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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 13

Question 120

A new IS-IS site is added to an existing common core. Observed: Neighbors remain Down even though interface transport and timers match. Which ongoing validation gate would best detect a recurrence of this problem?

  1. For each approved related change, verify that neighbor adjacency forms at the intended level and LSDB distribution is correct. Flag recurrence if neighbors remain Down even though interface transport and timers match.
  2. For each approved related change, verify that the configured level adjacencies become operational and level-specific databases are populated. Flag recurrence if one neighbor reports only a Level 2 adjacency despite the access level being required.
  3. For each approved related change, verify that route origin stays stable across peers and protocol feedback ceases. Flag recurrence if the route repeatedly returns to the protocol it came from.
  4. For each approved related change, verify that pseudonode LSP ownership stabilizes on the approved designated router. Flag recurrence if a maintenance router unexpectedly controls pseudonode LSP generation.

Explanation

Correct Answer

A:

A useful regression gate tests whether neighbor adjacency forms at the intended level and LSDB distribution is correct and alerts when neighbors remain Down even though interface transport and timers match. This directly checks the technical weakness: NET area identifiers disagree for intended Level 1 adjacency. The gate is derived from the fictional incident and is not an independent Juniper engineer signoff.

Incorrect Answers

B:

It is valid for another service scenario but checks one neighbor reports only a level 2 adjacency despite the access level being required. This case instead needs a gate for neighbors remain down even though interface transport and timers match and evidence that neighbor adjacency forms at the intended level and LSDB distribution is correct.

C:

This gate monitors a different failure, the route repeatedly returns to the protocol it came from. It would not detect the current problem: Neighbors remain Down even though interface transport and timers match. The appropriate check requires neighbor adjacency forms at the intended level and LSDB distribution is correct.

D:

The proposed control is tied to dis priority and tie-break criteria were not considered in interface design, typically observed when a maintenance router unexpectedly controls pseudonode LSP generation. Here the target is net area identifiers disagree for intended level 1 adjacency; monitor neighbor adjacency forms at the intended level and LSDB distribution is correct.

Question 121

Two IS-IS routers on a broadcast Ethernet segment repeatedly elect a different DIS. Observed: A maintenance router unexpectedly controls pseudonode LSP generation. Which change most directly corrects the failure while respecting the existing service boundary?

  1. Reassess DIS election behavior and set compatible supported priorities and topology.
  2. Set intended per-level IS-IS DIS priorities consistently across segment participants.
  3. Align repaired link metrics with the approved capacity and latency engineering policy.
  4. Agree on wide metric support across the topology before applying planned link metrics.

Explanation

Correct Answer

B:

The observed condition is A maintenance router unexpectedly controls pseudonode LSP generation. That indicates dis priority and tie-break criteria were not considered in interface design. Applying the proposed remedy directly changes that condition. A concrete completion check is: Pseudonode LSP ownership stabilizes on the approved designated router.

Incorrect Answers

A:

The option may be useful when pseudonode LSPs show a DIS that was administratively expected to be ineligible, but that is not the current evidence. Here, a maintenance router unexpectedly controls pseudonode LSP generation, indicating dis priority and tie-break criteria were not considered in interface design. The targeted action is Set intended per-level IS-IS DIS priorities consistently across segment participants.

C:

This change belongs to a different IS-IS issue: A high-cost path is selected after a fiber repair. That issue involves the remaining interface metric on the repaired circuit is artificially high. The current symptom is A maintenance router unexpectedly controls pseudonode LSP generation. It instead requires set intended per-level IS-IS DIS priorities consistently across segment participants.

D:

This remediates one or more devices retain incompatible metric-style processing, normally indicated by Paths appear with maximum legacy metric rather than engineering cost. It would leave the observed problem (A maintenance router unexpectedly controls pseudonode LSP generation) unresolved. Address it with set intended per-level IS-IS DIS priorities consistently across segment participants.

Question 122

Two IS-IS routers on a broadcast Ethernet segment repeatedly elect a different DIS. Observed: A maintenance router unexpectedly controls pseudonode LSP generation. After the correction, which result would most convincingly show that this fault is resolved?

  1. Pseudonode LSP ownership stabilizes on the approved designated router.
  2. The selected DIS matches supported election rules and operational requirements.
  3. All transit routes use the intended wide metric values with stable SPF outcomes.
  4. SPF again selects the primary path and falls back when its link fails.

Explanation

Correct Answer

A:

After set intended per-level IS-IS DIS priorities consistently across segment participants, inspect whether pseudonode LSP ownership stabilizes on the approved designated router. This closes the loop between the reported observation (A maintenance router unexpectedly controls pseudonode LSP generation) and the underlying issue (DIS priority and tie-break criteria were not considered in interface design).

Incorrect Answers

B:

That observation would verify a separate fault involving is-is dis elections do not use ospf-style zero-priority ineligibility semantics. Its symptom is Pseudonode LSPs show a DIS that was administratively expected to be ineligible. For this case the actual issue is dis priority and tie-break criteria were not considered in interface design, and the relevant success signal is Pseudonode LSP ownership stabilizes on the approved designated router.

C:

This result is useful in another case with evidence Paths appear with maximum legacy metric rather than engineering cost. It does not test recovery from a maintenance router unexpectedly controls pseudonode lsp generation. Check instead whether pseudonode LSP ownership stabilizes on the approved designated router.

D:

It confirms an unrelated service correction: The remaining interface metric on the repaired circuit is artificially high. The present case reports A maintenance router unexpectedly controls pseudonode LSP generation. Its completion test is Pseudonode LSP ownership stabilizes on the approved designated router.

Question 123

Two IS-IS routers on a broadcast Ethernet segment repeatedly elect a different DIS. Observed: A maintenance router unexpectedly controls pseudonode LSP generation. Which root cause is most consistent with this symptom?

  1. The remaining interface metric on the repaired circuit is artificially high.
  2. DIS priority and tie-break criteria were not considered in interface design.
  3. IS-IS DIS elections do not use OSPF-style zero-priority ineligibility semantics.
  4. One or more devices retain incompatible metric-style processing.

Explanation

Correct Answer

B:

The reported evidence—A maintenance router unexpectedly controls pseudonode LSP generation—supports dis priority and tie-break criteria were not considered in interface design. The appropriate intervention is to set intended per-level IS-IS DIS priorities consistently across segment participants, with confirmation from pseudonode LSP ownership stabilizes on the approved designated router. Other causes require actual device-state verification.

Incorrect Answers

A:

The remaining interface metric on the repaired circuit is artificially high. would normally be accompanied by a high-cost path is selected after a fiber repair. The observed symptom is different: A maintenance router unexpectedly controls pseudonode LSP generation. The likely cause is DIS priority and tie-break criteria were not considered in interface design.

C:

The stated cause is possible elsewhere but explains pseudonode lsps show a dis that was administratively expected to be ineligible, not a maintenance router unexpectedly controls pseudonode lsp generation. This incident is better attributed to dis priority and tie-break criteria were not considered in interface design.

D:

That explanation fits another condition: Paths appear with maximum legacy metric rather than engineering cost. The evidence here is A maintenance router unexpectedly controls pseudonode LSP generation. Its closer root cause is DIS priority and tie-break criteria were not considered in interface design.

Question 124

Two IS-IS routers on a broadcast Ethernet segment repeatedly elect a different DIS. Observed: A maintenance router unexpectedly controls pseudonode LSP generation. Which change-acceptance control is most relevant to preventing this exact failure?

  1. For each approved related change, verify that sPF again selects the primary path and falls back when its link fails. Flag recurrence if a high-cost path is selected after a fiber repair.
  2. For each approved related change, verify that pseudonode LSP ownership stabilizes on the approved designated router. Flag recurrence if a maintenance router unexpectedly controls pseudonode LSP generation.
  3. For each approved related change, verify that all transit routes use the intended wide metric values with stable SPF outcomes. Flag recurrence if paths appear with maximum legacy metric rather than engineering cost.
  4. For each approved related change, verify that the selected DIS matches supported election rules and operational requirements. Flag recurrence if pseudonode LSPs show a DIS that was administratively expected to be ineligible.

Explanation

Correct Answer

B:

The control is specific to the initial failure. It requires the result Pseudonode LSP ownership stabilizes on the approved designated router. and treats A maintenance router unexpectedly controls pseudonode LSP generation. as a failure signal. The causal concern is dis priority and tie-break criteria were not considered in interface design.

Incorrect Answers

A:

This gate monitors a different failure, a high-cost path is selected after a fiber repair. It would not detect the current problem: A maintenance router unexpectedly controls pseudonode LSP generation. The appropriate check requires pseudonode LSP ownership stabilizes on the approved designated router.

C:

It is valid for another service scenario but checks paths appear with maximum legacy metric rather than engineering cost. This case instead needs a gate for a maintenance router unexpectedly controls pseudonode lsp generation and evidence that pseudonode LSP ownership stabilizes on the approved designated router.

D:

The proposed control is tied to is-is dis elections do not use ospf-style zero-priority ineligibility semantics, typically observed when pseudonode LSPs show a DIS that was administratively expected to be ineligible. Here the target is dis priority and tie-break criteria were not considered in interface design; monitor pseudonode LSP ownership stabilizes on the approved designated router.

Question 125

A provider migrates from narrow to wide IS-IS metrics. Observed: Paths appear with maximum legacy metric rather than engineering cost. What should the routing engineer change first to address this particular symptom?

  1. Resolve optical instability and use supported SPF and LSP throttling appropriate to the domain.
  2. Add scoped route leaking with compatible up/down protection and routing policy.
  3. Agree on wide metric support across the topology before applying planned link metrics.
  4. Inspect protocol database freshness and forwarding state; perform scoped recovery.

Explanation

Correct Answer

C:

The decisive evidence is that Paths appear with maximum legacy metric rather than engineering cost. This follows from one or more devices retain incompatible metric-style processing. The focused remedy is to agree on wide metric support across the topology before applying planned link metrics. Confirm improvement when all transit routes use the intended wide metric values with stable SPF outcomes. Validate on an approved lab or change window before touching production.

Incorrect Answers

A:

The option may be useful when repeated LSP floods overload route processors across the metro, but that is not the current evidence. Here, paths appear with maximum legacy metric rather than engineering cost, indicating one or more devices retain incompatible metric-style processing. The targeted action is Agree on wide metric support across the topology before applying planned link metrics.

B:

This change belongs to a different IS-IS issue: A Level 1 access router never learns a required remote subnet. That issue involves controlled l2-to-l1 route leaking is not configured for the permitted destination. The current symptom is Paths appear with maximum legacy metric rather than engineering cost. It instead requires agree on wide metric support across the topology before applying planned link metrics.

D:

This remediates spf and forwarding updates have not reconciled with a fresh lsdb after recovery, normally indicated by Neighbors show Up but a route is transiently absent on one PE. It would leave the observed problem (Paths appear with maximum legacy metric rather than engineering cost) unresolved. Address it with agree on wide metric support across the topology before applying planned link metrics.

Question 126

A provider migrates from narrow to wide IS-IS metrics. Observed: Paths appear with maximum legacy metric rather than engineering cost. Which acceptance observation best confirms that the proposed change worked?

  1. All transit routes use the intended wide metric values with stable SPF outcomes.
  2. The allowed prefix reaches Level 1 without route feedback into Level 2.
  3. All devices agree on the LSP sequence and routing destinations become reachable.
  4. LSP churn declines while a legitimate failover still converges promptly.

Explanation

Correct Answer

A:

This acceptance criterion tests the actual fault. The source evidence was Paths appear with maximum legacy metric rather than engineering cost. The correction addresses one or more devices retain incompatible metric-style processing; success requires all transit routes use the intended wide metric values with stable SPF outcomes.

Incorrect Answers

B:

It confirms an unrelated service correction: Controlled L2-to-L1 route leaking is not configured for the permitted destination. The present case reports Paths appear with maximum legacy metric rather than engineering cost. Its completion test is All transit routes use the intended wide metric values with stable SPF outcomes.

C:

This result is useful in another case with evidence Neighbors show Up but a route is transiently absent on one PE. It does not test recovery from paths appear with maximum legacy metric rather than engineering cost. Check instead whether all transit routes use the intended wide metric values with stable SPF outcomes.

D:

That observation would verify a separate fault involving an unstable interface causes repeated topology regenerations and spf scheduling. Its symptom is Repeated LSP floods overload route processors across the metro. For this case the actual issue is one or more devices retain incompatible metric-style processing, and the relevant success signal is All transit routes use the intended wide metric values with stable SPF outcomes.

Question 127

A provider migrates from narrow to wide IS-IS metrics. Observed: Paths appear with maximum legacy metric rather than engineering cost. What is the most likely source of the observed routing or service failure?

  1. Controlled L2-to-L1 route leaking is not configured for the permitted destination.
  2. One or more devices retain incompatible metric-style processing.
  3. SPF and forwarding updates have not reconciled with a fresh LSDB after recovery.
  4. An unstable interface causes repeated topology regenerations and SPF scheduling.

Explanation

Correct Answer

B:

This explanation is the closest match to the observed symptom: Paths appear with maximum legacy metric rather than engineering cost. The specified root issue is One or more devices retain incompatible metric-style processing. Repair it through agree on wide metric support across the topology before applying planned link metrics, then check all transit routes use the intended wide metric values with stable SPF outcomes.

Incorrect Answers

A:

Controlled L2-to-L1 route leaking is not configured for the permitted destination. would normally be accompanied by a level 1 access router never learns a required remote subnet. The observed symptom is different: Paths appear with maximum legacy metric rather than engineering cost. The likely cause is One or more devices retain incompatible metric-style processing.

C:

That explanation fits another condition: Neighbors show Up but a route is transiently absent on one PE. The evidence here is Paths appear with maximum legacy metric rather than engineering cost. Its closer root cause is One or more devices retain incompatible metric-style processing.

D:

The stated cause is possible elsewhere but explains repeated lsp floods overload route processors across the metro, not paths appear with maximum legacy metric rather than engineering cost. This incident is better attributed to one or more devices retain incompatible metric-style processing.

Question 128

A provider migrates from narrow to wide IS-IS metrics. Observed: Paths appear with maximum legacy metric rather than engineering cost. What operational check best guards against this problem returning?

  1. For each approved related change, verify that all transit routes use the intended wide metric values with stable SPF outcomes. Flag recurrence if paths appear with maximum legacy metric rather than engineering cost.
  2. For each approved related change, verify that the allowed prefix reaches Level 1 without route feedback into Level 2. Flag recurrence if a Level 1 access router never learns a required remote subnet.
  3. For each approved related change, verify that lSP churn declines while a legitimate failover still converges promptly. Flag recurrence if repeated LSP floods overload route processors across the metro.
  4. For each approved related change, verify that all devices agree on the LSP sequence and routing destinations become reachable. Flag recurrence if neighbors show Up but a route is transiently absent on one PE.

Explanation

Correct Answer

A:

This control asks for the same recovery evidence (All transit routes use the intended wide metric values with stable SPF outcomes) and flags recurrence of the same failure (Paths appear with maximum legacy metric rather than engineering cost). It targets the underlying issue, one or more devices retain incompatible metric-style processing, rather than a different service problem. The exact cadence must be agreed with operations.

Incorrect Answers

B:

This gate monitors a different failure, a level 1 access router never learns a required remote subnet. It would not detect the current problem: Paths appear with maximum legacy metric rather than engineering cost. The appropriate check requires all transit routes use the intended wide metric values with stable SPF outcomes.

C:

The proposed control is tied to an unstable interface causes repeated topology regenerations and spf scheduling, typically observed when repeated LSP floods overload route processors across the metro. Here the target is one or more devices retain incompatible metric-style processing; monitor all transit routes use the intended wide metric values with stable SPF outcomes.

D:

It is valid for another service scenario but checks neighbors show up but a route is transiently absent on one pe. This case instead needs a gate for paths appear with maximum legacy metric rather than engineering cost and evidence that all transit routes use the intended wide metric values with stable SPF outcomes.

Question 129

An L1/L2 IS-IS PE imports customer prefixes from Level 2. Observed: A Level 1 access router never learns a required remote subnet. Which targeted remediation is most appropriate for the observed condition?

  1. Stage matched IS-IS authentication keys and supported algorithm configuration.
  2. Inspect gateway attached-bit advertisement and set appropriate level-1 metric relationships.
  3. Add scoped route leaking with compatible up/down protection and routing policy.
  4. Assign unique NET system IDs and restart affected adjacencies safely.

Explanation

Correct Answer

C:

This fix addresses the stated cause rather than an unrelated protocol. The reported symptom—A Level 1 access router never learns a required remote subnet—is consistent with controlled l2-to-l1 route leaking is not configured for the permitted destination. Use the specified correction, then verify: The allowed prefix reaches Level 1 without route feedback into Level 2. Preserve existing policy and tenant isolation.

Incorrect Answers

A:

This change belongs to a different IS-IS issue: Adjacencies flap only when authentication is enabled. That issue involves authentication method and key match do not agree between adjacent peers. The current symptom is A Level 1 access router never learns a required remote subnet. It instead requires add scoped route leaking with compatible up/down protection and routing policy.

B:

The option may be useful when traffic consistently uses the farther gateway despite the closer one being healthy, but that is not the current evidence. Here, a Level 1 access router never learns a required remote subnet, indicating controlled l2-to-l1 route leaking is not configured for the permitted destination. The targeted action is Add scoped route leaking with compatible up/down protection and routing policy.

D:

This remediates duplicate is-is system ids cause lsp origin ambiguity, normally indicated by The LSDB shows a second device's LSP under an existing system ID. It would leave the observed problem (A Level 1 access router never learns a required remote subnet) unresolved. Address it with add scoped route leaking with compatible up/down protection and routing policy.

Question 130

An L1/L2 IS-IS PE imports customer prefixes from Level 2. Observed: A Level 1 access router never learns a required remote subnet. What evidence would validate recovery from this precise failure mode?

  1. Neighbors stay up and authentication errors stop in protocol logs.
  2. The allowed prefix reaches Level 1 without route feedback into Level 2.
  3. LSP IDs are unique and topology information becomes stable.
  4. Branch default chooses the planned reachable gateway and avoids unexpected detours.

Explanation

Correct Answer

B:

The intended result is The allowed prefix reaches Level 1 without route feedback into Level 2. It specifically verifies recovery from controlled l2-to-l1 route leaking is not configured for the permitted destination, which produced the original symptom: A Level 1 access router never learns a required remote subnet. It is stronger evidence than a generic interface-up indicator.

Incorrect Answers

A:

It confirms an unrelated service correction: Authentication method and key match do not agree between adjacent peers. The present case reports A Level 1 access router never learns a required remote subnet. Its completion test is The allowed prefix reaches Level 1 without route feedback into Level 2.

C:

This result is useful in another case with evidence The LSDB shows a second device's LSP under an existing system ID. It does not test recovery from a level 1 access router never learns a required remote subnet. Check instead whether the allowed prefix reaches Level 1 without route feedback into Level 2.

D:

That observation would verify a separate fault involving attached-bit and default-cost selection ignore intended internal metric planning. Its symptom is Traffic consistently uses the farther gateway despite the closer one being healthy. For this case the actual issue is controlled l2-to-l1 route leaking is not configured for the permitted destination, and the relevant success signal is The allowed prefix reaches Level 1 without route feedback into Level 2.

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