Ensurepass

QUESTION 41

Refer to the exhibit. Which configuration error prevents this traffic-shaping policy from working?

 

clip_image002

 

A.

The WAN interface is starting to drop packets because no queuing mechanism is implemented.

B.

Traffic-shaping policies are applied only in the outbound direction.

C.

The class_A configuration shape peak is used to maximize the serial interface performances.

D.

The service-policy command is applied only on logical or channeled interfaces.

 

Correct Answer: B

 

 

QUESTION 42

What is an important requirement with MPLS applications like Layer 3 MPLS VPNs?

 

A.

All the PE routers loopback addresses should be summarized to reduce the number of routing table entries in the core routers.

B.

Targeted hellos are required between all the PE routers.

C.

An end-to-end LSP is required between the PE routers.

D.

The LSPs that are built between the PE routers must be symmetrical (bidirectional).

 

Correct Answer: C

 

 

QUESTION 43

Which two features are used to provide Cisco MPLS TE node and link protection? (Choose two.)

 

A.

autoroute

B.

fast reroute

C.

backup tunnels

D.

BFD

 

Correct Answer: BC

 

 

QUESTION 44

What is the correct formula for determining the CIR?

 

A.

CIR = Bc/Tc

B.

CIR = Bc x Tc

C.

CIR = Tc/Bc

D.

CIR = Bc + Be

E.

CIR = Tc/(Bc+Be)

F.

CIR = (Bc+Be)/Tc

 

Correct Answer: A

Explanation:

Committed Information Rate (CIR) – the rate the device will send at (on average) over a one second period.

The default CIR when traffic-shaping is enabled on the interface is 56K. CIR is also referred to as the “target rate”. Since the device is forced to send at the AR, it does not send all of the time (within one second) – in order to send an average amount of data that equals the CIR.

Minimum CIR (mincir) – the rate the service provider guarantees to accept. Theoretically, the provider will set the DE bit for all traffic above this rate. Mincir is designed to be used in conjunction with adaptive shaping. With adaptive shaping, the router will throttle down in the event of congestion. The router will not throttle down below this value.

Committed Burst (Bc) – the number of committed bits allows to be sent during a given interval. The device sends an average amount of traffic to achieve the CIR. The Bc value defaults to 1/8 of the configured CIR for speeds below 650K. For speeds above that, it is roughly 1/16 of CIR.

Excess Burst (Be) – the number of non-committed bits the router is allowed to send above Bc during the first interval (Tc). The amount of Be “credits” is derived from unused Bc credits in previous intervals. There is no limit to how long Be can “store” unused Bc credits. It is a common misconception that Be can only store credits from the previous interval or the previous second. There is no default Be value.

 

Committed Rate Measurement Interval (Tc) – the time interval over whic Bc or Bc+Be can be transmitted. The max value is 125 ms and the minimum value is 10 ms.

 

The Formula

CIR, Tc, and Bc are related mathematically by the following formula:

CIR = Bc/(Tc/1000) Notice the division of Tc by 1000 is used to convert milliseconds into seconds – the common measurement of CIR and Bc.

QUESTION 45

Which two network devices are trusted endpoints in a network? (Choose two.)

 

A.

video endpoint

B.

PC

C.

wireless clients

D.

IP phone

 

Correct Answer: AD

 

 

QUESTION 46

Which item is not available to be used for QoS classification in Cisco IOS XR?

 

A.

MAC SA

B.

protocol

C.

inner EXP

D.

discard-class

E.

QoS-group

F.

VLAN

 

Correct Answer: C

 

 

QUESTION 47

Which option is a Cisco-recommended congestion management or queuing method for real-time traffic for voice and video?

 

A.

CB-WFQ

B.

PQ

C.

WFQ

D.

LLQ

 

Correct Answer: D

 

 

QUESTION 48

On a Cisco IOS XR router, which mechanism protects the router resources by filtering and policing the packets flows that are destined to the router that is based on defined flow-type rates?

 

A.

LLQ

B.

LPTS

C.

Committed Access Rate

D.

Control Plane Policing

E.

Management Plane Protection

F.

NetFlow

G.

ACL

 

Correct Answer: B

Explanation:

Local Packet Transport Services (LPTS) maintains tables describing all packet flows destined for the secure domain router (SDR), making sure t
hat packets are delivered to their intended destinations.

The Low Latency Queueing feature brings strict priority queueing to Class-Based Weighted Fair Queueing (CBWFQ).

 

 

QUESTION 49

Which statement is correct regarding the default MPLS TTL behavior?

 

A.

When an ingress edge LSR receives an IP packet, it will decrement the IP TTL field by 1; then it will set the MPLS Label TTL field to 255.

B.

When an ingress edge LSR receives an IP packet, it will decrement the IP TTL field by 1; then it will copy the decremented IP TTL field into the MPLS Label TTL field.

C.

When an ingress edge LSR receives an IP packet, it will just copy the IP TTL field into the MPLS Label TTL field.

D.

When an ingress edge LSR receives an IP packet, it will copy the IP TTL field into the MPLS Label TTL field first; then it will only decrement the MPLS Label TTL field by 1.

E.

When an ingress edge LSR receives an IP packet, it will copy the IP TTL field into the MPLS Label TTL field first; then it will only decrement the IP TTL field by 1.

 

Correct Answer: B

 

 

QUESTION 50

On Cisco routers, which QoS marker is only locally significant?

 

A.

DSCP

B.

MPLS EXP

C.

IP precedence

D.

QoS group

E.

discard eligible (DE)

 

Correct Answer: D

 

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