CoPP) is a Cisco IOS feature that allows you to configure a quality of service (QoS) filter that manages the traffic flow of control plane packets. Using CoPP, you can protect the control plane of Cisco IOS routers and switches against denial of service (DoS) and reconnaissance attacks and ensure network stability (router/switch stability in particular) during an attack.

Q20. How is CoPP deployed?

Answer: The four steps required to deploy CoPP (using MQC) are as follows:
Step 1 Define a packet classification criteria.
Step 2 Define a service policy.
Step 3 Enter control plane configuration mode.
Step 4 Apply a QoS policy.

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