Cisco 642-887 Vce 2021

NEW QUESTION 1
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?

• A. between the CE and PE router and mapping of the customer traffic classes into the service provider traffic classes at the PE router ingress
• B. 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
• C. 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
• D. 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
• E. between the customer network and the CE router ingress and applying the required egress QoS policy on the CE router

Answer: A

NEW QUESTION 2
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

Answer: C

NEW QUESTION 3
Which method is used to mark traffic matched by class-map MY_CLASS as Expedited Forwarding?

• A. set ip dscp cs7
• B. set dscp cs7
• C. set dscp 46
• D. set dscp 45

Answer: C

NEW QUESTION 4
Which affinity value will be matched by the affinity bit mask of the affinity 0xFF00000A mask 0xFFFF000F command?

• A. 0xFFFF000A
• B. 0xFF00EEEA
• C. 0xFF000000
• D. 0x00000000
• E. 0x11110001

Answer: B

Explanation:
0xFF00000A 11111111000000000000000000001010
0xFFFF000F 11111111111111110000000000001111
0xFF00EEEA 11111111000000001110111011101010

NEW QUESTION 5
Which class-map configuration selects the following traffic?
All incoming traffic from interface GigabitEthernet 0/1 that is marked with dscp ef
A)

B)

C)

D)

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Answer: A

NEW QUESTION 6
You are configuring MPLS LDP in a new network segment and notice that LDP sessions are discovered but no sessions are established. Which issue is preventing the establishment of the LDP neighbors?

• A. The loopback addresses of the label switch routers are unavailable
• B. MPLS labels are not allocated for local routers
• C. IP Cisco Express Forwarding is disabled on the label switch routers
• D. An access link is blocking TCP port 711 on the MPLS routers

Answer: A

NEW QUESTION 7
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

Answer: C

NEW QUESTION 8
An engineer must configure a policy on a Cisco IOS XE router that achieves the following: Traffic 2 Mbps or less is transmitted
Traffic between 2 Mbps and 3 Mbps is marked with IP Precedence 4 Traffic that exceeds 3 Mbps is dropped
Which configuration achieves this policy?

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Answer: C

NEW QUESTION 9
Which option shows how a class map is implemented that matches only packets originating from the network 10.0.0.0/8, which are not marked as VoIP on Cisco IOS XE?
A)

B)

C)

D)

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Answer: B

NEW QUESTION 10
When implementing Cisco MPLS TE, the constrained-based path calculations will use which value as the TE cost of each link within the MPLS domain?

• A. By default, it will use the IGP metric, or each link can be assigned a specific value using the admin-weight command.
• B. It can only use the IGP metric as the TE cost.
• C. It will use the interface bandwidth as the TE cost.
• D. Each link must be assigned a TE cost using the metric command.

Answer: A

NEW QUESTION 11
DRAG DROP
You create an MPLS TE tunnel in IOS XR Software and want to configure forwarding on the tunnel. Drag the steps on the left to their correct order on the right.
Select and Place:

• A. Mastered
• B. Not Mastered

Answer: A

Explanation:

NEW QUESTION 12
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

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.

NEW QUESTION 13
Which statement defines how MPLS LDT Graceful Restart works after a service interruption?

• A. It works independent of neighboring routers to recover MPLS forwarding information
• B. It works by helping all neighboring MPLS LDP routers to recover MPLS forwarding information
• C. It works by helping neighboring routers with MPLS LDP SSO/NSF and Graceful Restart to recover MPLS forwarding information
• D. It works independent of neighboring non-LDP Graceful Restart routers to recover MPLS forwardinginformation

Answer: C

NEW QUESTION 14
Refer to the exhibit. Which configuration error prevents this traffic-shaping policy from working?

• 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.

Answer: B

NEW QUESTION 15
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

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) Â 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.

NEW QUESTION 16
An engineer is tasked to deploy Fast Reroute for Cisco MPLS TE. Which LSR is in charge to request the Fast Reroute capability along the LSP?

• A. point of local repair
• B. tail end router
• C. ingress and egress PE routers
• D. head-end router
• E. BGP routers acting as route reflectors

Answer: D

NEW QUESTION 17
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.

Answer: D

NEW QUESTION 18
Which configuration set enables outbound label filtering so that only peer 192.168.10.1 receives label
advertisements in an MPLS environment?
A)

B)

C)

D)

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Answer: C

NEW QUESTION 19
Which option is the appropriate way to configure a color-aware, dual-rate policer together with a color-blind, single-rate policer for the rest of the traffic?

• A. class-map match-all CLASS1 match dscp af31class-map match all CLASS2 match dscp af32class-map match-all CLASS3 match dscp efpolicy-map POLICY1 class CLASS1police rate 100000 peak-rate 200000conform-color CLASS2 exceed-color CLASS3conform-action set-dscp-transmit af11 exceed-action set-dscp-transmit af21 violate-action set-dscp-transmit af23
• B. class-map match-all CLASS 1 match dscp af31class-map match-all CLASS2 match dscp af32class-map match-all CLASS3 match dscp af33policy-map POLICY1 class CLASS1police rate 100000 burst 31250conform-color CLASS2 exceed-color CLASS3 conform-action set-dscp-transmit af11exceed-action set-dscp-transmit af21 violate-action set-dscp-transmit af23
• C. class-map match-all CLASS 1 match dscp af31 af32 af33class-map match-all CLASS2 match dscp af32class-map match-all CLASS3 match dscp af33policy-map POLICY1 class CLASS1police rate 100000 burst 31250conform-color CLASS2 exceed-color CLASS3 conform-action set-dscp-transmit af31exceed-action set-dscp-transmit af32 violate-action set-dscp-transmit af33 class class-defaultpolice rate percent 10 peak-rate percent 30
• D. class-map match-all CLASS 1 match dscp af31 af32 af33class-map match-all CLASS2 match dscp af32class-map match-all CLASS3 match dscp af33policy-map POLICY1 class CLASS1police rate 100000 peak-rate 200000conform-color CLASS2 exceed-color CLASS3 conform-action set-dscp-transmit af31exceed-action set-dscp-transmit af32 violate-action set-dscp-transmit af33 class class-defaultpolice rate percent 10 peak-rate percent 30
• E. class-map match-all CLASS 1 match dscp af31 af32 af33class-map match-all CLASS2 match dscp af32class-map match-all CLASS3 match dscp af33policy-map POLICY1 class CLASS1police rate 100000 peak-rate 200000conform-color CLASS2 exceed-color CLASS3 conform-action set-dscp-transmit af31exceed-action set-dscp-transmit af32 violate-action set-dscp-transmit af33 class class-defaultpolice rate 10000

Answer: E

NEW QUESTION 20
Refer to the exhibit. What happens to the traffic that exceeds the CIR?

• A. It is set an EXP value of 5 and transmitted
• B. It is set an EXP value of 5 and dropped
• C. It is set an EXP value of 0 and transmitted
• D. It is set an EXP value of 3 and dropped

Answer: C

NEW QUESTION 21
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