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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 18

Question 170

An IPv6 IS-IS deployment has working IPv4 reachability. Observed: Routers do not install IPv6 interrouter loopback prefixes. After the correction, which result would most convincingly show that this fault is resolved?

  1. The target IPv6 loopbacks install with correct IS-IS next hops.
  2. No customer-facing IS-IS Hello forms a neighbor while internal routing remains correct.
  3. Neighbor forms at the intended level without padding drops.
  4. Both approved next hops appear with safe load distribution and failover.

Explanation

Correct Answer

A:

After enable supported IS-IS IPv6 reachability on required interfaces and levels, inspect whether the target IPv6 loopbacks install with correct IS-IS next hops. This closes the loop between the reported observation (Routers do not install IPv6 interrouter loopback prefixes) and the underlying issue (IPv6 topology or address-family advertisements are not enabled as intended).

Incorrect Answers

B:

This result is useful in another case with evidence Customer service interface accidentally forms an IS-IS adjacency. It does not test recovery from routers do not install ipv6 interrouter loopback prefixes. Check instead whether the target IPv6 loopbacks install with correct IS-IS next hops.

C:

That observation would verify a separate fault involving is-is hello packet padding exceeds one path's available frame size. Its symptom is Neighbor remains in initialization and three-way handshake does not complete. For this case the actual issue is ipv6 topology or address-family advertisements are not enabled as intended, and the relevant success signal is The target IPv6 loopbacks install with correct IS-IS next hops.

D:

It confirms an unrelated service correction: Wide metrics differ or the installed multipath limit excludes an otherwise equal path. The present case reports Routers do not install IPv6 interrouter loopback prefixes. Its completion test is The target IPv6 loopbacks install with correct IS-IS next hops.

Question 171

An IPv6 IS-IS deployment has working IPv4 reachability. Observed: Routers do not install IPv6 interrouter loopback prefixes. Which root cause is most consistent with this symptom?

  1. IPv6 topology or address-family advertisements are not enabled as intended.
  2. The customer interface was enabled as an active IS-IS circuit instead of a passive advertisement.
  3. Wide metrics differ or the installed multipath limit excludes an otherwise equal path.
  4. IS-IS hello packet padding exceeds one path's available frame size.

Explanation

Correct Answer

A:

The reported evidence—Routers do not install IPv6 interrouter loopback prefixes—supports ipv6 topology or address-family advertisements are not enabled as intended. The appropriate intervention is to enable supported IS-IS IPv6 reachability on required interfaces and levels, with confirmation from the target IPv6 loopbacks install with correct IS-IS next hops. Other causes require actual device-state verification.

Incorrect Answers

B:

That explanation fits another condition: Customer service interface accidentally forms an IS-IS adjacency. The evidence here is Routers do not install IPv6 interrouter loopback prefixes. Its closer root cause is IPv6 topology or address-family advertisements are not enabled as intended.

C:

Wide metrics differ or the installed multipath limit excludes an otherwise equal path. would normally be accompanied by the backup next hop is not in the routing table despite physical path diversity. The observed symptom is different: Routers do not install IPv6 interrouter loopback prefixes. The likely cause is IPv6 topology or address-family advertisements are not enabled as intended.

D:

The stated cause is possible elsewhere but explains neighbor remains in initialization and three-way handshake does not complete, not routers do not install ipv6 interrouter loopback prefixes. This incident is better attributed to ipv6 topology or address-family advertisements are not enabled as intended.

Question 172

An IPv6 IS-IS deployment has working IPv4 reachability. Observed: Routers do not install IPv6 interrouter loopback prefixes. Which change-acceptance control is most relevant to preventing this exact failure?

  1. For each approved related change, verify that neighbor forms at the intended level without padding drops. Flag recurrence if neighbor remains in initialization and three-way handshake does not complete.
  2. For each approved related change, verify that both approved next hops appear with safe load distribution and failover. Flag recurrence if the backup next hop is not in the routing table despite physical path diversity.
  3. For each approved related change, verify that no customer-facing IS-IS Hello forms a neighbor while internal routing remains correct. Flag recurrence if customer service interface accidentally forms an IS-IS adjacency.
  4. For each approved related change, verify that the target IPv6 loopbacks install with correct IS-IS next hops. Flag recurrence if routers do not install IPv6 interrouter loopback prefixes.

Explanation

Correct Answer

D:

The control is specific to the initial failure. It requires the result The target IPv6 loopbacks install with correct IS-IS next hops. and treats Routers do not install IPv6 interrouter loopback prefixes. as a failure signal. The causal concern is ipv6 topology or address-family advertisements are not enabled as intended.

Incorrect Answers

A:

The proposed control is tied to is-is hello packet padding exceeds one path's available frame size, typically observed when neighbor remains in initialization and three-way handshake does not complete. Here the target is ipv6 topology or address-family advertisements are not enabled as intended; monitor the target IPv6 loopbacks install with correct IS-IS next hops.

B:

This gate monitors a different failure, the backup next hop is not in the routing table despite physical path diversity. It would not detect the current problem: Routers do not install IPv6 interrouter loopback prefixes. The appropriate check requires the target IPv6 loopbacks install with correct IS-IS next hops.

C:

It is valid for another service scenario but checks customer service interface accidentally forms an is-is adjacency. This case instead needs a gate for routers do not install ipv6 interrouter loopback prefixes and evidence that the target IPv6 loopbacks install with correct IS-IS next hops.

Question 173

An IS-IS provider core links a customer-facing router with strict route isolation. Observed: Customer service interface accidentally forms an IS-IS adjacency. What should the routing engineer change first to address this particular symptom?

  1. Enable a valid Level 2 topology at the interarea boundary.
  2. Apply deliberate per-interface wide metrics based on the approved TE design.
  3. Compare actual IS-IS Hello fields, circuit type and link MTU to the agreed design.
  4. Make the customer network passive or remove protocol participation as appropriate.

Explanation

Correct Answer

D:

The decisive evidence is that Customer service interface accidentally forms an IS-IS adjacency. This follows from the customer interface was enabled as an active is-is circuit instead of a passive advertisement. The focused remedy is to make the customer network passive or remove protocol participation as appropriate. Confirm improvement when no customer-facing IS-IS Hello forms a neighbor while internal routing remains correct. Validate on an approved lab or change window before touching production.

Incorrect Answers

A:

This remediates a router operates only level 1 across a segment requiring level 2 connectivity, normally indicated by Transit prefixes in one area disappear from an adjacent area. It would leave the observed problem (Customer service interface accidentally forms an IS-IS adjacency) unresolved. Address it with make the customer network passive or remove protocol participation as appropriate.

B:

This change belongs to a different IS-IS issue: Both links receive the same metric despite service quality differences. That issue involves default metrics were left unchanged after the capacity upgrade. The current symptom is Customer service interface accidentally forms an IS-IS adjacency. It instead requires make the customer network passive or remove protocol participation as appropriate.

C:

The option may be useful when the interface receives Hellos but no sustained database synchronization, but that is not the current evidence. Here, customer service interface accidentally forms an IS-IS adjacency, indicating the customer interface was enabled as an active is-is circuit instead of a passive advertisement. The targeted action is Make the customer network passive or remove protocol participation as appropriate.

Question 174

An IS-IS provider core links a customer-facing router with strict route isolation. Observed: Customer service interface accidentally forms an IS-IS adjacency. Which acceptance observation best confirms that the proposed change worked?

  1. The shortest-path result reflects distinct link costs and operational flow validation.
  2. The adjacency reaches Up and LSP flooding completes consistently.
  3. No customer-facing IS-IS Hello forms a neighbor while internal routing remains correct.
  4. Remote Level 2 routes are reachable without improperly merging Level 1 areas.

Explanation

Correct Answer

C:

This acceptance criterion tests the actual fault. The source evidence was Customer service interface accidentally forms an IS-IS adjacency. The correction addresses the customer interface was enabled as an active is-is circuit instead of a passive advertisement; success requires no customer-facing IS-IS Hello forms a neighbor while internal routing remains correct.

Incorrect Answers

A:

It confirms an unrelated service correction: Default metrics were left unchanged after the capacity upgrade. The present case reports Customer service interface accidentally forms an IS-IS adjacency. Its completion test is No customer-facing IS-IS Hello forms a neighbor while internal routing remains correct.

B:

That observation would verify a separate fault involving the peer's link-level settings or level-specific parameters are mismatched. Its symptom is The interface receives Hellos but no sustained database synchronization. For this case the actual issue is the customer interface was enabled as an active is-is circuit instead of a passive advertisement, and the relevant success signal is No customer-facing IS-IS Hello forms a neighbor while internal routing remains correct.

D:

This result is useful in another case with evidence Transit prefixes in one area disappear from an adjacent area. It does not test recovery from customer service interface accidentally forms an is-is adjacency. Check instead whether no customer-facing IS-IS Hello forms a neighbor while internal routing remains correct.

Question 175

An IS-IS provider core links a customer-facing router with strict route isolation. Observed: Customer service interface accidentally forms an IS-IS adjacency. What is the most likely source of the observed routing or service failure?

  1. A router operates only Level 1 across a segment requiring Level 2 connectivity.
  2. The customer interface was enabled as an active IS-IS circuit instead of a passive advertisement.
  3. The peer's link-level settings or level-specific parameters are mismatched.
  4. Default metrics were left unchanged after the capacity upgrade.

Explanation

Correct Answer

B:

This explanation is the closest match to the observed symptom: Customer service interface accidentally forms an IS-IS adjacency. The specified root issue is The customer interface was enabled as an active IS-IS circuit instead of a passive advertisement. Repair it through make the customer network passive or remove protocol participation as appropriate, then check no customer-facing IS-IS Hello forms a neighbor while internal routing remains correct.

Incorrect Answers

A:

That explanation fits another condition: Transit prefixes in one area disappear from an adjacent area. The evidence here is Customer service interface accidentally forms an IS-IS adjacency. Its closer root cause is The customer interface was enabled as an active IS-IS circuit instead of a passive advertisement.

C:

The stated cause is possible elsewhere but explains the interface receives hellos but no sustained database synchronization, not customer service interface accidentally forms an is-is adjacency. This incident is better attributed to the customer interface was enabled as an active is-is circuit instead of a passive advertisement.

D:

Default metrics were left unchanged after the capacity upgrade. would normally be accompanied by both links receive the same metric despite service quality differences. The observed symptom is different: Customer service interface accidentally forms an IS-IS adjacency. The likely cause is The customer interface was enabled as an active IS-IS circuit instead of a passive advertisement.

Question 176

An IS-IS provider core links a customer-facing router with strict route isolation. Observed: Customer service interface accidentally forms an IS-IS adjacency. What operational check best guards against this problem returning?

  1. For each approved related change, verify that remote Level 2 routes are reachable without improperly merging Level 1 areas. Flag recurrence if transit prefixes in one area disappear from an adjacent area.
  2. For each approved related change, verify that the adjacency reaches Up and LSP flooding completes consistently. Flag recurrence if the interface receives Hellos but no sustained database synchronization.
  3. For each approved related change, verify that the shortest-path result reflects distinct link costs and operational flow validation. Flag recurrence if both links receive the same metric despite service quality differences.
  4. For each approved related change, verify that no customer-facing IS-IS Hello forms a neighbor while internal routing remains correct. Flag recurrence if customer service interface accidentally forms an IS-IS adjacency.

Explanation

Correct Answer

D:

This control asks for the same recovery evidence (No customer-facing IS-IS Hello forms a neighbor while internal routing remains correct) and flags recurrence of the same failure (Customer service interface accidentally forms an IS-IS adjacency). It targets the underlying issue, the customer interface was enabled as an active is-is circuit instead of a passive advertisement, 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 transit prefixes in one area disappear from an adjacent area. This case instead needs a gate for customer service interface accidentally forms an is-is adjacency and evidence that no customer-facing IS-IS Hello forms a neighbor while internal routing remains correct.

B:

The proposed control is tied to the peer's link-level settings or level-specific parameters are mismatched, typically observed when the interface receives Hellos but no sustained database synchronization. Here the target is the customer interface was enabled as an active is-is circuit instead of a passive advertisement; monitor no customer-facing IS-IS Hello forms a neighbor while internal routing remains correct.

C:

This gate monitors a different failure, both links receive the same metric despite service quality differences. It would not detect the current problem: Customer service interface accidentally forms an IS-IS adjacency. The appropriate check requires no customer-facing IS-IS Hello forms a neighbor while internal routing remains correct.

Question 177

An IS-IS wide-metric topology has parallel unequal-speed core links. Observed: Both links receive the same metric despite service quality differences. Which targeted remediation is most appropriate for the observed condition?

  1. Add the loopback to the intended IS-IS level without requiring a loopback neighbor.
  2. Restore a legitimate L1/L2 border adjacency and verify attached-bit default propagation.
  3. Apply deliberate per-interface wide metrics based on the approved TE design.
  4. Apply strict route prefix and origin filters and prevent re-redistribution.

Explanation

Correct Answer

C:

This fix addresses the stated cause rather than an unrelated protocol. The reported symptom—Both links receive the same metric despite service quality differences—is consistent with default metrics were left unchanged after the capacity upgrade. Use the specified correction, then verify: The shortest-path result reflects distinct link costs and operational flow validation. Preserve existing policy and tenant isolation.

Incorrect Answers

A:

This change belongs to a different IS-IS issue: The loopback is missing from other routers even though link adjacencies are healthy. That issue involves the intended passive loopback prefix was not advertised in is-is. The current symptom is Both links receive the same metric despite service quality differences. It instead requires apply deliberate per-interface wide metrics based on the approved TE design.

B:

This remediates no attached level 1/level 2 router is advertising the appropriate default path, normally indicated by The device has healthy local adjacencies but does not know any Level 2 exit. It would leave the observed problem (Both links receive the same metric despite service quality differences) unresolved. Address it with apply deliberate per-interface wide metrics based on the approved TE design.

D:

The option may be useful when the route repeatedly returns to the protocol it came from, but that is not the current evidence. Here, both links receive the same metric despite service quality differences, indicating default metrics were left unchanged after the capacity upgrade. The targeted action is Apply deliberate per-interface wide metrics based on the approved TE design.

Question 178

An IS-IS wide-metric topology has parallel unequal-speed core links. Observed: Both links receive the same metric despite service quality differences. What evidence would validate recovery from this precise failure mode?

  1. The shortest-path result reflects distinct link costs and operational flow validation.
  2. The L1 router selects a valid nearest Level 2 exit and customer traffic resumes.
  3. Route origin stays stable across peers and protocol feedback ceases.
  4. Other routers install the loopback and local adjacency state remains unchanged.

Explanation

Correct Answer

A:

The intended result is The shortest-path result reflects distinct link costs and operational flow validation. It specifically verifies recovery from default metrics were left unchanged after the capacity upgrade, which produced the original symptom: Both links receive the same metric despite service quality differences. It is stronger evidence than a generic interface-up indicator.

Incorrect Answers

B:

This result is useful in another case with evidence The device has healthy local adjacencies but does not know any Level 2 exit. It does not test recovery from both links receive the same metric despite service quality differences. Check instead whether the shortest-path result reflects distinct link costs and operational flow validation.

C:

That observation would verify a separate fault involving import and export policy lack route-origin tagging or other feedback suppression. Its symptom is The route repeatedly returns to the protocol it came from. For this case the actual issue is default metrics were left unchanged after the capacity upgrade, and the relevant success signal is The shortest-path result reflects distinct link costs and operational flow validation.

D:

It confirms an unrelated service correction: The intended passive loopback prefix was not advertised in IS-IS. The present case reports Both links receive the same metric despite service quality differences. Its completion test is The shortest-path result reflects distinct link costs and operational flow validation.

Question 179

An IS-IS wide-metric topology has parallel unequal-speed core links. Observed: Both links receive the same metric despite service quality differences. What underlying protocol or service configuration problem best explains the evidence?

  1. No attached Level 1/Level 2 router is advertising the appropriate default path.
  2. The intended passive loopback prefix was not advertised in IS-IS.
  3. Import and export policy lack route-origin tagging or other feedback suppression.
  4. Default metrics were left unchanged after the capacity upgrade.

Explanation

Correct Answer

D:

Because both links receive the same metric despite service quality differences, the likely cause is default metrics were left unchanged after the capacity upgrade. It is testable: Apply deliberate per-interface wide metrics based on the approved TE design. Expected follow-up: The shortest-path result reflects distinct link costs and operational flow validation.

Incorrect Answers

A:

That explanation fits another condition: The device has healthy local adjacencies but does not know any Level 2 exit. The evidence here is Both links receive the same metric despite service quality differences. Its closer root cause is Default metrics were left unchanged after the capacity upgrade.

B:

The intended passive loopback prefix was not advertised in IS-IS. would normally be accompanied by the loopback is missing from other routers even though link adjacencies are healthy. The observed symptom is different: Both links receive the same metric despite service quality differences. The likely cause is Default metrics were left unchanged after the capacity upgrade.

C:

The stated cause is possible elsewhere but explains the route repeatedly returns to the protocol it came from, not both links receive the same metric despite service quality differences. This incident is better attributed to default metrics were left unchanged after the capacity upgrade.

Question 180

An IS-IS wide-metric topology has parallel unequal-speed core links. Observed: Both links receive the same metric despite service quality differences. Which ongoing validation gate would best detect a recurrence of this problem?

  1. For each approved related change, verify that the shortest-path result reflects distinct link costs and operational flow validation. Flag recurrence if both links receive the same metric despite service quality differences.
  2. For each approved related change, verify that the L1 router selects a valid nearest Level 2 exit and customer traffic resumes. Flag recurrence if the device has healthy local adjacencies but does not know any Level 2 exit.
  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 other routers install the loopback and local adjacency state remains unchanged. Flag recurrence if the loopback is missing from other routers even though link adjacencies are healthy.

Explanation

Correct Answer

A:

A useful regression gate tests whether the shortest-path result reflects distinct link costs and operational flow validation and alerts when both links receive the same metric despite service quality differences. This directly checks the technical weakness: Default metrics were left unchanged after the capacity upgrade. 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 the device has healthy local adjacencies but does not know any level 2 exit. This case instead needs a gate for both links receive the same metric despite service quality differences and evidence that the shortest-path result reflects distinct link costs and operational flow validation.

C:

The proposed control is tied to import and export policy lack route-origin tagging or other feedback suppression, typically observed when the route repeatedly returns to the protocol it came from. Here the target is default metrics were left unchanged after the capacity upgrade; monitor the shortest-path result reflects distinct link costs and operational flow validation.

D:

This gate monitors a different failure, the loopback is missing from other routers even though link adjacencies are healthy. It would not detect the current problem: Both links receive the same metric despite service quality differences. The appropriate check requires the shortest-path result reflects distinct link costs and operational flow validation.

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