Cisco 642-887 Exam Questions

Question 6 of 179

On Cisco routers, how is hierarchical QoS implemented?

Within the parent policy, reference another child policy using the policy-map command.

Within the child policy, reference another parent policy using the policy-map command.

Use the policy-map command within a service-policy to implement nested policy-maps.

Within the parent policy-map, reference another child policy-map using the service-policy command.

Correct Answer: D

Question 7 of 179

Refer to the Cisco IOS XR policy-map configuration exhibit.
Exam 642-887: Question 7 - Image 1

What is wrong with the policy-map configuration?

missing the priority percent command under class one and class two

missing the police command under class one and class two

missing the police command under class three

missing the priority bandwidth command under class one and class two

missing the bandwidth command under class one and class two

Correct Answer: B

Question 8 of 179

When configuring class-based WRED on Cisco routers, which WRED parameter is not user configurable on a Cisco IOS XR but is user configurable on a Cisco
IOS and IOS XE?

the ingress or egress direction where the class-based WRED policy will be applied

the maximum threshold

the minimum threshold

the mark probability denominator

Correct Answer: D

Question 9 of 179

Which of the following three statements are correct regarding IPv6 QoS? (Choose three.)

The traffic class field in the IPv6 header can be used to set specific precedence or DSCP values.

A 20-bit flow label field enables per-flow processing.

DS-TE is not supported by IPv6.

Per-hop behavior in IPv6 networks is based on EXP bits.

IPv6 QoS features are configured using the modular QoS CLI on Cisco routers.

Correct Answer: A, B, E

http://www.cisco.com/en/US/technologies/tk648/tk872/technologies_white_paper0900aecd8026004d.pdf
Cisco Systems. IPv6 QoS

AT-A-GLANCE -

RFC 2460/3697 -
Currently IPv6 provides support for QoS marking via a field in the IPv6 header.
Similar to the type of service (ToS) field in the IPv4 header, the traffic class field (8 bits) is available for use by originating nodes and for forwarding routers to identify and distinguish between different classes or priorities of IPv6 packets.
Exam 642-887: Question 9 - Image 1

Current Cisco IOS Software support for IPv6 QoS includes:
✑ Packet classification
✑ Queuing (includes LLQ; excludes legacy PQ/CQ)
✑ Traffic shaping
✑ WRED
IPv6 also has a 20-bit field known as the flow label field (RFC 3697). The flow label enables per flow processing for differentiation at the IP layer.
It can be used for special sender requests and is set by the source node.
The flow label must be modified by an intermediate mode.
Planned Cisco IOS Software support for IPv6 QoS includes:
✑ Compressed Real-Time Protocol (cRTP)
✑ Network-based application recognition (NBAR)
Committed access rate (CAR)

ABE

Question 10 of 179

With unmanaged CE routers, at which point in the service provider network is the QoS trust boundary, and what is required at the trust boundary?

between the CE and PE router and mapping of the customer traffic classes into the service provider traffic classes at the PE router ingress

between the CE and PE router and trusting the QoS markings from the CE router and applying the required QoS mechanisms based on the customer QoS markings

between the PE and the P router and mapping of the customer traffic classes into the service provider traffic classes at the P router ingress

between the PE and P router and trusting the QoS markings from the CE router and applying the required QoS mechanisms based on the customer QoS markings

between the customer network and the CE router ingress and applying the required egress QoS policy on the CE router

Correct Answer: A