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Cisco Quality of Service (QoS) Sample Questions:

1. According to the best practices, in a service provider network, which statement is true as related to the QoS policy that should be implemented on the inbound provider (P) to provider (P) router link?

A) Traffic policing should be implemented to rate-limit the ingress traffic into the P router.
B) Class-based marking should be implemented because it will be needed for the class-based queuing that will be used on the P router output.
C) In the DiffServ model, all ingress and egress QoS processing are done at the network edge (for example, PE router), so no input or output QoS policy will be needed on the P to P link.
D) Because traffic should have already been policed and marked on the upstream ingress PE router, no input QoS policy is needed on the P to P link.

2. Based on the configuration, which two statements are true? (Choose two.)
Policy-map shape-cbwfq
Class interactive
Shape average 256000
Shape adaptive 128000
Bandwidth 128

A) The interactive traffic class will have a min-rate (min-cir) of 128 kbps.
B) If the interactive traffic class exceeds an average rate of 256 kbps, the traffic rate will be throttled down to 128 kbps.
C) This configuration allows class-based traffic shaping to lower the traffic rate in response to the BECN bit.
D) The interactive traffic class will have a minimum bandwidth guarantee of 256 kbps.
E) The interactive traffic class will have a maximum bandwidth guarantee of 256 kbps.

3. What is the purpose of the qos pre-classify command?

A) to enable the IOS to classify the packet based on the original IP header instead of the tunnel IP header
B) to enable the IOS to copy the ToS field from the outer tunnel IP header back into the original IP header
C) to enable class-based marking on IPSec crypto maps
D) to enable the IOS to classify the packet based on the outer tunnel IP header instead of the original IP header
E) to enable class-based marking on tunnel interface
F) to enable the IOS to copy the ToS field from the original IP header to the outer tunnel IP header

4. Which three characteristics are drawbacks to the use of a best-effort with over-provisioning backbone design? (Choose three.)

A) The design uses a different over-provisioning ratio for the different traffic classes.
B) It requires complex QoS mechanisms at the network core.
C) Unplanned network failures can cause unexpected congestion in the network.
D) It requires complex QoS mechanisms at the network edge.
E) The design costs more to implement than a DiffServ backbone.
F) Denial of Service attacks on one service can affect all network traffic.

5. The following commands have been configured under the fa0/1 interface on the 2950 switch:
wrr-queue bandwidth 20 1 80 0
mls qos trust cos
mls qos trust device cisco-phone
Voice traffic from the IP phone that is directly connected to the fa0/1 interface is experiencing excessive delays. What could be the cause of this problem?

A) The default cos-to-dscp map is being used.
B) The default dscp-to-cos map is being used.
C) The default wrr-queue cos-map is being used.
D) The trust boundary configuration is not correct.
E) The wrr-queue bandwidth weightings are not correct.

Solutions: