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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 8

Question 70

A provider injects a default route into a customer OSPF domain. Observed: Customer routing devices receive no default after the provider loses upstream connectivity. What evidence would validate recovery from this precise failure mode?

  1. All area neighbors form and the reduced external-LSA scope is as designed.
  2. Normal traffic favors the primary and failover selects backup only when intended.
  3. Customer default is present only under the permitted upstream condition.
  4. Remote best-path selection changes according to the documented E1 or E2 metric behavior.

Explanation

Correct Answer

C:

The intended result is Customer default is present only under the permitted upstream condition. It specifically verifies recovery from conditional default origination depends on a qualifying default route that is absent, which produced the original symptom: Customer routing devices receive no default after the provider loses upstream connectivity. It is stronger evidence than a generic interface-up indicator.

Incorrect Answers

A:

That observation would verify a separate fault involving area option bits in hellos do not agree with unchanged internal routers. Its symptom is A neighbor goes down directly after changing only the ABR area mode. For this case the actual issue is conditional default origination depends on a qualifying default route that is absent, and the relevant success signal is Customer default is present only under the permitted upstream condition.

B:

This result is useful in another case with evidence Backup traffic activates before the primary fiber has failed. It does not test recovery from customer routing devices receive no default after the provider loses upstream connectivity. Check instead whether customer default is present only under the permitted upstream condition.

D:

It confirms an unrelated service correction: Type-1 and type-2 external metric semantics were treated as interchangeable. The present case reports Customer routing devices receive no default after the provider loses upstream connectivity. Its completion test is Customer default is present only under the permitted upstream condition.

Question 71

A provider injects a default route into a customer OSPF domain. Observed: Customer routing devices receive no default after the provider loses upstream connectivity. What underlying protocol or service configuration problem best explains the evidence?

  1. The backup interface cost was inadvertently made lower during a maintenance template change.
  2. Area option bits in Hellos do not agree with unchanged internal routers.
  3. Conditional default origination depends on a qualifying default route that is absent.
  4. Type-1 and type-2 external metric semantics were treated as interchangeable.

Explanation

Correct Answer

C:

Because customer routing devices receive no default after the provider loses upstream connectivity, the likely cause is conditional default origination depends on a qualifying default route that is absent. It is testable: Restore valid upstream default reachability or explicitly define approved conditional origination. Expected follow-up: Customer default is present only under the permitted upstream condition.

Incorrect Answers

A:

That explanation fits another condition: Backup traffic activates before the primary fiber has failed. The evidence here is Customer routing devices receive no default after the provider loses upstream connectivity. Its closer root cause is Conditional default origination depends on a qualifying default route that is absent.

B:

The stated cause is possible elsewhere but explains a neighbor goes down directly after changing only the abr area mode, not customer routing devices receive no default after the provider loses upstream connectivity. This incident is better attributed to conditional default origination depends on a qualifying default route that is absent.

D:

Type-1 and type-2 external metric semantics were treated as interchangeable. would normally be accompanied by a remote router prefers an external route over the expected alternative only after a cost change. The observed symptom is different: Customer routing devices receive no default after the provider loses upstream connectivity. The likely cause is Conditional default origination depends on a qualifying default route that is absent.

Question 72

A provider injects a default route into a customer OSPF domain. Observed: Customer routing devices receive no default after the provider loses upstream connectivity. Which ongoing validation gate would best detect a recurrence of this problem?

  1. For each approved related change, verify that all area neighbors form and the reduced external-LSA scope is as designed. Flag recurrence if a neighbor goes down directly after changing only the ABR area mode.
  2. 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.
  3. For each approved related change, verify that customer default is present only under the permitted upstream condition. Flag recurrence if customer routing devices receive no default after the provider loses upstream connectivity.
  4. For each approved related change, verify that normal traffic favors the primary and failover selects backup only when intended. Flag recurrence if backup traffic activates before the primary fiber has failed.

Explanation

Correct Answer

C:

A useful regression gate tests whether customer default is present only under the permitted upstream condition and alerts when customer routing devices receive no default after the provider loses upstream connectivity. This directly checks the technical weakness: Conditional default origination depends on a qualifying default route that is absent. 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 area option bits in hellos do not agree with unchanged internal routers, typically observed when a neighbor goes down directly after changing only the ABR area mode. Here the target is conditional default origination depends on a qualifying default route that is absent; monitor customer default is present only under the permitted upstream condition.

B:

This gate monitors a different failure, a remote router prefers an external route over the expected alternative only after a cost change. It would not detect the current problem: Customer routing devices receive no default after the provider loses upstream connectivity. The appropriate check requires customer default is present only under the permitted upstream condition.

D:

It is valid for another service scenario but checks backup traffic activates before the primary fiber has failed. This case instead needs a gate for customer routing devices receive no default after the provider loses upstream connectivity and evidence that customer default is present only under the permitted upstream condition.

Question 73

An OSPF ABR is converting a standard area to a stub. Observed: A neighbor goes down directly after changing only the ABR area mode. Which change most directly corrects the failure while respecting the existing service boundary?

  1. Set a consistent higher reference bandwidth throughout the routing domain.
  2. Remove the unintended interarea leak and verify area summaries and route preferences.
  3. Establish OSPFv3 neighbor formation and advertise intended IPv6 prefixes on supported interfaces.
  4. Apply the consistent stub-area type to all routers in the area during the window.

Explanation

Correct Answer

D:

The observed condition is A neighbor goes down directly after changing only the ABR area mode. That indicates area option bits in hellos do not agree with unchanged internal routers. Applying the proposed remedy directly changes that condition. A concrete completion check is: All area neighbors form and the reduced external-LSA scope is as designed.

Incorrect Answers

A:

This remediates the common reference bandwidth is too small to distinguish modern line rates, normally indicated by Newly upgraded 100G and 10G links show identical calculated OSPF costs. It would leave the observed problem (A neighbor goes down directly after changing only the ABR area mode) unresolved. Address it with apply the consistent stub-area type to all routers in the area during the window.

B:

This change belongs to a different OSPF issue: Two ABRs forward the same prefix via different areas and traffic becomes asymmetrical. That issue involves an interarea route leaking policy introduced competing origin and preference paths. The current symptom is A neighbor goes down directly after changing only the ABR area mode. It instead requires apply the consistent stub-area type to all routers in the area during the window.

C:

The option may be useful when iPv6 prefixes never appear in the OSPF route table although IPv4 OSPF neighbors are healthy, but that is not the current evidence. Here, a neighbor goes down directly after changing only the ABR area mode, indicating area option bits in hellos do not agree with unchanged internal routers. The targeted action is Apply the consistent stub-area type to all routers in the area during the window.

Question 74

An OSPF ABR is converting a standard area to a stub. Observed: A neighbor goes down directly after changing only the ABR area mode. After the correction, which result would most convincingly show that this fault is resolved?

  1. Both directions use stable documented paths without unexpected duplicate interarea reachability.
  2. All area neighbors form and the reduced external-LSA scope is as designed.
  3. Derived costs differentiate the circuits and best-path selection follows expectations.
  4. IPv6 routes are installed with valid OSPFv3 next hops independent of OSPFv2.

Explanation

Correct Answer

B:

After apply the consistent stub-area type to all routers in the area during the window, inspect whether all area neighbors form and the reduced external-LSA scope is as designed. This closes the loop between the reported observation (A neighbor goes down directly after changing only the ABR area mode) and the underlying issue (Area option bits in Hellos do not agree with unchanged internal routers).

Incorrect Answers

A:

It confirms an unrelated service correction: An interarea route leaking policy introduced competing origin and preference paths. The present case reports A neighbor goes down directly after changing only the ABR area mode. Its completion test is All area neighbors form and the reduced external-LSA scope is as designed.

C:

This result is useful in another case with evidence Newly upgraded 100G and 10G links show identical calculated OSPF costs. It does not test recovery from a neighbor goes down directly after changing only the abr area mode. Check instead whether all area neighbors form and the reduced external-LSA scope is as designed.

D:

That observation would verify a separate fault involving ospfv3 protocol adjacency and ipv6 address-family enablement were not implemented. Its symptom is IPv6 prefixes never appear in the OSPF route table although IPv4 OSPF neighbors are healthy. For this case the actual issue is area option bits in hellos do not agree with unchanged internal routers, and the relevant success signal is All area neighbors form and the reduced external-LSA scope is as designed.

Question 75

An OSPF ABR is converting a standard area to a stub. Observed: A neighbor goes down directly after changing only the ABR area mode. Which root cause is most consistent with this symptom?

  1. The common reference bandwidth is too small to distinguish modern line rates.
  2. OSPFv3 protocol adjacency and IPv6 address-family enablement were not implemented.
  3. Area option bits in Hellos do not agree with unchanged internal routers.
  4. An interarea route leaking policy introduced competing origin and preference paths.

Explanation

Correct Answer

C:

The reported evidence—A neighbor goes down directly after changing only the ABR area mode—supports area option bits in hellos do not agree with unchanged internal routers. The appropriate intervention is to apply the consistent stub-area type to all routers in the area during the window, with confirmation from all area neighbors form and the reduced external-LSA scope is as designed. Other causes require actual device-state verification.

Incorrect Answers

A:

That explanation fits another condition: Newly upgraded 100G and 10G links show identical calculated OSPF costs. The evidence here is A neighbor goes down directly after changing only the ABR area mode. Its closer root cause is Area option bits in Hellos do not agree with unchanged internal routers.

B:

The stated cause is possible elsewhere but explains ipv6 prefixes never appear in the ospf route table although ipv4 ospf neighbors are healthy, not a neighbor goes down directly after changing only the abr area mode. This incident is better attributed to area option bits in hellos do not agree with unchanged internal routers.

D:

An interarea route leaking policy introduced competing origin and preference paths. would normally be accompanied by two abrs forward the same prefix via different areas and traffic becomes asymmetrical. The observed symptom is different: A neighbor goes down directly after changing only the ABR area mode. The likely cause is Area option bits in Hellos do not agree with unchanged internal routers.

Question 76

An OSPF ABR is converting a standard area to a stub. Observed: A neighbor goes down directly after changing only the ABR area mode. Which change-acceptance control is most relevant to preventing this exact failure?

  1. For each approved related change, verify that iPv6 routes are installed with valid OSPFv3 next hops independent of OSPFv2. Flag recurrence if iPv6 prefixes never appear in the OSPF route table although IPv4 OSPF neighbors are healthy.
  2. For each approved related change, verify that all area neighbors form and the reduced external-LSA scope is as designed. Flag recurrence if a neighbor goes down directly after changing only the ABR area mode.
  3. For each approved related change, verify that derived costs differentiate the circuits and best-path selection follows expectations. Flag recurrence if newly upgraded 100G and 10G links show identical calculated OSPF costs.
  4. For each approved related change, verify that both directions use stable documented paths without unexpected duplicate interarea reachability. Flag recurrence if two ABRs forward the same prefix via different areas and traffic becomes asymmetrical.

Explanation

Correct Answer

B:

The control is specific to the initial failure. It requires the result All area neighbors form and the reduced external-LSA scope is as designed. and treats A neighbor goes down directly after changing only the ABR area mode. as a failure signal. The causal concern is area option bits in hellos do not agree with unchanged internal routers.

Incorrect Answers

A:

The proposed control is tied to ospfv3 protocol adjacency and ipv6 address-family enablement were not implemented, typically observed when iPv6 prefixes never appear in the OSPF route table although IPv4 OSPF neighbors are healthy. Here the target is area option bits in hellos do not agree with unchanged internal routers; monitor all area neighbors form and the reduced external-LSA scope is as designed.

C:

It is valid for another service scenario but checks newly upgraded 100g and 10g links show identical calculated ospf costs. This case instead needs a gate for a neighbor goes down directly after changing only the abr area mode and evidence that all area neighbors form and the reduced external-LSA scope is as designed.

D:

This gate monitors a different failure, two abrs forward the same prefix via different areas and traffic becomes asymmetrical. It would not detect the current problem: A neighbor goes down directly after changing only the ABR area mode. The appropriate check requires all area neighbors form and the reduced external-LSA scope is as designed.

Question 77

An OSPF network uses reference bandwidth for link-cost derivation. Observed: Newly upgraded 100G and 10G links show identical calculated OSPF costs. What should the routing engineer change first to address this particular symptom?

  1. Choose a supported point-to-multipoint OSPF design and correct spoke next-hop assumptions.
  2. Set a consistent higher reference bandwidth throughout the routing domain.
  3. Correct the actual path MTU agreement rather than globally bypassing the MTU check.
  4. Verify matching OSPF interface network types and the proper neighbor-formation requirements.

Explanation

Correct Answer

B:

The decisive evidence is that Newly upgraded 100G and 10G links show identical calculated OSPF costs. This follows from the common reference bandwidth is too small to distinguish modern line rates. The focused remedy is to set a consistent higher reference bandwidth throughout the routing domain. Confirm improvement when derived costs differentiate the circuits and best-path selection follows expectations. Validate on an approved lab or change window before touching production.

Incorrect Answers

A:

This change belongs to a different OSPF issue: A spoke cannot reach another despite each hub-spoke neighbor being Full. That issue involves ospf network type or next-hop modeling does not reflect the hub-and-spoke topology. The current symptom is Newly upgraded 100G and 10G links show identical calculated OSPF costs. It instead requires set a consistent higher reference bandwidth throughout the routing domain.

C:

The option may be useful when the adjacency stays in ExStart after a router replacement with a different interface MTU, but that is not the current evidence. Here, newly upgraded 100G and 10G links show identical calculated OSPF costs, indicating the common reference bandwidth is too small to distinguish modern line rates. The targeted action is Set a consistent higher reference bandwidth throughout the routing domain.

D:

This remediates link network type and adjacency expectations do not match the actual segment design, normally indicated by The interface stays in 2-Way state although the operator expects a Full relationship. It would leave the observed problem (Newly upgraded 100G and 10G links show identical calculated OSPF costs) unresolved. Address it with set a consistent higher reference bandwidth throughout the routing domain.

Question 78

An OSPF network uses reference bandwidth for link-cost derivation. Observed: Newly upgraded 100G and 10G links show identical calculated OSPF costs. Which acceptance observation best confirms that the proposed change worked?

  1. Interspoke destinations resolve through expected paths and adjacencies remain healthy.
  2. Neighbors reach Full state and exchange the same database summaries.
  3. Adjacency reaches the state appropriate for the installed point-to-point design.
  4. Derived costs differentiate the circuits and best-path selection follows expectations.

Explanation

Correct Answer

D:

This acceptance criterion tests the actual fault. The source evidence was Newly upgraded 100G and 10G links show identical calculated OSPF costs. The correction addresses the common reference bandwidth is too small to distinguish modern line rates; success requires derived costs differentiate the circuits and best-path selection follows expectations.

Incorrect Answers

A:

It confirms an unrelated service correction: OSPF network type or next-hop modeling does not reflect the hub-and-spoke topology. The present case reports Newly upgraded 100G and 10G links show identical calculated OSPF costs. Its completion test is Derived costs differentiate the circuits and best-path selection follows expectations.

B:

That observation would verify a separate fault involving a database-description mtu mismatch prevents ospf database synchronization. Its symptom is The adjacency stays in ExStart after a router replacement with a different interface MTU. For this case the actual issue is the common reference bandwidth is too small to distinguish modern line rates, and the relevant success signal is Derived costs differentiate the circuits and best-path selection follows expectations.

C:

This result is useful in another case with evidence The interface stays in 2-Way state although the operator expects a Full relationship. It does not test recovery from newly upgraded 100g and 10g links show identical calculated ospf costs. Check instead whether derived costs differentiate the circuits and best-path selection follows expectations.

Question 79

An OSPF network uses reference bandwidth for link-cost derivation. Observed: Newly upgraded 100G and 10G links show identical calculated OSPF costs. What is the most likely source of the observed routing or service failure?

  1. The common reference bandwidth is too small to distinguish modern line rates.
  2. OSPF network type or next-hop modeling does not reflect the hub-and-spoke topology.
  3. A database-description MTU mismatch prevents OSPF database synchronization.
  4. Link network type and adjacency expectations do not match the actual segment design.

Explanation

Correct Answer

A:

This explanation is the closest match to the observed symptom: Newly upgraded 100G and 10G links show identical calculated OSPF costs. The specified root issue is The common reference bandwidth is too small to distinguish modern line rates. Repair it through set a consistent higher reference bandwidth throughout the routing domain, then check derived costs differentiate the circuits and best-path selection follows expectations.

Incorrect Answers

B:

OSPF network type or next-hop modeling does not reflect the hub-and-spoke topology. would normally be accompanied by a spoke cannot reach another despite each hub-spoke neighbor being full. The observed symptom is different: Newly upgraded 100G and 10G links show identical calculated OSPF costs. The likely cause is The common reference bandwidth is too small to distinguish modern line rates.

C:

The stated cause is possible elsewhere but explains the adjacency stays in exstart after a router replacement with a different interface mtu, not newly upgraded 100g and 10g links show identical calculated ospf costs. This incident is better attributed to the common reference bandwidth is too small to distinguish modern line rates.

D:

That explanation fits another condition: The interface stays in 2-Way state although the operator expects a Full relationship. The evidence here is Newly upgraded 100G and 10G links show identical calculated OSPF costs. Its closer root cause is The common reference bandwidth is too small to distinguish modern line rates.

Question 80

An OSPF network uses reference bandwidth for link-cost derivation. Observed: Newly upgraded 100G and 10G links show identical calculated OSPF costs. What operational check best guards against this problem returning?

  1. For each approved related change, verify that adjacency reaches the state appropriate for the installed point-to-point design. Flag recurrence if the interface stays in 2-Way state although the operator expects a Full relationship.
  2. For each approved related change, verify that derived costs differentiate the circuits and best-path selection follows expectations. Flag recurrence if newly upgraded 100G and 10G links show identical calculated OSPF costs.
  3. For each approved related change, verify that interspoke destinations resolve through expected paths and adjacencies remain healthy. Flag recurrence if a spoke cannot reach another despite each hub-spoke neighbor being Full.
  4. For each approved related change, verify that neighbors reach Full state and exchange the same database summaries. Flag recurrence if the adjacency stays in ExStart after a router replacement with a different interface MTU.

Explanation

Correct Answer

B:

This control asks for the same recovery evidence (Derived costs differentiate the circuits and best-path selection follows expectations) and flags recurrence of the same failure (Newly upgraded 100G and 10G links show identical calculated OSPF costs). It targets the underlying issue, the common reference bandwidth is too small to distinguish modern line rates, 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 the interface stays in 2-way state although the operator expects a full relationship. This case instead needs a gate for newly upgraded 100g and 10g links show identical calculated ospf costs and evidence that derived costs differentiate the circuits and best-path selection follows expectations.

C:

This gate monitors a different failure, a spoke cannot reach another despite each hub-spoke neighbor being full. It would not detect the current problem: Newly upgraded 100G and 10G links show identical calculated OSPF costs. The appropriate check requires derived costs differentiate the circuits and best-path selection follows expectations.

D:

The proposed control is tied to a database-description mtu mismatch prevents ospf database synchronization, typically observed when the adjacency stays in ExStart after a router replacement with a different interface MTU. Here the target is the common reference bandwidth is too small to distinguish modern line rates; monitor derived costs differentiate the circuits and best-path selection follows expectations.

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