[Free] Download Latest (March 2016) Cisco 642-887 Real Exam 11-20

Ensurepass

QUESTION 11

Only based on the Cisco IOS XR policy-map configuration exhibit, which statement is correct?

 

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A.

All DSCP AF41 marked packets will be dropped when the average queue length reaches 12,000 packets.

B.

DSCP AF11 marked packets will be randomly dropped when the average queue length reaches 10,000 packets.

C.

DSCP AF11 and AF41 marked packets are guaranteed a minimum bandwidth of 1 Mb/s.

D.

DSCP AF11 and AF41 marked packets are guaranteed a maximum bandwidth of 1 Mb/s.

 

Correct Answer: B

 

 

QUESTION 12

Which statement describes the QoS behavior between P and PE routers of an MPLS provider network for an L3VPN service?

 

A.

The PE function honors DSCP markings set by the CE.

B.

The customer and provider must agree on DSCP classification and traffic priorities.

C.

Classification of customer traffic is handled by the P router.

D.

The PE function cannot map DSCP markings to MPLS EXP bits.

 

Correct Answer: B

 

 

QUESTION 13

DRAG DROP

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Correct Answer:

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QUESTION 14

According to the Intserv model, which two options are traffic-specific parameters? (Choose two.)

 

A.

token bucket

B.

calculated average queue size

C.

minimum policed unit< /font>

D.

traffic marking

E.

rate policing

 

Correct Answer: AC

 

 

QUESTION 15

When implementing CBWFQ, where should Weighted Random Early Detection configuration be applied?

 

A.

route-map

B.

policy-map

C.

class-map

D.

service-policy

 

Correct Answer: B

 

 

QUESTION 16

Which four pieces of information are stored for each prefix in the LFIB? (Choose four.)

 

A.

local label

B.

outgoing label

C.

next-hop IP address

D.

outgoing interface

E.

incoming interface

F.

Layer 2 header rewrite information

 

Correct Answer: ABCD

Explanation:

Forwarding Labeled Packets

LSR forwards the packet based on:

Top Label value of the received packet

Corresponding entry in LFIB (LABEL <=> INTERFACE)

#show mpls forwarding-table – will show:

local label

outgoing label

prefix (network)

outgoing interface

next-hop

 

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LSR expects packet to come with “top” label being “Local” (from show mpls forwarding- table).

If Outgoing label is “Aggregate”, then that means that this is a summary route and more specific lookup is performed.

If LSR cannot find label/interface mapping in LFIB, then it drops the packet. There are several “RESERVED” labels numbered from 0 to 15:

0 – explicit NULL – is used to preserver QoS info through EXP bits. It copies ‘ip prec’ or DiffServ.

1 – Router alert label – forces LSR to software switch the packet.

3 – Implicit NULL – this label is used for “connected” or “summary” routes. This way LSR signals its neighbors to execute “POP label” operation on “connected” routes. It is called PHP, Penultimate Hop Popping, and is used to make sure that LSR does not perform 2 lookups (label + ip).

14 – OEM alert label – is used for monitoring purpose.

In Cisco IOS, the default range is 16 through 100,000, but can be expanded by using “mpls label range” command.

 

 

QUESTION 17

Which Cisco IOS XR command should be used in order to enable LDP on all interfaces for which the IGP protocol is enabled?

 

A.

RP/0/0/CPU0:R1(config-ospf)#mpls ldp auto-config

B.

RP/0/0/CPU0:R1(config-ospf)#mpls ldp interface all enable

C.

RP/0/0/CPU0:R1(config-ospf)#enable all

D.

RP/0/0/CPU0:R1(config-ldp)#enable all

 

Correct Answer: A

 

 

 

 

 

 

 

 

 

QUESTION 18

Refer to the Cisco IOS XR configuration exhibit. Which statement is correct?

 

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A.

The backup tunnel-te 10 tunnel is using the highest setup and hold priority settings of 7.

B.

The backup tunnel path is learned dynamically.

C.

The fast-reroute command is missing under the (config-mpls-te-if)# configuration mode.

D.

Interface gi0/0/0/10 is the protected link.

 

Correct Answer: D

 

 

QUESTION 19

LDP session protection uses which one to maintain the LDP session between LDP neighbors?

 

A.

LDP NSF

B.

LDP NSR

C.

backup-targeted LDP hellos

D.

BFD

E.

LDP-IGP synchronization

 

Correct Answer: C

 

 

QUESTION 20

Which QoS technique can be used to protect customer traffic from being dropped by traffic rate limiting performed by the service provider?

 

A.

LLQ

B.

policing

C.

fair-queue

D.

shaping

 

Correct Answer: D

 

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