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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 25

Question 240

A customer AS wants to favor inbound traffic through one of two links. Observed: External peers continue choosing the wrong ingress despite local preference changes. Which ongoing validation gate would best detect a recurrence of this problem?

  1. For each approved related change, verify that inbound traffic converges to the agreed primary while the backup remains available. Flag recurrence if new prepended announcements do not influence the chosen inbound route.
  2. For each approved related change, verify that upstream route selection changes as validated by external path observations. Flag recurrence if external peers continue choosing the wrong ingress despite local preference changes.
  3. For each approved related change, verify that the recovered prefix becomes usable after permitted penalty decay without excessive flapping. Flag recurrence if a stable recovered prefix stays suppressed after several route updates.
  4. For each approved related change, verify that the permitted tagged route enters only the intended instance. Flag recurrence if a route arrives with the right community but enters the wrong routing instance.

Explanation

Correct Answer

B:

A useful regression gate tests whether upstream route selection changes as validated by external path observations and alerts when external peers continue choosing the wrong ingress despite local preference changes. This directly checks the technical weakness: Local preference is not exported to other autonomous systems. The gate is derived from the fictional incident and is not an independent Juniper engineer signoff.

Incorrect Answers

A:

The proposed control is tied to upstream local preference overrides the longer as-path signal, typically observed when new prepended announcements do not influence the chosen inbound route. Here the target is local preference is not exported to other autonomous systems; monitor upstream route selection changes as validated by external path observations.

C:

It is valid for another service scenario but checks a stable recovered prefix stays suppressed after several route updates. This case instead needs a gate for external peers continue choosing the wrong ingress despite local preference changes and evidence that upstream route selection changes as validated by external path observations.

D:

This gate monitors a different failure, a route arrives with the right community but enters the wrong routing instance. It would not detect the current problem: External peers continue choosing the wrong ingress despite local preference changes. The appropriate check requires upstream route selection changes as validated by external path observations.

Question 241

An enterprise using dual eBGP uplinks applies AS-path prepending. Observed: New prepended announcements do not influence the chosen inbound route. Which change most directly corrects the failure while respecting the existing service boundary?

  1. Confirm the applicable MED comparison rules and engineer a supported consistent policy.
  2. Establish permitted FlowSpec family and validation rules before accepting actions.
  3. Repair upstream next-hop resolution rather than forcing an arbitrary best path.
  4. Coordinate carrier-supported communities or accepted inbound steering methods.

Explanation

Correct Answer

D:

The observed condition is New prepended announcements do not influence the chosen inbound route. That indicates upstream local preference overrides the longer as-path signal. Applying the proposed remedy directly changes that condition. A concrete completion check is: Inbound traffic converges to the agreed primary while the backup remains available.

Incorrect Answers

A:

This remediates med comparison behavior depends on neighboring as and configured policies, normally indicated by The team expects a lower MED to win across different neighboring AS paths. It would leave the observed problem (New prepended announcements do not influence the chosen inbound route) unresolved. Address it with coordinate carrier-supported communities or accepted inbound steering methods.

B:

This change belongs to a different BGP issue: A FlowSpec announcement is present but the PE never applies the firewall action. That issue involves flowspec address-family negotiation or validation against unicast reachability fails. The current symptom is New prepended announcements do not influence the chosen inbound route. It instead requires coordinate carrier-supported communities or accepted inbound steering methods.

C:

The option may be useful when a route is not selected despite the upstream session remaining Established, but that is not the current evidence. Here, new prepended announcements do not influence the chosen inbound route, indicating upstream local preference overrides the longer as-path signal. The targeted action is Coordinate carrier-supported communities or accepted inbound steering methods.

Question 242

An enterprise using dual eBGP uplinks applies AS-path prepending. Observed: New prepended announcements do not influence the chosen inbound route. After the correction, which result would most convincingly show that this fault is resolved?

  1. Only authorized mitigation components are programmed in the forwarding plane.
  2. Route preference follows the documented comparison without unpredictable cross-AS assumptions.
  3. The preferred default has a valid resolved next hop and becomes active.
  4. Inbound traffic converges to the agreed primary while the backup remains available.

Explanation

Correct Answer

D:

After coordinate carrier-supported communities or accepted inbound steering methods, inspect whether inbound traffic converges to the agreed primary while the backup remains available. This closes the loop between the reported observation (New prepended announcements do not influence the chosen inbound route) and the underlying issue (Upstream local preference overrides the longer AS-path signal).

Incorrect Answers

A:

It confirms an unrelated service correction: FlowSpec address-family negotiation or validation against unicast reachability fails. The present case reports New prepended announcements do not influence the chosen inbound route. Its completion test is Inbound traffic converges to the agreed primary while the backup remains available.

B:

This result is useful in another case with evidence The team expects a lower MED to win across different neighboring AS paths. It does not test recovery from new prepended announcements do not influence the chosen inbound route. Check instead whether inbound traffic converges to the agreed primary while the backup remains available.

C:

That observation would verify a separate fault involving the competing next hop fails recursive reachability validation. Its symptom is A route is not selected despite the upstream session remaining Established. For this case the actual issue is upstream local preference overrides the longer as-path signal, and the relevant success signal is Inbound traffic converges to the agreed primary while the backup remains available.

Question 243

An enterprise using dual eBGP uplinks applies AS-path prepending. Observed: New prepended announcements do not influence the chosen inbound route. Which root cause is most consistent with this symptom?

  1. The competing next hop fails recursive reachability validation.
  2. MED comparison behavior depends on neighboring AS and configured policies.
  3. Upstream local preference overrides the longer AS-path signal.
  4. FlowSpec address-family negotiation or validation against unicast reachability fails.

Explanation

Correct Answer

C:

The reported evidence—New prepended announcements do not influence the chosen inbound route—supports upstream local preference overrides the longer as-path signal. The appropriate intervention is to coordinate carrier-supported communities or accepted inbound steering methods, with confirmation from inbound traffic converges to the agreed primary while the backup remains available. Other causes require actual device-state verification.

Incorrect Answers

A:

The stated cause is possible elsewhere but explains a route is not selected despite the upstream session remaining established, not new prepended announcements do not influence the chosen inbound route. This incident is better attributed to upstream local preference overrides the longer as-path signal.

B:

That explanation fits another condition: The team expects a lower MED to win across different neighboring AS paths. The evidence here is New prepended announcements do not influence the chosen inbound route. Its closer root cause is Upstream local preference overrides the longer AS-path signal.

D:

FlowSpec address-family negotiation or validation against unicast reachability fails. would normally be accompanied by a flowspec announcement is present but the pe never applies the firewall action. The observed symptom is different: New prepended announcements do not influence the chosen inbound route. The likely cause is Upstream local preference overrides the longer AS-path signal.

Question 244

An enterprise using dual eBGP uplinks applies AS-path prepending. Observed: New prepended announcements do not influence the chosen inbound route. Which change-acceptance control is most relevant to preventing this exact failure?

  1. For each approved related change, verify that the preferred default has a valid resolved next hop and becomes active. Flag recurrence if a route is not selected despite the upstream session remaining Established.
  2. For each approved related change, verify that only authorized mitigation components are programmed in the forwarding plane. Flag recurrence if a FlowSpec announcement is present but the PE never applies the firewall action.
  3. For each approved related change, verify that route preference follows the documented comparison without unpredictable cross-AS assumptions. Flag recurrence if the team expects a lower MED to win across different neighboring AS paths.
  4. For each approved related change, verify that inbound traffic converges to the agreed primary while the backup remains available. Flag recurrence if new prepended announcements do not influence the chosen inbound route.

Explanation

Correct Answer

D:

The control is specific to the initial failure. It requires the result Inbound traffic converges to the agreed primary while the backup remains available. and treats New prepended announcements do not influence the chosen inbound route. as a failure signal. The causal concern is upstream local preference overrides the longer as-path signal.

Incorrect Answers

A:

The proposed control is tied to the competing next hop fails recursive reachability validation, typically observed when a route is not selected despite the upstream session remaining Established. Here the target is upstream local preference overrides the longer as-path signal; monitor inbound traffic converges to the agreed primary while the backup remains available.

B:

This gate monitors a different failure, a flowspec announcement is present but the pe never applies the firewall action. It would not detect the current problem: New prepended announcements do not influence the chosen inbound route. The appropriate check requires inbound traffic converges to the agreed primary while the backup remains available.

C:

It is valid for another service scenario but checks the team expects a lower med to win across different neighboring as paths. This case instead needs a gate for new prepended announcements do not influence the chosen inbound route and evidence that inbound traffic converges to the agreed primary while the backup remains available.

Question 245

A BGP router compares two equally advertised destinations. Observed: The team expects a lower MED to win across different neighboring AS paths. What should the routing engineer change first to address this particular symptom?

  1. Use the contracted community value and enable the permitted community propagation.
  2. Apply a narrow import filter and prefix-limit according to the service agreement.
  3. Refine source/destination and protocol match components to the verified attack pattern.
  4. Confirm the applicable MED comparison rules and engineer a supported consistent policy.

Explanation

Correct Answer

D:

The decisive evidence is that The team expects a lower MED to win across different neighboring AS paths. This follows from med comparison behavior depends on neighboring as and configured policies. The focused remedy is to confirm the applicable MED comparison rules and engineer a supported consistent policy. Confirm improvement when route preference follows the documented comparison without unpredictable cross-AS assumptions. Validate on an approved lab or change window before touching production.

Incorrect Answers

A:

This change belongs to a different BGP issue: The upstream does not apply the agreed blackhole policy. That issue involves the carrier expects a different community value or route export suppresses communities. The current symptom is The team expects a lower MED to win across different neighboring AS paths. It instead requires confirm the applicable MED comparison rules and engineer a supported consistent policy.

B:

This remediates bgp inbound acceptance policy and max-prefix safety do not constrain the contracted feed, normally indicated by An unexpected memory spike occurs although only a few prefixes should be accepted. It would leave the observed problem (The team expects a lower MED to win across different neighboring AS paths) unresolved. Address it with confirm the applicable MED comparison rules and engineer a supported consistent policy.

C:

The option may be useful when normal customer traffic is dropped because the match covers the entire tenant aggregate, but that is not the current evidence. Here, the team expects a lower MED to win across different neighboring AS paths, indicating med comparison behavior depends on neighboring as and configured policies. The targeted action is Confirm the applicable MED comparison rules and engineer a supported consistent policy.

Question 246

A BGP router compares two equally advertised destinations. Observed: The team expects a lower MED to win across different neighboring AS paths. Which acceptance observation best confirms that the proposed change worked?

  1. The upstream confirms the intended tagged route receives the agreed action.
  2. RIB contains only contracted routes and resource usage returns to safe levels.
  3. Route preference follows the documented comparison without unpredictable cross-AS assumptions.
  4. The attack is filtered while unaffected flows remain reachable.

Explanation

Correct Answer

C:

This acceptance criterion tests the actual fault. The source evidence was The team expects a lower MED to win across different neighboring AS paths. The correction addresses med comparison behavior depends on neighboring as and configured policies; success requires route preference follows the documented comparison without unpredictable cross-AS assumptions.

Incorrect Answers

A:

It confirms an unrelated service correction: The carrier expects a different community value or route export suppresses communities. The present case reports The team expects a lower MED to win across different neighboring AS paths. Its completion test is Route preference follows the documented comparison without unpredictable cross-AS assumptions.

B:

This result is useful in another case with evidence An unexpected memory spike occurs although only a few prefixes should be accepted. It does not test recovery from the team expects a lower med to win across different neighboring as paths. Check instead whether route preference follows the documented comparison without unpredictable cross-AS assumptions.

D:

That observation would verify a separate fault involving flowspec match components are less specific than the approved attack signature. Its symptom is Normal customer traffic is dropped because the match covers the entire tenant aggregate. For this case the actual issue is med comparison behavior depends on neighboring as and configured policies, and the relevant success signal is Route preference follows the documented comparison without unpredictable cross-AS assumptions.

Question 247

A BGP router compares two equally advertised destinations. Observed: The team expects a lower MED to win across different neighboring AS paths. What is the most likely source of the observed routing or service failure?

  1. MED comparison behavior depends on neighboring AS and configured policies.
  2. The carrier expects a different community value or route export suppresses communities.
  3. FlowSpec match components are less specific than the approved attack signature.
  4. BGP inbound acceptance policy and max-prefix safety do not constrain the contracted feed.

Explanation

Correct Answer

A:

This explanation is the closest match to the observed symptom: The team expects a lower MED to win across different neighboring AS paths. The specified root issue is MED comparison behavior depends on neighboring AS and configured policies. Repair it through confirm the applicable MED comparison rules and engineer a supported consistent policy, then check route preference follows the documented comparison without unpredictable cross-AS assumptions.

Incorrect Answers

B:

The carrier expects a different community value or route export suppresses communities. would normally be accompanied by the upstream does not apply the agreed blackhole policy. The observed symptom is different: The team expects a lower MED to win across different neighboring AS paths. The likely cause is MED comparison behavior depends on neighboring AS and configured policies.

C:

The stated cause is possible elsewhere but explains normal customer traffic is dropped because the match covers the entire tenant aggregate, not the team expects a lower med to win across different neighboring as paths. This incident is better attributed to med comparison behavior depends on neighboring as and configured policies.

D:

That explanation fits another condition: An unexpected memory spike occurs although only a few prefixes should be accepted. The evidence here is The team expects a lower MED to win across different neighboring AS paths. Its closer root cause is MED comparison behavior depends on neighboring AS and configured policies.

Question 248

A BGP router compares two equally advertised destinations. Observed: The team expects a lower MED to win across different neighboring AS paths. What operational check best guards against this problem returning?

  1. For each approved related change, verify that the attack is filtered while unaffected flows remain reachable. Flag recurrence if normal customer traffic is dropped because the match covers the entire tenant aggregate.
  2. For each approved related change, verify that the upstream confirms the intended tagged route receives the agreed action. Flag recurrence if the upstream does not apply the agreed blackhole policy.
  3. For each approved related change, verify that route preference follows the documented comparison without unpredictable cross-AS assumptions. Flag recurrence if the team expects a lower MED to win across different neighboring AS paths.
  4. For each approved related change, verify that rIB contains only contracted routes and resource usage returns to safe levels. Flag recurrence if an unexpected memory spike occurs although only a few prefixes should be accepted.

Explanation

Correct Answer

C:

This control asks for the same recovery evidence (Route preference follows the documented comparison without unpredictable cross-AS assumptions) and flags recurrence of the same failure (The team expects a lower MED to win across different neighboring AS paths). It targets the underlying issue, med comparison behavior depends on neighboring as and configured policies, rather than a different service problem. The exact cadence must be agreed with operations.

Incorrect Answers

A:

The proposed control is tied to flowspec match components are less specific than the approved attack signature, typically observed when normal customer traffic is dropped because the match covers the entire tenant aggregate. Here the target is med comparison behavior depends on neighboring as and configured policies; monitor route preference follows the documented comparison without unpredictable cross-AS assumptions.

B:

This gate monitors a different failure, the upstream does not apply the agreed blackhole policy. It would not detect the current problem: The team expects a lower MED to win across different neighboring AS paths. The appropriate check requires route preference follows the documented comparison without unpredictable cross-AS assumptions.

D:

It is valid for another service scenario but checks an unexpected memory spike occurs although only a few prefixes should be accepted. This case instead needs a gate for the team expects a lower med to win across different neighboring as paths and evidence that route preference follows the documented comparison without unpredictable cross-AS assumptions.

Question 249

An operator attaches a standard BGP community to customer routes. Observed: The upstream does not apply the agreed blackhole policy. Which targeted remediation is most appropriate for the observed condition?

  1. Use the contracted community value and enable the permitted community propagation.
  2. Use supported large-community attributes and matching import/export policy.
  3. Review originator ID and cluster-list propagation and repair the client topology.
  4. Match local source address and remote neighbor definition with multihop permissions.

Explanation

Correct Answer

A:

This fix addresses the stated cause rather than an unrelated protocol. The reported symptom—The upstream does not apply the agreed blackhole policy—is consistent with the carrier expects a different community value or route export suppresses communities. Use the specified correction, then verify: The upstream confirms the intended tagged route receives the agreed action. Preserve existing policy and tenant isolation.

Incorrect Answers

B:

The option may be useful when a 32-bit community representation cannot encode the required triple of values, but that is not the current evidence. Here, the upstream does not apply the agreed blackhole policy, indicating the carrier expects a different community value or route export suppresses communities. The targeted action is Use the contracted community value and enable the permitted community propagation.

C:

This change belongs to a different BGP issue: Path oscillation appears between two route reflectors after clients are rearranged. That issue involves client and nonclient relationships were modified without controlling reflection loops. The current symptom is The upstream does not apply the agreed blackhole policy. It instead requires use the contracted community value and enable the permitted community propagation.

D:

This remediates update-source and reachability design disagree across the peers, normally indicated by One router silently sources TCP from a physical interface instead of its loopback. It would leave the observed problem (The upstream does not apply the agreed blackhole policy) unresolved. Address it with use the contracted community value and enable the permitted community propagation.

Question 250

An operator attaches a standard BGP community to customer routes. Observed: The upstream does not apply the agreed blackhole policy. What evidence would validate recovery from this precise failure mode?

  1. The session's TCP endpoint addresses match the planned loopback addresses.
  2. Reflected route attributes remain loop-free and no repeated re-advertisement occurs.
  3. The upstream confirms the intended tagged route receives the agreed action.
  4. The receiver sees the complete three-part community and classifies it correctly.

Explanation

Correct Answer

C:

The intended result is The upstream confirms the intended tagged route receives the agreed action. It specifically verifies recovery from the carrier expects a different community value or route export suppresses communities, which produced the original symptom: The upstream does not apply the agreed blackhole policy. It is stronger evidence than a generic interface-up indicator.

Incorrect Answers

A:

This result is useful in another case with evidence One router silently sources TCP from a physical interface instead of its loopback. It does not test recovery from the upstream does not apply the agreed blackhole policy. Check instead whether the upstream confirms the intended tagged route receives the agreed action.

B:

It confirms an unrelated service correction: Client and nonclient relationships were modified without controlling reflection loops. The present case reports The upstream does not apply the agreed blackhole policy. Its completion test is The upstream confirms the intended tagged route receives the agreed action.

D:

That observation would verify a separate fault involving standard communities do not provide the three-field large-community semantics. Its symptom is A 32-bit community representation cannot encode the required triple of values. For this case the actual issue is the carrier expects a different community value or route export suppresses communities, and the relevant success signal is The upstream confirms the intended tagged route receives the agreed action.

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