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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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"Service Provider Routing and Switching, Professional (JNCIP-SP) Exam", also known as JN0-664 exam, is a Juniper certification exam.

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Juniper JN0-664 Practice Test 3

Question 20

A core changes its OSPF backbone topology during ring restoration. Observed: One nonbackbone area becomes unreachable although all its local neighbors remain Full. What operational check best guards against this problem returning?

  1. For each approved related change, verify that the exception installs independently while the intended aggregate is retained. Flag recurrence if one exception prefix within a summarized block disappears after consolidation.
  2. For each approved related change, verify that the chosen route and forwarding next hop match the documented cost comparison. Flag recurrence if traffic keeps using a longer-delay path after a higher-speed circuit is installed.
  3. For each approved related change, verify that lSDB router LSA identities are unique and all intended neighbors become Full. Flag recurrence if two nodes advertise the same router ID and neighbor behavior becomes unstable.
  4. For each approved related change, verify that interarea destinations return without introducing disconnected backbone islands. Flag recurrence if one nonbackbone area becomes unreachable although all its local neighbors remain Full.

Explanation

Correct Answer

D:

This control asks for the same recovery evidence (Interarea destinations return without introducing disconnected backbone islands) and flags recurrence of the same failure (One nonbackbone area becomes unreachable although all its local neighbors remain Full). It targets the underlying issue, the area no longer has a continuous logical attachment to area 0, rather than a different service problem. The exact cadence must be agreed with operations.

Incorrect Answers

A:

It is valid for another service scenario but checks one exception prefix within a summarized block disappears after consolidation. This case instead needs a gate for one nonbackbone area becomes unreachable although all its local neighbors remain full and evidence that interarea destinations return without introducing disconnected backbone islands.

B:

This gate monitors a different failure, traffic keeps using a longer-delay path after a higher-speed circuit is installed. It would not detect the current problem: One nonbackbone area becomes unreachable although all its local neighbors remain Full. The appropriate check requires interarea destinations return without introducing disconnected backbone islands.

C:

The proposed control is tied to duplicate ospf router ids prevent unambiguous lsa ownership, typically observed when two nodes advertise the same router ID and neighbor behavior becomes unstable. Here the target is the area no longer has a continuous logical attachment to area 0; monitor interarea destinations return without introducing disconnected backbone islands.

Question 21

Two backbone OSPF paths reach an upstream server prefix. Observed: Traffic keeps using a longer-delay path after a higher-speed circuit is installed. Which targeted remediation is most appropriate for the observed condition?

  1. Inspect ABR area range aggregation and withdraw or adjust the summary to match actual components.
  2. Align the actual hello/dead intervals and inspect received Hello parameter fields.
  3. Adjust interface OSPF costs consistently on both transit paths and review resulting shortest paths.
  4. Compare RIB, FIB and adjacency state and clear the identified stale forwarding entry safely.

Explanation

Correct Answer

C:

This fix addresses the stated cause rather than an unrelated protocol. The reported symptom—Traffic keeps using a longer-delay path after a higher-speed circuit is installed—is consistent with interface costs still reflect old capacity assumptions instead of the operator's intended metric model. Use the specified correction, then verify: The chosen route and forwarding next hop match the documented cost comparison. Preserve existing policy and tenant isolation.

Incorrect Answers

A:

The option may be useful when a withdrawn subnet is still reachable through a discard next hop on the summarizing router, but that is not the current evidence. Here, traffic keeps using a longer-delay path after a higher-speed circuit is installed, indicating interface costs still reflect old capacity assumptions instead of the operator's intended metric model. The targeted action is Adjust interface OSPF costs consistently on both transit paths and review resulting shortest paths.

B:

This remediates hello and dead timer settings differ across the candidate neighbors, normally indicated by One neighbor never forms adjacency although ping and VLAN connectivity work. It would leave the observed problem (Traffic keeps using a longer-delay path after a higher-speed circuit is installed) unresolved. Address it with adjust interface OSPF costs consistently on both transit paths and review resulting shortest paths.

D:

This change belongs to a different OSPF issue: The RIB points at a reachable next hop but the FIB sends traffic into a loop. That issue involves a forwarding inconsistency persists after the ospf topology converged. The current symptom is Traffic keeps using a longer-delay path after a higher-speed circuit is installed. It instead requires adjust interface OSPF costs consistently on both transit paths and review resulting shortest paths.

Question 22

Two backbone OSPF paths reach an upstream server prefix. Observed: Traffic keeps using a longer-delay path after a higher-speed circuit is installed. What evidence would validate recovery from this precise failure mode?

  1. Withdrawn component routes do not remain falsely reachable through the advertised aggregate.
  2. Forwarding follows the installed shortest path without repeated loops.
  3. The chosen route and forwarding next hop match the documented cost comparison.
  4. Adjacencies form normally without relying on reduced safety checks.

Explanation

Correct Answer

C:

The intended result is The chosen route and forwarding next hop match the documented cost comparison. It specifically verifies recovery from interface costs still reflect old capacity assumptions instead of the operator's intended metric model, which produced the original symptom: Traffic keeps using a longer-delay path after a higher-speed circuit is installed. It is stronger evidence than a generic interface-up indicator.

Incorrect Answers

A:

That observation would verify a separate fault involving the summary remains advertised while the more-specific reachability condition is inconsistent. Its symptom is A withdrawn subnet is still reachable through a discard next hop on the summarizing router. For this case the actual issue is interface costs still reflect old capacity assumptions instead of the operator's intended metric model, and the relevant success signal is The chosen route and forwarding next hop match the documented cost comparison.

B:

It confirms an unrelated service correction: A forwarding inconsistency persists after the OSPF topology converged. The present case reports Traffic keeps using a longer-delay path after a higher-speed circuit is installed. Its completion test is The chosen route and forwarding next hop match the documented cost comparison.

D:

This result is useful in another case with evidence One neighbor never forms adjacency although ping and VLAN connectivity work. It does not test recovery from traffic keeps using a longer-delay path after a higher-speed circuit is installed. Check instead whether the chosen route and forwarding next hop match the documented cost comparison.

Question 23

Two backbone OSPF paths reach an upstream server prefix. Observed: Traffic keeps using a longer-delay path after a higher-speed circuit is installed. What underlying protocol or service configuration problem best explains the evidence?

  1. A forwarding inconsistency persists after the OSPF topology converged.
  2. Hello and dead timer settings differ across the candidate neighbors.
  3. The summary remains advertised while the more-specific reachability condition is inconsistent.
  4. Interface costs still reflect old capacity assumptions instead of the operator's intended metric model.

Explanation

Correct Answer

D:

Because traffic keeps using a longer-delay path after a higher-speed circuit is installed, the likely cause is interface costs still reflect old capacity assumptions instead of the operator's intended metric model. It is testable: Adjust interface OSPF costs consistently on both transit paths and review resulting shortest paths. Expected follow-up: The chosen route and forwarding next hop match the documented cost comparison.

Incorrect Answers

A:

A forwarding inconsistency persists after the OSPF topology converged. would normally be accompanied by the rib points at a reachable next hop but the fib sends traffic into a loop. The observed symptom is different: Traffic keeps using a longer-delay path after a higher-speed circuit is installed. The likely cause is Interface costs still reflect old capacity assumptions instead of the operator's intended metric model.

B:

That explanation fits another condition: One neighbor never forms adjacency although ping and VLAN connectivity work. The evidence here is Traffic keeps using a longer-delay path after a higher-speed circuit is installed. Its closer root cause is Interface costs still reflect old capacity assumptions instead of the operator's intended metric model.

C:

The stated cause is possible elsewhere but explains a withdrawn subnet is still reachable through a discard next hop on the summarizing router, not traffic keeps using a longer-delay path after a higher-speed circuit is installed. This incident is better attributed to interface costs still reflect old capacity assumptions instead of the operator's intended metric model.

Question 24

Two backbone OSPF paths reach an upstream server prefix. Observed: Traffic keeps using a longer-delay path after a higher-speed circuit is installed. Which ongoing validation gate would best detect a recurrence of this problem?

  1. For each approved related change, verify that withdrawn component routes do not remain falsely reachable through the advertised aggregate. Flag recurrence if a withdrawn subnet is still reachable through a discard next hop on the summarizing router.
  2. For each approved related change, verify that adjacencies form normally without relying on reduced safety checks. Flag recurrence if one neighbor never forms adjacency although ping and VLAN connectivity work.
  3. For each approved related change, verify that forwarding follows the installed shortest path without repeated loops. Flag recurrence if the RIB points at a reachable next hop but the FIB sends traffic into a loop.
  4. For each approved related change, verify that the chosen route and forwarding next hop match the documented cost comparison. Flag recurrence if traffic keeps using a longer-delay path after a higher-speed circuit is installed.

Explanation

Correct Answer

D:

A useful regression gate tests whether the chosen route and forwarding next hop match the documented cost comparison and alerts when traffic keeps using a longer-delay path after a higher-speed circuit is installed. This directly checks the technical weakness: Interface costs still reflect old capacity assumptions instead of the operator's intended metric model. 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 the summary remains advertised while the more-specific reachability condition is inconsistent, typically observed when a withdrawn subnet is still reachable through a discard next hop on the summarizing router. Here the target is interface costs still reflect old capacity assumptions instead of the operator's intended metric model; monitor the chosen route and forwarding next hop match the documented cost comparison.

B:

It is valid for another service scenario but checks one neighbor never forms adjacency although ping and vlan connectivity work. This case instead needs a gate for traffic keeps using a longer-delay path after a higher-speed circuit is installed and evidence that the chosen route and forwarding next hop match the documented cost comparison.

C:

This gate monitors a different failure, the rib points at a reachable next hop but the fib sends traffic into a loop. It would not detect the current problem: Traffic keeps using a longer-delay path after a higher-speed circuit is installed. The appropriate check requires the chosen route and forwarding next hop match the documented cost comparison.

Question 25

A provider ABR summarizes a customer aggregate into area 0. Observed: A withdrawn subnet is still reachable through a discard next hop on the summarizing router. Which change most directly corrects the failure while respecting the existing service boundary?

  1. Configure the customer-facing interface as passive while retaining its connected-prefix advertisement.
  2. Check actual OSPF path cost and supported ECMP configuration before enabling both.
  3. Use the intended external metric type and verify the internal cost contribution to selection.
  4. Inspect ABR area range aggregation and withdraw or adjust the summary to match actual components.

Explanation

Correct Answer

D:

The observed condition is A withdrawn subnet is still reachable through a discard next hop on the summarizing router. That indicates the summary remains advertised while the more-specific reachability condition is inconsistent. Applying the proposed remedy directly changes that condition. A concrete completion check is: Withdrawn component routes do not remain falsely reachable through the advertised aggregate.

Incorrect Answers

A:

This change belongs to a different OSPF issue: A multicast Hello is sent into the customer VLAN during onboarding. That issue involves ospf was enabled for route advertisement but the interface was not made passive. The current symptom is A withdrawn subnet is still reachable through a discard next hop on the summarizing router. It instead requires inspect ABR area range aggregation and withdraw or adjust the summary to match actual components.

B:

The option may be useful when only one of two intended equal-cost paths is used after topology changes, but that is not the current evidence. Here, a withdrawn subnet is still reachable through a discard next hop on the summarizing router, indicating the summary remains advertised while the more-specific reachability condition is inconsistent. The targeted action is Inspect ABR area range aggregation and withdraw or adjust the summary to match actual components.

C:

This remediates type-1 and type-2 external metric semantics were treated as interchangeable, normally indicated by A remote router prefers an external route over the expected alternative only after a cost change. It would leave the observed problem (A withdrawn subnet is still reachable through a discard next hop on the summarizing router) unresolved. Address it with inspect ABR area range aggregation and withdraw or adjust the summary to match actual components.

Question 26

A provider ABR summarizes a customer aggregate into area 0. Observed: A withdrawn subnet is still reachable through a discard next hop on the summarizing router. After the correction, which result would most convincingly show that this fault is resolved?

  1. Remote best-path selection changes according to the documented E1 or E2 metric behavior.
  2. Withdrawn component routes do not remain falsely reachable through the advertised aggregate.
  3. The route table lists both intended equal-cost next hops and traffic distribution behaves as designed.
  4. No OSPF Hellos leave the interface and permitted internal routes remain advertised.

Explanation

Correct Answer

B:

After inspect ABR area range aggregation and withdraw or adjust the summary to match actual components, inspect whether withdrawn component routes do not remain falsely reachable through the advertised aggregate. This closes the loop between the reported observation (A withdrawn subnet is still reachable through a discard next hop on the summarizing router) and the underlying issue (The summary remains advertised while the more-specific reachability condition is inconsistent).

Incorrect Answers

A:

This result is useful in another case with evidence A remote router prefers an external route over the expected alternative only after a cost change. It does not test recovery from a withdrawn subnet is still reachable through a discard next hop on the summarizing router. Check instead whether withdrawn component routes do not remain falsely reachable through the advertised aggregate.

C:

That observation would verify a separate fault involving the route metrics are unequal or forwarding ecmp limits do not allow the second path. Its symptom is Only one of two intended equal-cost paths is used after topology changes. For this case the actual issue is the summary remains advertised while the more-specific reachability condition is inconsistent, and the relevant success signal is Withdrawn component routes do not remain falsely reachable through the advertised aggregate.

D:

It confirms an unrelated service correction: OSPF was enabled for route advertisement but the interface was not made passive. The present case reports A withdrawn subnet is still reachable through a discard next hop on the summarizing router. Its completion test is Withdrawn component routes do not remain falsely reachable through the advertised aggregate.

Question 27

A provider ABR summarizes a customer aggregate into area 0. Observed: A withdrawn subnet is still reachable through a discard next hop on the summarizing router. Which root cause is most consistent with this symptom?

  1. The summary remains advertised while the more-specific reachability condition is inconsistent.
  2. Type-1 and type-2 external metric semantics were treated as interchangeable.
  3. The route metrics are unequal or forwarding ECMP limits do not allow the second path.
  4. OSPF was enabled for route advertisement but the interface was not made passive.

Explanation

Correct Answer

A:

The reported evidence—A withdrawn subnet is still reachable through a discard next hop on the summarizing router—supports the summary remains advertised while the more-specific reachability condition is inconsistent. The appropriate intervention is to inspect ABR area range aggregation and withdraw or adjust the summary to match actual components, with confirmation from withdrawn component routes do not remain falsely reachable through the advertised aggregate. Other causes require actual device-state verification.

Incorrect Answers

B:

That explanation fits another condition: A remote router prefers an external route over the expected alternative only after a cost change. The evidence here is A withdrawn subnet is still reachable through a discard next hop on the summarizing router. Its closer root cause is The summary remains advertised while the more-specific reachability condition is inconsistent.

C:

The stated cause is possible elsewhere but explains only one of two intended equal-cost paths is used after topology changes, not a withdrawn subnet is still reachable through a discard next hop on the summarizing router. This incident is better attributed to the summary remains advertised while the more-specific reachability condition is inconsistent.

D:

OSPF was enabled for route advertisement but the interface was not made passive. would normally be accompanied by a multicast hello is sent into the customer vlan during onboarding. The observed symptom is different: A withdrawn subnet is still reachable through a discard next hop on the summarizing router. The likely cause is The summary remains advertised while the more-specific reachability condition is inconsistent.

Question 28

A provider ABR summarizes a customer aggregate into area 0. Observed: A withdrawn subnet is still reachable through a discard next hop on the summarizing router. Which change-acceptance control is most relevant to preventing this exact failure?

  1. For each approved related change, verify that the route table lists both intended equal-cost next hops and traffic distribution behaves as designed. Flag recurrence if only one of two intended equal-cost paths is used after topology changes.
  2. For each approved related change, verify that withdrawn component routes do not remain falsely reachable through the advertised aggregate. Flag recurrence if a withdrawn subnet is still reachable through a discard next hop on the summarizing router.
  3. For each approved related change, verify that no OSPF Hellos leave the interface and permitted internal routes remain advertised. Flag recurrence if a multicast Hello is sent into the customer VLAN during onboarding.
  4. For each approved related change, verify that remote best-path selection changes according to the documented E1 or E2 metric behavior. Flag recurrence if a remote router prefers an external route over the expected alternative only after a cost change.

Explanation

Correct Answer

B:

The control is specific to the initial failure. It requires the result Withdrawn component routes do not remain falsely reachable through the advertised aggregate. and treats A withdrawn subnet is still reachable through a discard next hop on the summarizing router. as a failure signal. The causal concern is the summary remains advertised while the more-specific reachability condition is inconsistent.

Incorrect Answers

A:

The proposed control is tied to the route metrics are unequal or forwarding ecmp limits do not allow the second path, typically observed when only one of two intended equal-cost paths is used after topology changes. Here the target is the summary remains advertised while the more-specific reachability condition is inconsistent; monitor withdrawn component routes do not remain falsely reachable through the advertised aggregate.

C:

This gate monitors a different failure, a multicast hello is sent into the customer vlan during onboarding. It would not detect the current problem: A withdrawn subnet is still reachable through a discard next hop on the summarizing router. The appropriate check requires withdrawn component routes do not remain falsely reachable through the advertised aggregate.

D:

It is valid for another service scenario but checks a remote router prefers an external route over the expected alternative only after a cost change. This case instead needs a gate for a withdrawn subnet is still reachable through a discard next hop on the summarizing router and evidence that withdrawn component routes do not remain falsely reachable through the advertised aggregate.

Question 29

An ASBR redistributes static test networks into OSPF. Observed: A remote router prefers an external route over the expected alternative only after a cost change. What should the routing engineer change first to address this particular symptom?

  1. Rebuild valid area membership and confirm the ABR's backbone reachability.
  2. Establish OSPFv3 neighbor formation and advertise intended IPv6 prefixes on supported interfaces.
  3. Reconcile link-state database state using supported neighbor reset and source-of-LSA checks.
  4. Use the intended external metric type and verify the internal cost contribution to selection.

Explanation

Correct Answer

D:

The decisive evidence is that A remote router prefers an external route over the expected alternative only after a cost change. This follows from type-1 and type-2 external metric semantics were treated as interchangeable. The focused remedy is to use the intended external metric type and verify the internal cost contribution to selection. Confirm improvement when remote best-path selection changes according to the documented E1 or E2 metric behavior. Validate on an approved lab or change window before touching production.

Incorrect Answers

A:

The option may be useful when summaries from area 2 fail to propagate even though the transit neighbor is operational, but that is not the current evidence. Here, a remote router prefers an external route over the expected alternative only after a cost change, indicating type-1 and type-2 external metric semantics were treated as interchangeable. The targeted action is Use the intended external metric type and verify the internal cost contribution to selection.

B:

This change belongs to a different OSPF issue: IPv6 prefixes never appear in the OSPF route table although IPv4 OSPF neighbors are healthy. That issue involves ospfv3 protocol adjacency and ipv6 address-family enablement were not implemented. The current symptom is A remote router prefers an external route over the expected alternative only after a cost change. It instead requires use the intended external metric type and verify the internal cost contribution to selection.

C:

This remediates a stale lsdb instance and lsa sequence interaction are preventing clean convergence, normally indicated by Several neighbors repeatedly exchange database descriptions without completing synchronization. It would leave the observed problem (A remote router prefers an external route over the expected alternative only after a cost change) unresolved. Address it with use the intended external metric type and verify the internal cost contribution to selection.

Question 30

An ASBR redistributes static test networks into OSPF. Observed: A remote router prefers an external route over the expected alternative only after a cost change. Which acceptance observation best confirms that the proposed change worked?

  1. The LSDB converges to matching current LSA instances and neighbors remain Full.
  2. IPv6 routes are installed with valid OSPFv3 next hops independent of OSPFv2.
  3. Summaries appear with consistent area origin and the transit maintains Full neighbor state.
  4. Remote best-path selection changes according to the documented E1 or E2 metric behavior.

Explanation

Correct Answer

D:

This acceptance criterion tests the actual fault. The source evidence was A remote router prefers an external route over the expected alternative only after a cost change. The correction addresses type-1 and type-2 external metric semantics were treated as interchangeable; success requires remote best-path selection changes according to the documented E1 or E2 metric behavior.

Incorrect Answers

A:

This result is useful in another case with evidence Several neighbors repeatedly exchange database descriptions without completing synchronization. It does not test recovery from a remote router prefers an external route over the expected alternative only after a cost change. Check instead whether remote best-path selection changes according to the documented E1 or E2 metric behavior.

B:

It confirms an unrelated service correction: OSPFv3 protocol adjacency and IPv6 address-family enablement were not implemented. The present case reports A remote router prefers an external route over the expected alternative only after a cost change. Its completion test is Remote best-path selection changes according to the documented E1 or E2 metric behavior.

C:

That observation would verify a separate fault involving the device is not a valid abr with an area 0 logical path. Its symptom is Summaries from area 2 fail to propagate even though the transit neighbor is operational. For this case the actual issue is type-1 and type-2 external metric semantics were treated as interchangeable, and the relevant success signal is Remote best-path selection changes according to the documented E1 or E2 metric behavior.

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