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Exam Code: JN0-664

Exam Name: Service Provider Routing and Switching, Professional (JNCIP-SP)

Certification Provider: Juniper

Corresponding Certification: JNCIP-SP

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Juniper JN0-664 Practice Test 44

Question 430

An operator changes the outer VLAN priority marking at a PE. Observed: The 802.1p priority observed downstream no longer matches the agreed enterprise service class. What evidence would validate recovery from this precise failure mode?

  1. Test packets on intended egress show correct markings and reverse traffic remains unchanged.
  2. Only the target guest class is capped while unrelated tenants keep their service rate.
  3. Matching application flows receive the same forwarding class regardless of incoming port.
  4. Downstream tag captures show the intended priority codepoint values.

Explanation

Correct Answer

D:

The intended result is Downstream tag captures show the intended priority codepoint values. It specifically verifies recovery from an egress ieee 802.1p rewrite map is absent or maps the wrong forwarding class, which produced the original symptom: The 802.1p priority observed downstream no longer matches the agreed enterprise service class. It is stronger evidence than a generic interface-up indicator.

Incorrect Answers

A:

This result is useful in another case with evidence Downstream peers see markings unchanged while reverse traffic is altered unexpectedly. It does not test recovery from the 802.1p priority observed downstream no longer matches the agreed enterprise service class. Check instead whether downstream tag captures show the intended priority codepoint values.

B:

It confirms an unrelated service correction: The policer was attached to a shared filter term rather than the customer's scoped traffic. The present case reports The 802.1p priority observed downstream no longer matches the agreed enterprise service class. Its completion test is Downstream tag captures show the intended priority codepoint values.

C:

That observation would verify a separate fault involving the firewall filter class action is attached on one ingress path but not the other. Its symptom is Traffic is classified correctly only on one interface even though both see identical flows. For this case the actual issue is an egress ieee 802.1p rewrite map is absent or maps the wrong forwarding class, and the relevant success signal is Downstream tag captures show the intended priority codepoint values.

Question 431

An operator changes the outer VLAN priority marking at a PE. Observed: The 802.1p priority observed downstream no longer matches the agreed enterprise service class. What underlying protocol or service configuration problem best explains the evidence?

  1. An egress IEEE 802.1p rewrite map is absent or maps the wrong forwarding class.
  2. The policer was attached to a shared filter term rather than the customer's scoped traffic.
  3. The firewall filter class action is attached on one ingress path but not the other.
  4. The rewrite rule was bound to an interface with the wrong outbound direction.

Explanation

Correct Answer

A:

Because the 802.1p priority observed downstream no longer matches the agreed enterprise service class, the likely cause is an egress ieee 802.1p rewrite map is absent or maps the wrong forwarding class. It is testable: Attach a coherent 802.1p rewrite policy for supported tagged egress frames. Expected follow-up: Downstream tag captures show the intended priority codepoint values.

Incorrect Answers

B:

The policer was attached to a shared filter term rather than the customer's scoped traffic. would normally be accompanied by a broad policer reduces throughput for other tenants on the same interface. The observed symptom is different: The 802.1p priority observed downstream no longer matches the agreed enterprise service class. The likely cause is An egress IEEE 802.1p rewrite map is absent or maps the wrong forwarding class.

C:

The stated cause is possible elsewhere but explains traffic is classified correctly only on one interface even though both see identical flows, not the 802.1p priority observed downstream no longer matches the agreed enterprise service class. This incident is better attributed to an egress ieee 802.1p rewrite map is absent or maps the wrong forwarding class.

D:

That explanation fits another condition: Downstream peers see markings unchanged while reverse traffic is altered unexpectedly. The evidence here is The 802.1p priority observed downstream no longer matches the agreed enterprise service class. Its closer root cause is An egress IEEE 802.1p rewrite map is absent or maps the wrong forwarding class.

Question 432

An operator changes the outer VLAN priority marking at a PE. Observed: The 802.1p priority observed downstream no longer matches the agreed enterprise service class. Which ongoing validation gate would best detect a recurrence of this problem?

  1. For each approved related change, verify that test packets on intended egress show correct markings and reverse traffic remains unchanged. Flag recurrence if downstream peers see markings unchanged while reverse traffic is altered unexpectedly.
  2. For each approved related change, verify that downstream tag captures show the intended priority codepoint values. Flag recurrence if the 802.1p priority observed downstream no longer matches the agreed enterprise service class.
  3. For each approved related change, verify that matching application flows receive the same forwarding class regardless of incoming port. Flag recurrence if traffic is classified correctly only on one interface even though both see identical flows.
  4. For each approved related change, verify that only the target guest class is capped while unrelated tenants keep their service rate. Flag recurrence if a broad policer reduces throughput for other tenants on the same interface.

Explanation

Correct Answer

B:

A useful regression gate tests whether downstream tag captures show the intended priority codepoint values and alerts when the 802.1p priority observed downstream no longer matches the agreed enterprise service class. This directly checks the technical weakness: An egress IEEE 802.1p rewrite map is absent or maps the wrong forwarding class. The gate is derived from the fictional incident and is not an independent Juniper engineer signoff.

Incorrect Answers

A:

It is valid for another service scenario but checks downstream peers see markings unchanged while reverse traffic is altered unexpectedly. This case instead needs a gate for the 802.1p priority observed downstream no longer matches the agreed enterprise service class and evidence that downstream tag captures show the intended priority codepoint values.

C:

The proposed control is tied to the firewall filter class action is attached on one ingress path but not the other, typically observed when traffic is classified correctly only on one interface even though both see identical flows. Here the target is an egress ieee 802.1p rewrite map is absent or maps the wrong forwarding class; monitor downstream tag captures show the intended priority codepoint values.

D:

This gate monitors a different failure, a broad policer reduces throughput for other tenants on the same interface. It would not detect the current problem: The 802.1p priority observed downstream no longer matches the agreed enterprise service class. The appropriate check requires downstream tag captures show the intended priority codepoint values.

Question 433

A provider uses multifield classification for an unmarked application. Observed: Traffic is classified correctly only on one interface even though both see identical flows. Which change most directly corrects the failure while respecting the existing service boundary?

  1. Map ingress forwarding class to the intended MPLS traffic-class marking consistently.
  2. Apply equivalent scoped classification filters to both intended ingress interfaces.
  3. Classify approved voice flows into a suitable forwarding class and assign a protected scheduler.
  4. Set the intended loss priority in the classifier or firewall filter actions.

Explanation

Correct Answer

B:

The observed condition is Traffic is classified correctly only on one interface even though both see identical flows. That indicates the firewall filter class action is attached on one ingress path but not the other. Applying the proposed remedy directly changes that condition. A concrete completion check is: Matching application flows receive the same forwarding class regardless of incoming port.

Incorrect Answers

A:

The option may be useful when the core no longer preserves premium treatment across label-switched paths, but that is not the current evidence. Here, traffic is classified correctly only on one interface even though both see identical flows, indicating the firewall filter class action is attached on one ingress path but not the other. The targeted action is Apply equivalent scoped classification filters to both intended ingress interfaces.

C:

This change belongs to a different Class of Service (CoS) issue: Voice jitter rises during backup bursts although interface errors are zero. That issue involves the default forwarding class treats latency-sensitive voice like best-effort traffic. The current symptom is Traffic is classified correctly only on one interface even though both see identical flows. It instead requires apply equivalent scoped classification filters to both intended ingress interfaces.

D:

This remediates the policy sets a forwarding class but omits the packet-loss priority action, normally indicated by Policer counters rise but the wrong loss-priority bit is set internally. It would leave the observed problem (Traffic is classified correctly only on one interface even though both see identical flows) unresolved. Address it with apply equivalent scoped classification filters to both intended ingress interfaces.

Question 434

A provider uses multifield classification for an unmarked application. Observed: Traffic is classified correctly only on one interface even though both see identical flows. After the correction, which result would most convincingly show that this fault is resolved?

  1. Matching application flows receive the same forwarding class regardless of incoming port.
  2. Voice delay and jitter stay within the service objective during measured backup load.
  3. Internal class and loss-priority counters match the policy for each sample flow.
  4. Core label captures and queue counters show the intended premium treatment.

Explanation

Correct Answer

A:

After apply equivalent scoped classification filters to both intended ingress interfaces, inspect whether matching application flows receive the same forwarding class regardless of incoming port. This closes the loop between the reported observation (Traffic is classified correctly only on one interface even though both see identical flows) and the underlying issue (The firewall filter class action is attached on one ingress path but not the other).

Incorrect Answers

B:

It confirms an unrelated service correction: The default forwarding class treats latency-sensitive voice like best-effort traffic. The present case reports Traffic is classified correctly only on one interface even though both see identical flows. Its completion test is Matching application flows receive the same forwarding class regardless of incoming port.

C:

This result is useful in another case with evidence Policer counters rise but the wrong loss-priority bit is set internally. It does not test recovery from traffic is classified correctly only on one interface even though both see identical flows. Check instead whether matching application flows receive the same forwarding class regardless of incoming port.

D:

That observation would verify a separate fault involving ip classification was configured but mpls exp or traffic-class encoding was omitted. Its symptom is The core no longer preserves premium treatment across label-switched paths. For this case the actual issue is the firewall filter class action is attached on one ingress path but not the other, and the relevant success signal is Matching application flows receive the same forwarding class regardless of incoming port.

Question 435

A provider uses multifield classification for an unmarked application. Observed: Traffic is classified correctly only on one interface even though both see identical flows. Which root cause is most consistent with this symptom?

  1. The policy sets a forwarding class but omits the packet-loss priority action.
  2. The firewall filter class action is attached on one ingress path but not the other.
  3. IP classification was configured but MPLS EXP or traffic-class encoding was omitted.
  4. The default forwarding class treats latency-sensitive voice like best-effort traffic.

Explanation

Correct Answer

B:

The reported evidence—Traffic is classified correctly only on one interface even though both see identical flows—supports the firewall filter class action is attached on one ingress path but not the other. The appropriate intervention is to apply equivalent scoped classification filters to both intended ingress interfaces, with confirmation from matching application flows receive the same forwarding class regardless of incoming port. Other causes require actual device-state verification.

Incorrect Answers

A:

That explanation fits another condition: Policer counters rise but the wrong loss-priority bit is set internally. The evidence here is Traffic is classified correctly only on one interface even though both see identical flows. Its closer root cause is The firewall filter class action is attached on one ingress path but not the other.

C:

The stated cause is possible elsewhere but explains the core no longer preserves premium treatment across label-switched paths, not traffic is classified correctly only on one interface even though both see identical flows. This incident is better attributed to the firewall filter class action is attached on one ingress path but not the other.

D:

The default forwarding class treats latency-sensitive voice like best-effort traffic. would normally be accompanied by voice jitter rises during backup bursts although interface errors are zero. The observed symptom is different: Traffic is classified correctly only on one interface even though both see identical flows. The likely cause is The firewall filter class action is attached on one ingress path but not the other.

Question 436

A provider uses multifield classification for an unmarked application. Observed: Traffic is classified correctly only on one interface even though both see identical flows. Which change-acceptance control is most relevant to preventing this exact failure?

  1. For each approved related change, verify that voice delay and jitter stay within the service objective during measured backup load. Flag recurrence if voice jitter rises during backup bursts although interface errors are zero.
  2. For each approved related change, verify that internal class and loss-priority counters match the policy for each sample flow. Flag recurrence if policer counters rise but the wrong loss-priority bit is set internally.
  3. For each approved related change, verify that matching application flows receive the same forwarding class regardless of incoming port. Flag recurrence if traffic is classified correctly only on one interface even though both see identical flows.
  4. For each approved related change, verify that core label captures and queue counters show the intended premium treatment. Flag recurrence if the core no longer preserves premium treatment across label-switched paths.

Explanation

Correct Answer

C:

The control is specific to the initial failure. It requires the result Matching application flows receive the same forwarding class regardless of incoming port. and treats Traffic is classified correctly only on one interface even though both see identical flows. as a failure signal. The causal concern is the firewall filter class action is attached on one ingress path but not the other.

Incorrect Answers

A:

This gate monitors a different failure, voice jitter rises during backup bursts although interface errors are zero. It would not detect the current problem: Traffic is classified correctly only on one interface even though both see identical flows. The appropriate check requires matching application flows receive the same forwarding class regardless of incoming port.

B:

It is valid for another service scenario but checks policer counters rise but the wrong loss-priority bit is set internally. This case instead needs a gate for traffic is classified correctly only on one interface even though both see identical flows and evidence that matching application flows receive the same forwarding class regardless of incoming port.

D:

The proposed control is tied to ip classification was configured but mpls exp or traffic-class encoding was omitted, typically observed when the core no longer preserves premium treatment across label-switched paths. Here the target is the firewall filter class action is attached on one ingress path but not the other; monitor matching application flows receive the same forwarding class regardless of incoming port.

Question 437

A WAN QoS filter counts packets by packet-loss priority. Observed: Policer counters rise but the wrong loss-priority bit is set internally. What should the routing engineer change first to address this particular symptom?

  1. Assign the correct per-customer scheduler profile and respect parent capacity.
  2. Set the intended loss priority in the classifier or firewall filter actions.
  3. Apply the correct DSCP classification mapping on the ingress logical interface.
  4. Define compatible ingress MPLS traffic-class classification for the peer contract.

Explanation

Correct Answer

B:

The decisive evidence is that Policer counters rise but the wrong loss-priority bit is set internally. This follows from the policy sets a forwarding class but omits the packet-loss priority action. The focused remedy is to set the intended loss priority in the classifier or firewall filter actions. Confirm improvement when internal class and loss-priority counters match the policy for each sample flow. Validate on an approved lab or change window before touching production.

Incorrect Answers

A:

This change belongs to a different Class of Service (CoS) issue: A new customer receives the same bandwidth guarantee as the largest existing customer. That issue involves tenant-facing scheduler profiles were copied without evaluating each contracted committed rate. The current symptom is Policer counters rise but the wrong loss-priority bit is set internally. It instead requires set the intended loss priority in the classifier or firewall filter actions.

C:

The option may be useful when traffic with a valid voice DSCP enters the default best-effort queue, but that is not the current evidence. Here, policer counters rise but the wrong loss-priority bit is set internally, indicating the policy sets a forwarding class but omits the packet-loss priority action. The targeted action is Set the intended loss priority in the classifier or firewall filter actions.

D:

This remediates the ingress exp classifier does not map provider labels to local forwarding classes, normally indicated by Premium traffic is delivered as best effort because the incoming label class is not decoded. It would leave the observed problem (Policer counters rise but the wrong loss-priority bit is set internally) unresolved. Address it with set the intended loss priority in the classifier or firewall filter actions.

Question 438

A WAN QoS filter counts packets by packet-loss priority. Observed: Policer counters rise but the wrong loss-priority bit is set internally. Which acceptance observation best confirms that the proposed change worked?

  1. Counters show voice packets in the intended forwarding class before egress scheduling.
  2. Measured per-customer service rates match the individual contracts under shared load.
  3. Premium label values map to the correct internal class and egress scheduler.
  4. Internal class and loss-priority counters match the policy for each sample flow.

Explanation

Correct Answer

D:

This acceptance criterion tests the actual fault. The source evidence was Policer counters rise but the wrong loss-priority bit is set internally. The correction addresses the policy sets a forwarding class but omits the packet-loss priority action; success requires internal class and loss-priority counters match the policy for each sample flow.

Incorrect Answers

A:

That observation would verify a separate fault involving a dscp classifier is not bound to the ingress traffic interface. Its symptom is Traffic with a valid voice DSCP enters the default best-effort queue. For this case the actual issue is the policy sets a forwarding class but omits the packet-loss priority action, and the relevant success signal is Internal class and loss-priority counters match the policy for each sample flow.

B:

It confirms an unrelated service correction: Tenant-facing scheduler profiles were copied without evaluating each contracted committed rate. The present case reports Policer counters rise but the wrong loss-priority bit is set internally. Its completion test is Internal class and loss-priority counters match the policy for each sample flow.

C:

This result is useful in another case with evidence Premium traffic is delivered as best effort because the incoming label class is not decoded. It does not test recovery from policer counters rise but the wrong loss-priority bit is set internally. Check instead whether internal class and loss-priority counters match the policy for each sample flow.

Question 439

A WAN QoS filter counts packets by packet-loss priority. Observed: Policer counters rise but the wrong loss-priority bit is set internally. What is the most likely source of the observed routing or service failure?

  1. A DSCP classifier is not bound to the ingress traffic interface.
  2. Tenant-facing scheduler profiles were copied without evaluating each contracted committed rate.
  3. The ingress EXP classifier does not map provider labels to local forwarding classes.
  4. The policy sets a forwarding class but omits the packet-loss priority action.

Explanation

Correct Answer

D:

This explanation is the closest match to the observed symptom: Policer counters rise but the wrong loss-priority bit is set internally. The specified root issue is The policy sets a forwarding class but omits the packet-loss priority action. Repair it through set the intended loss priority in the classifier or firewall filter actions, then check internal class and loss-priority counters match the policy for each sample flow.

Incorrect Answers

A:

The stated cause is possible elsewhere but explains traffic with a valid voice dscp enters the default best-effort queue, not policer counters rise but the wrong loss-priority bit is set internally. This incident is better attributed to the policy sets a forwarding class but omits the packet-loss priority action.

B:

Tenant-facing scheduler profiles were copied without evaluating each contracted committed rate. would normally be accompanied by a new customer receives the same bandwidth guarantee as the largest existing customer. The observed symptom is different: Policer counters rise but the wrong loss-priority bit is set internally. The likely cause is The policy sets a forwarding class but omits the packet-loss priority action.

C:

That explanation fits another condition: Premium traffic is delivered as best effort because the incoming label class is not decoded. The evidence here is Policer counters rise but the wrong loss-priority bit is set internally. Its closer root cause is The policy sets a forwarding class but omits the packet-loss priority action.

Question 440

A WAN QoS filter counts packets by packet-loss priority. Observed: Policer counters rise but the wrong loss-priority bit is set internally. What operational check best guards against this problem returning?

  1. For each approved related change, verify that measured per-customer service rates match the individual contracts under shared load. Flag recurrence if a new customer receives the same bandwidth guarantee as the largest existing customer.
  2. For each approved related change, verify that premium label values map to the correct internal class and egress scheduler. Flag recurrence if premium traffic is delivered as best effort because the incoming label class is not decoded.
  3. For each approved related change, verify that counters show voice packets in the intended forwarding class before egress scheduling. Flag recurrence if traffic with a valid voice DSCP enters the default best-effort queue.
  4. For each approved related change, verify that internal class and loss-priority counters match the policy for each sample flow. Flag recurrence if policer counters rise but the wrong loss-priority bit is set internally.

Explanation

Correct Answer

D:

This control asks for the same recovery evidence (Internal class and loss-priority counters match the policy for each sample flow) and flags recurrence of the same failure (Policer counters rise but the wrong loss-priority bit is set internally). It targets the underlying issue, the policy sets a forwarding class but omits the packet-loss priority action, rather than a different service problem. The exact cadence must be agreed with operations.

Incorrect Answers

A:

This gate monitors a different failure, a new customer receives the same bandwidth guarantee as the largest existing customer. It would not detect the current problem: Policer counters rise but the wrong loss-priority bit is set internally. The appropriate check requires internal class and loss-priority counters match the policy for each sample flow.

B:

It is valid for another service scenario but checks premium traffic is delivered as best effort because the incoming label class is not decoded. This case instead needs a gate for policer counters rise but the wrong loss-priority bit is set internally and evidence that internal class and loss-priority counters match the policy for each sample flow.

C:

The proposed control is tied to a dscp classifier is not bound to the ingress traffic interface, typically observed when traffic with a valid voice DSCP enters the default best-effort queue. Here the target is the policy sets a forwarding class but omits the packet-loss priority action; monitor internal class and loss-priority counters match the policy for each sample flow.

Service Provider Routing and Switching, Professional (JNCIP-SP) (JN0-664) Practice Tests