642-887 Real Exam (March 2016)

[Free] Download Latest (March 2016) Cisco 642-887 Real Exam 71-80

March 5, 2016

Ensurepass

QUESTION 71

On the Cisco ASR9K router, when using the bandwidth command to specify the minimum guaranteed bandwidth to be allocated for a specific class of traffic, what will be used as the queuing algorithm?

 

A.

custom queuing

B.

CBWFQ

C.

WFQ

D.

FIFO

E.

priority queuing

 

Correct Answer: B

Explanation:

Class based weighted fair queuing (CB-WFQ) was initially released without the support of a priority queuing system, thus it could not guarantee the delay and jitter (delay variation) requirements of real-time, interactive voice and video conversations. Since for CBWFQ, the weight for a packet belonging to a specific class is derived from the bandwidth assigned to the class, which in turn determines the order in which packets are sent. All packets are serviced fairly based on weight and no class of packets may be granted strict priority. This scheme poses problems for voice traffic that is largely intolerant of delay, especially variation in delay

 

 

QUESTION 72

You are tasked to enable LDP on many of the interfaces on the Cisco CRS-3 router, and because there are many interfaces that need to have LDP enabled, you mistakenly did not enable LDP on all the required interfaces. To prevent this issue from happening again in the future, what could you do the next time you need to enable LDP on many interfaces?

 

A.

use the mpls ldp auto-config command under the IGP routing process

B.

use the mpls ldp sync command under the IGP routing process

C.

use the interface all command under the MPLS LDP process

D.

use the discovery command under the MPLS LDP process

 

Correct Answer: A

 

 

 

 

 

 

QUESTION 73

The network architecture team is proposing to enable Cisco MPLS TE over the entire service provider core network. Which two options are benefits of Cisco MPLS TE that affect their decision? (Choose two.)

 

A.

Cisco MPLS TE optimizes network resources.

B.

Cisco MPLS TE data flows independent from the underlying IGP.

C.

Cisco MPLS TE increases the data forwarding rate.

D.

Cisco MPLS TE tunneling does not require maintenance.

E.

Cisco MPLS TE offers network resource reservation, which removes any need for QoS MQC policies.

 

Correct Answer: AB

 

 

QUESTION 74

When implementing MPLS TE tunnels on Cisco IOS XR routers, what is the tunnel setup and hold priority value range, and which value has the highest priority?

 

A.

0-63, where 0 is the highest priority

B.

0-63, where 63 is the highest priority

C.

0-7, where 0 is the highest priority

D.

0-7, where 7 is the highest priority

 

Correct Answer: C

 

 

QUESTION 75

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?

 

A.

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

B.

the maximum threshold

C.

the minimum threshold

D.

the mark probability denominator

 

Correct Answer: D

Explanation:

Comparison of Cisco IOS QoS and Cisco IOS-XR QoS

The Cisco IOS-XR software implementation of QoS is basically the same as the QoS implementation on Cisco

IOS software, with the following exceptions:

On Cisco IOS-XR software, the bandwidth command can be configured only in egress policies.

The following changes have been made to the class-map command on Cisco IOS-XR software:

Supports 4K per logical router.

Maximum number of match criteria configurable in one class map is eight.

When a class is marked as high priority using the priority command on Cisco IOS-XR software, we recommend that you configure a policer to limit the priority traffic. Limiting the priority traffic will ensure that the priority traffic does not starve all of the other traffic on the line card. Use the police command to explicitly configure the policer.

On Cisco IO-XR software, only one conform-action, exceed-action, or violate-action command can be configured at a time. To configure traffic policing, use the police command.

On Cisco IOS-XR software, policy modifications cannot be made on existing policies. Use the policy-map command to remove the policy from all attached interfaces, delete the policy map, and redefine a new policy.

When configuring a policy map on Cisco IOS-XR software, the maximum number of classes configurable in one policy map is 16, which includes both Level 1 and Level 2 classes. To configure a policy map, use the policy-map command.

When WRED is configured on Cisco IOS-XR software, the mark probability in the random- detect command is not configurable–it is always set to 1.

When the random-detect exp command is used on Cisco IOS-XR software, the exponential weighting constant is not configurable and will be programmed automatically by Cisco IOS-XR software.

When access control lists (ACLs) are used in QoS class maps, the underlying deny or permit actions associated with access control entries (ACEs) are ignored. ACEs are used as a classification mechanism in order to provide appropriate QoS behavior as specified in class maps. Use ACLs that include ACEs with permit actions only.

 

 

QUESTION 76

An engineer is working in a service provider environment to troubleshoot a MPLS VPN. The engineer determines that LDP neighborship is flapping between two routers and causing disruption to the traffic. Which LDP feature can help to solve the issue?

 

A.

LDP Discovery

B.

LDP auto-configuration

C.

LDP graceful-restart

D.

LDP NSF

 

Correct Answer: C

 

 

QUESTION 77

In Cisco MPLS TE implementations, what can cause the tunnel bandwidth to adjust automatically based on the traffic load in the tunnel?

 

A.

fast reroute

B.

admin weight

C.

autobandwidth

D.

bandwidth subpool

 

Correct Answer: C

 

 

QUESTION 78

On Cisco routers, which three methods can be used to map traffic into the MPLS traffic engineering tunnel? (Choose three.)

 

A.

on-demand routing

B.

static routing

C.

optimized edge routing

D.

policy-based routing

E.

autoroute

 

Correct Answer: BDE

 

 

 

QUESTION 79

A network engineer must make a reservable maximum bandwidth of 75 Mbps on a Cisco ASR 9000 series router. Which configuration satisfies this requirement in Cisco IOS XR?

 

A.

2802_FY14Q4_CORE_Q33_o1

B.

2813_FY14Q4_CORE_Q33_o2

C.

2824_FY14Q4_CORE_Q33_o3

D.

2835_FY14Q4_CORE_Q33_o4

 

Correct Answer: C

 

 

QUESTION 80

How many labels does an MPLS packet have, with a bottom-of-stack label set to zero?

 

A.

The packet has no label.

B.

The packet has one label.

C.

The packet may have one or more labels.

D.

The packet has at least two labels.

 

Correct Answer: D

 

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