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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 29

Question 280

An eBGP exchange has a route that the neighbor refuses to accept. Observed: The route appears locally but its next-hop address fails the remote peer's reachability checks. Which change-acceptance control is most relevant to preventing this exact failure?

  1. For each approved related change, verify that all intended iBGP speakers receive the eligible reflected NLRI. Flag recurrence if some nonclient speakers still cannot learn routes from other nonclients.
  2. For each approved related change, verify that remote neighbor installs and forwards through the authorized next hop. Flag recurrence if the route appears locally but its next-hop address fails the remote peer's reachability checks.
  3. For each approved related change, verify that vPNv4 prefixes and their route targets appear at authorized receivers. Flag recurrence if route-monitor output shows no VPNv4 capabilities agreed.
  4. For each approved related change, verify that a valid alternate becomes available during controlled primary route withdrawal. Flag recurrence if another iBGP router receives the path but loses it when the originating client flaps.

Explanation

Correct Answer

B:

The control is specific to the initial failure. It requires the result Remote neighbor installs and forwards through the authorized next hop. and treats The route appears locally but its next-hop address fails the remote peer's reachability checks. as a failure signal. The causal concern is the exported next-hop attribute is inappropriate for the external path.

Incorrect Answers

A:

The proposed control is tied to route reflection only propagates paths according to client and nonclient advertisement rules, typically observed when some nonclient speakers still cannot learn routes from other nonclients. Here the target is the exported next-hop attribute is inappropriate for the external path; monitor remote neighbor installs and forwards through the authorized next hop.

C:

This gate monitors a different failure, route-monitor output shows no vpnv4 capabilities agreed. It would not detect the current problem: The route appears locally but its next-hop address fails the remote peer's reachability checks. The appropriate check requires remote neighbor installs and forwards through the authorized next hop.

D:

It is valid for another service scenario but checks another ibgp router receives the path but loses it when the originating client flaps. This case instead needs a gate for the route appears locally but its next-hop address fails the remote peer's reachability checks and evidence that remote neighbor installs and forwards through the authorized next hop.

Question 281

A route-reflector client sends an external route through an iBGP fabric. Observed: Another iBGP router receives the path but loses it when the originating client flaps. What should the routing engineer change first to address this particular symptom?

  1. Align supported equal-path attributes and multipath settings without hiding real differences.
  2. Restore PE loopback transport visibility without leaking tenant routes into the core.
  3. Design appropriate secondary route visibility or add-path where supported.
  4. Establish a coherent route-reflector cluster identity policy.

Explanation

Correct Answer

C:

The decisive evidence is that Another iBGP router receives the path but loses it when the originating client flaps. This follows from the reflector has no alternate path because add-path or path-diversity strategy is absent. The focused remedy is to design appropriate secondary route visibility or add-path where supported. Confirm improvement when a valid alternate becomes available during controlled primary route withdrawal. Validate on an approved lab or change window before touching production.

Incorrect Answers

A:

This change belongs to a different BGP issue: Only one best next hop is installed even though both sessions advertise the route. That issue involves bgp multipath eligibility criteria or policy are not satisfied. The current symptom is Another iBGP router receives the path but loses it when the originating client flaps. It instead requires design appropriate secondary route visibility or add-path where supported.

B:

The option may be useful when one site receives the route with a next hop it cannot resolve, but that is not the current evidence. Here, another iBGP router receives the path but loses it when the originating client flaps, indicating the reflector has no alternate path because add-path or path-diversity strategy is absent. The targeted action is Design appropriate secondary route visibility or add-path where supported.

D:

This remediates an inconsistent cluster-id configuration creates route-loop prevention mismatches, normally indicated by Clients sporadically reject an otherwise reachable reflected route. It would leave the observed problem (Another iBGP router receives the path but loses it when the originating client flaps) unresolved. Address it with design appropriate secondary route visibility or add-path where supported.

Question 282

A route-reflector client sends an external route through an iBGP fabric. Observed: Another iBGP router receives the path but loses it when the originating client flaps. Which acceptance observation best confirms that the proposed change worked?

  1. A valid alternate becomes available during controlled primary route withdrawal.
  2. Reflected routes carry valid originator and cluster attributes without incorrect rejection.
  3. The VPN prefix resolves to a valid provider transport path.
  4. The route installs both authorized multipath next hops and failover is tested.

Explanation

Correct Answer

A:

This acceptance criterion tests the actual fault. The source evidence was Another iBGP router receives the path but loses it when the originating client flaps. The correction addresses the reflector has no alternate path because add-path or path-diversity strategy is absent; success requires a valid alternate becomes available during controlled primary route withdrawal.

Incorrect Answers

B:

This result is useful in another case with evidence Clients sporadically reject an otherwise reachable reflected route. It does not test recovery from another ibgp router receives the path but loses it when the originating client flaps. Check instead whether a valid alternate becomes available during controlled primary route withdrawal.

C:

That observation would verify a separate fault involving pe loopback reachability is missing from the transport igp. Its symptom is One site receives the route with a next hop it cannot resolve. For this case the actual issue is the reflector has no alternate path because add-path or path-diversity strategy is absent, and the relevant success signal is A valid alternate becomes available during controlled primary route withdrawal.

D:

It confirms an unrelated service correction: BGP multipath eligibility criteria or policy are not satisfied. The present case reports Another iBGP router receives the path but loses it when the originating client flaps. Its completion test is A valid alternate becomes available during controlled primary route withdrawal.

Question 283

A route-reflector client sends an external route through an iBGP fabric. Observed: Another iBGP router receives the path but loses it when the originating client flaps. What is the most likely source of the observed routing or service failure?

  1. The reflector has no alternate path because add-path or path-diversity strategy is absent.
  2. An inconsistent cluster-ID configuration creates route-loop prevention mismatches.
  3. BGP multipath eligibility criteria or policy are not satisfied.
  4. PE loopback reachability is missing from the transport IGP.

Explanation

Correct Answer

A:

This explanation is the closest match to the observed symptom: Another iBGP router receives the path but loses it when the originating client flaps. The specified root issue is The reflector has no alternate path because add-path or path-diversity strategy is absent. Repair it through design appropriate secondary route visibility or add-path where supported, then check a valid alternate becomes available during controlled primary route withdrawal.

Incorrect Answers

B:

That explanation fits another condition: Clients sporadically reject an otherwise reachable reflected route. The evidence here is Another iBGP router receives the path but loses it when the originating client flaps. Its closer root cause is The reflector has no alternate path because add-path or path-diversity strategy is absent.

C:

BGP multipath eligibility criteria or policy are not satisfied. would normally be accompanied by only one best next hop is installed even though both sessions advertise the route. The observed symptom is different: Another iBGP router receives the path but loses it when the originating client flaps. The likely cause is The reflector has no alternate path because add-path or path-diversity strategy is absent.

D:

The stated cause is possible elsewhere but explains one site receives the route with a next hop it cannot resolve, not another ibgp router receives the path but loses it when the originating client flaps. This incident is better attributed to the reflector has no alternate path because add-path or path-diversity strategy is absent.

Question 284

A route-reflector client sends an external route through an iBGP fabric. Observed: Another iBGP router receives the path but loses it when the originating client flaps. What operational check best guards against this problem returning?

  1. For each approved related change, verify that reflected routes carry valid originator and cluster attributes without incorrect rejection. Flag recurrence if clients sporadically reject an otherwise reachable reflected route.
  2. For each approved related change, verify that the VPN prefix resolves to a valid provider transport path. Flag recurrence if one site receives the route with a next hop it cannot resolve.
  3. For each approved related change, verify that a valid alternate becomes available during controlled primary route withdrawal. Flag recurrence if another iBGP router receives the path but loses it when the originating client flaps.
  4. For each approved related change, verify that the route installs both authorized multipath next hops and failover is tested. Flag recurrence if only one best next hop is installed even though both sessions advertise the route.

Explanation

Correct Answer

C:

This control asks for the same recovery evidence (A valid alternate becomes available during controlled primary route withdrawal) and flags recurrence of the same failure (Another iBGP router receives the path but loses it when the originating client flaps). It targets the underlying issue, the reflector has no alternate path because add-path or path-diversity strategy is absent, 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 clients sporadically reject an otherwise reachable reflected route. This case instead needs a gate for another ibgp router receives the path but loses it when the originating client flaps and evidence that a valid alternate becomes available during controlled primary route withdrawal.

B:

The proposed control is tied to pe loopback reachability is missing from the transport igp, typically observed when one site receives the route with a next hop it cannot resolve. Here the target is the reflector has no alternate path because add-path or path-diversity strategy is absent; monitor a valid alternate becomes available during controlled primary route withdrawal.

D:

This gate monitors a different failure, only one best next hop is installed even though both sessions advertise the route. It would not detect the current problem: Another iBGP router receives the path but loses it when the originating client flaps. The appropriate check requires a valid alternate becomes available during controlled primary route withdrawal.

Question 285

An edge uses BGP multipath toward two equivalent upstream neighbors. Observed: Only one best next hop is installed even though both sessions advertise the route. Which targeted remediation is most appropriate for the observed condition?

  1. Repair IGP reachability or apply an appropriate next-hop-self policy at the ingress border.
  2. Align supported equal-path attributes and multipath settings without hiding real differences.
  3. Examine damping state and adjust the policy to approved convergence objectives.
  4. Check four-octet capability negotiation and parse AS4 attributes correctly.

Explanation

Correct Answer

B:

This fix addresses the stated cause rather than an unrelated protocol. The reported symptom—Only one best next hop is installed even though both sessions advertise the route—is consistent with bgp multipath eligibility criteria or policy are not satisfied. Use the specified correction, then verify: The route installs both authorized multipath next hops and failover is tested. Preserve existing policy and tenant isolation.

Incorrect Answers

A:

This change belongs to a different BGP issue: Peers see the advertised prefix but cannot install it in their RIBs. That issue involves the advertised bgp next hop is unreachable in the underlay. The current symptom is Only one best next hop is installed even though both sessions advertise the route. It instead requires align supported equal-path attributes and multipath settings without hiding real differences.

C:

The option may be useful when a stable recovered prefix stays suppressed after several route updates, but that is not the current evidence. Here, only one best next hop is installed even though both sessions advertise the route, indicating bgp multipath eligibility criteria or policy are not satisfied. The targeted action is Align supported equal-path attributes and multipath settings without hiding real differences.

D:

This remediates four-octet as capability handling is being read as an actual unexpected transit asn, normally indicated by A monitoring system reports AS_TRANS unexpectedly in the legacy view. It would leave the observed problem (Only one best next hop is installed even though both sessions advertise the route) unresolved. Address it with align supported equal-path attributes and multipath settings without hiding real differences.

Question 286

An edge uses BGP multipath toward two equivalent upstream neighbors. Observed: Only one best next hop is installed even though both sessions advertise the route. What evidence would validate recovery from this precise failure mode?

  1. Both peers display the intended full AS numbers and routes retain valid AS paths.
  2. The prefix becomes active with a resolvable BGP next hop.
  3. The route installs both authorized multipath next hops and failover is tested.
  4. The recovered prefix becomes usable after permitted penalty decay without excessive flapping.

Explanation

Correct Answer

C:

The intended result is The route installs both authorized multipath next hops and failover is tested. It specifically verifies recovery from bgp multipath eligibility criteria or policy are not satisfied, which produced the original symptom: Only one best next hop is installed even though both sessions advertise the route. It is stronger evidence than a generic interface-up indicator.

Incorrect Answers

A:

This result is useful in another case with evidence A monitoring system reports AS_TRANS unexpectedly in the legacy view. It does not test recovery from only one best next hop is installed even though both sessions advertise the route. Check instead whether the route installs both authorized multipath next hops and failover is tested.

B:

It confirms an unrelated service correction: The advertised BGP next hop is unreachable in the underlay. The present case reports Only one best next hop is installed even though both sessions advertise the route. Its completion test is The route installs both authorized multipath next hops and failover is tested.

D:

That observation would verify a separate fault involving route flap damping penalty and reuse thresholds remain active. Its symptom is A stable recovered prefix stays suppressed after several route updates. For this case the actual issue is bgp multipath eligibility criteria or policy are not satisfied, and the relevant success signal is The route installs both authorized multipath next hops and failover is tested.

Question 287

An edge uses BGP multipath toward two equivalent upstream neighbors. Observed: Only one best next hop is installed even though both sessions advertise the route. What underlying protocol or service configuration problem best explains the evidence?

  1. BGP multipath eligibility criteria or policy are not satisfied.
  2. The advertised BGP next hop is unreachable in the underlay.
  3. Four-octet AS capability handling is being read as an actual unexpected transit ASN.
  4. Route flap damping penalty and reuse thresholds remain active.

Explanation

Correct Answer

A:

Because only one best next hop is installed even though both sessions advertise the route, the likely cause is bgp multipath eligibility criteria or policy are not satisfied. It is testable: Align supported equal-path attributes and multipath settings without hiding real differences. Expected follow-up: The route installs both authorized multipath next hops and failover is tested.

Incorrect Answers

B:

The advertised BGP next hop is unreachable in the underlay. would normally be accompanied by peers see the advertised prefix but cannot install it in their ribs. The observed symptom is different: Only one best next hop is installed even though both sessions advertise the route. The likely cause is BGP multipath eligibility criteria or policy are not satisfied.

C:

That explanation fits another condition: A monitoring system reports AS_TRANS unexpectedly in the legacy view. The evidence here is Only one best next hop is installed even though both sessions advertise the route. Its closer root cause is BGP multipath eligibility criteria or policy are not satisfied.

D:

The stated cause is possible elsewhere but explains a stable recovered prefix stays suppressed after several route updates, not only one best next hop is installed even though both sessions advertise the route. This incident is better attributed to bgp multipath eligibility criteria or policy are not satisfied.

Question 288

An edge uses BGP multipath toward two equivalent upstream neighbors. Observed: Only one best next hop is installed even though both sessions advertise the route. Which ongoing validation gate would best detect a recurrence of this problem?

  1. For each approved related change, verify that the route installs both authorized multipath next hops and failover is tested. Flag recurrence if only one best next hop is installed even though both sessions advertise the route.
  2. For each approved related change, verify that the prefix becomes active with a resolvable BGP next hop. Flag recurrence if peers see the advertised prefix but cannot install it in their RIBs.
  3. For each approved related change, verify that both peers display the intended full AS numbers and routes retain valid AS paths. Flag recurrence if a monitoring system reports AS_TRANS unexpectedly in the legacy view.
  4. For each approved related change, verify that the recovered prefix becomes usable after permitted penalty decay without excessive flapping. Flag recurrence if a stable recovered prefix stays suppressed after several route updates.

Explanation

Correct Answer

A:

A useful regression gate tests whether the route installs both authorized multipath next hops and failover is tested and alerts when only one best next hop is installed even though both sessions advertise the route. This directly checks the technical weakness: BGP multipath eligibility criteria or policy are not satisfied. The gate is derived from the fictional incident and is not an independent Juniper engineer signoff.

Incorrect Answers

B:

This gate monitors a different failure, peers see the advertised prefix but cannot install it in their ribs. It would not detect the current problem: Only one best next hop is installed even though both sessions advertise the route. The appropriate check requires the route installs both authorized multipath next hops and failover is tested.

C:

It is valid for another service scenario but checks a monitoring system reports as_trans unexpectedly in the legacy view. This case instead needs a gate for only one best next hop is installed even though both sessions advertise the route and evidence that the route installs both authorized multipath next hops and failover is tested.

D:

The proposed control is tied to route flap damping penalty and reuse thresholds remain active, typically observed when a stable recovered prefix stays suppressed after several route updates. Here the target is bgp multipath eligibility criteria or policy are not satisfied; monitor the route installs both authorized multipath next hops and failover is tested.

Question 289

A provider uses route damping on a customer aggregate. Observed: A stable recovered prefix stays suppressed after several route updates. Which change most directly corrects the failure while respecting the existing service boundary?

  1. Correct scoped policy ordering and community match before route installation.
  2. Correct import policy local preference consistently within the local AS.
  3. Establish permitted FlowSpec family and validation rules before accepting actions.
  4. Examine damping state and adjust the policy to approved convergence objectives.

Explanation

Correct Answer

D:

The observed condition is A stable recovered prefix stays suppressed after several route updates. That indicates route flap damping penalty and reuse thresholds remain active. Applying the proposed remedy directly changes that condition. A concrete completion check is: The recovered prefix becomes usable after permitted penalty decay without excessive flapping.

Incorrect Answers

A:

This change belongs to a different BGP issue: A route arrives with the right community but enters the wrong routing instance. That issue involves the policy term matches community yet assigns an unintended routing-instance action. The current symptom is A stable recovered prefix stays suppressed after several route updates. It instead requires examine damping state and adjust the policy to approved convergence objectives.

B:

The option may be useful when traffic selects an unwanted exit despite the closer contracted carrier, but that is not the current evidence. Here, a stable recovered prefix stays suppressed after several route updates, indicating route flap damping penalty and reuse thresholds remain active. The targeted action is Examine damping state and adjust the policy to approved convergence objectives.

C:

This remediates flowspec address-family negotiation or validation against unicast reachability fails, normally indicated by A FlowSpec announcement is present but the PE never applies the firewall action. It would leave the observed problem (A stable recovered prefix stays suppressed after several route updates) unresolved. Address it with examine damping state and adjust the policy to approved convergence objectives.

Question 290

A provider uses route damping on a customer aggregate. Observed: A stable recovered prefix stays suppressed after several route updates. After the correction, which result would most convincingly show that this fault is resolved?

  1. Only authorized mitigation components are programmed in the forwarding plane.
  2. The permitted tagged route enters only the intended instance.
  3. The best path selects the approved egress without modifying remote providers.
  4. The recovered prefix becomes usable after permitted penalty decay without excessive flapping.

Explanation

Correct Answer

D:

After examine damping state and adjust the policy to approved convergence objectives, inspect whether the recovered prefix becomes usable after permitted penalty decay without excessive flapping. This closes the loop between the reported observation (A stable recovered prefix stays suppressed after several route updates) and the underlying issue (Route flap damping penalty and reuse thresholds remain active).

Incorrect Answers

A:

This result is useful in another case with evidence A FlowSpec announcement is present but the PE never applies the firewall action. It does not test recovery from a stable recovered prefix stays suppressed after several route updates. Check instead whether the recovered prefix becomes usable after permitted penalty decay without excessive flapping.

B:

It confirms an unrelated service correction: The policy term matches community yet assigns an unintended routing-instance action. The present case reports A stable recovered prefix stays suppressed after several route updates. Its completion test is The recovered prefix becomes usable after permitted penalty decay without excessive flapping.

C:

That observation would verify a separate fault involving local preference policy unintentionally favors the expensive upstream path. Its symptom is Traffic selects an unwanted exit despite the closer contracted carrier. For this case the actual issue is route flap damping penalty and reuse thresholds remain active, and the relevant success signal is The recovered prefix becomes usable after permitted penalty decay without excessive flapping.

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