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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

Questions & Answers

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Juniper JN0-664 Practice Test 77

Question 760

A provider learns an EVPN Type-3 inclusive multicast route. Observed: Broadcast and unknown-unicast traffic never reaches one remote PE. Which change-acceptance control is most relevant to preventing this exact failure?

  1. For each approved related change, verify that bUM traffic reaches each subscribed PE exactly as permitted. Flag recurrence if broadcast and unknown-unicast traffic never reaches one remote PE.
  2. For each approved related change, verify that the L2VPN forwarding map contains one consistent circuit per intended site. Flag recurrence if two attachments map to the same site ID and service endpoints conflict.
  3. For each approved related change, verify that every customer VPLS or circuit includes only its authorized sites. Flag recurrence if a transit PE imports endpoints from an unrelated L2VPN.
  4. For each approved related change, verify that known-unicast forwarding uses qualified paths without persistent duplicate frames. Flag recurrence if both attachment PEs forward duplicate known unicast after migration.

Explanation

Correct Answer

A:

The control is specific to the initial failure. It requires the result BUM traffic reaches each subscribed PE exactly as permitted. and treats Broadcast and unknown-unicast traffic never reaches one remote PE. as a failure signal. The causal concern is the receiving pe lacks an eligible ingress-replication membership or tunnel mapping.

Incorrect Answers

B:

The proposed control is tied to site-id uniqueness is not maintained across the pseudowire service, typically observed when two attachments map to the same site ID and service endpoints conflict. Here the target is the receiving pe lacks an eligible ingress-replication membership or tunnel mapping; monitor bUM traffic reaches each subscribed PE exactly as permitted.

C:

This gate monitors a different failure, a transit pe imports endpoints from an unrelated l2vpn. It would not detect the current problem: Broadcast and unknown-unicast traffic never reaches one remote PE. The appropriate check requires bUM traffic reaches each subscribed PE exactly as permitted.

D:

It is valid for another service scenario but checks both attachment pes forward duplicate known unicast after migration. This case instead needs a gate for broadcast and unknown-unicast traffic never reaches one remote pe and evidence that bUM traffic reaches each subscribed PE exactly as permitted.

Question 761

An EVPN service is migrated from single-homed to all-active customer attachment. Observed: Both attachment PEs forward duplicate known unicast after migration. What should the routing engineer change first to address this particular symptom?

  1. Isolate the offending Layer 2 loop and verify EVPN MAC-mobility state.
  2. Apply the supported active/standby VPLS multihoming policy and test controlled switchover.
  3. Configure supported all-active ES routes and aliasing behavior.
  4. Enable compatible MP-BGP L2VPN family and reflection policy.

Explanation

Correct Answer

C:

The decisive evidence is that Both attachment PEs forward duplicate known unicast after migration. This follows from evpn aliasing and backup-path signaling are not aligned for the ethernet segment. The focused remedy is to configure supported all-active ES routes and aliasing behavior. Confirm improvement when known-unicast forwarding uses qualified paths without persistent duplicate frames. Validate on an approved lab or change window before touching production.

Incorrect Answers

A:

This change belongs to a different Layer 2 VPNs issue: The same customer MAC repeatedly moves without a real host migration. That issue involves duplicate mac origin or loop in the underlying customer ethernet segment. The current symptom is Both attachment PEs forward duplicate known unicast after migration. It instead requires configure supported all-active ES routes and aliasing behavior.

B:

The option may be useful when service recovers briefly then oscillates when the second pseudowire activates, but that is not the current evidence. Here, both attachment PEs forward duplicate known unicast after migration, indicating evpn aliasing and backup-path signaling are not aligned for the ethernet segment. The targeted action is Configure supported all-active ES routes and aliasing behavior.

D:

This remediates the reflector does not negotiate the l2vpn address family for that client, normally indicated by A new spoke receives no Layer 2 VPN membership information. It would leave the observed problem (Both attachment PEs forward duplicate known unicast after migration) unresolved. Address it with configure supported all-active ES routes and aliasing behavior.

Question 762

An EVPN service is migrated from single-homed to all-active customer attachment. Observed: Both attachment PEs forward duplicate known unicast after migration. Which acceptance observation best confirms that the proposed change worked?

  1. MAC movement events settle and forwarding points to the legitimate attachment.
  2. One active attachment forwards at a time and backup takeover is stable.
  3. Authorized L2VPN NLRI reaches the spoke with intact RD and RT information.
  4. Known-unicast forwarding uses qualified paths without persistent duplicate frames.

Explanation

Correct Answer

D:

This acceptance criterion tests the actual fault. The source evidence was Both attachment PEs forward duplicate known unicast after migration. The correction addresses evpn aliasing and backup-path signaling are not aligned for the ethernet segment; success requires known-unicast forwarding uses qualified paths without persistent duplicate frames.

Incorrect Answers

A:

It confirms an unrelated service correction: Duplicate MAC origin or loop in the underlying customer Ethernet segment. The present case reports Both attachment PEs forward duplicate known unicast after migration. Its completion test is Known-unicast forwarding uses qualified paths without persistent duplicate frames.

B:

That observation would verify a separate fault involving multihoming preference and standby pseudowire behavior were not reconciled. Its symptom is Service recovers briefly then oscillates when the second pseudowire activates. For this case the actual issue is evpn aliasing and backup-path signaling are not aligned for the ethernet segment, and the relevant success signal is Known-unicast forwarding uses qualified paths without persistent duplicate frames.

C:

This result is useful in another case with evidence A new spoke receives no Layer 2 VPN membership information. It does not test recovery from both attachment pes forward duplicate known unicast after migration. Check instead whether known-unicast forwarding uses qualified paths without persistent duplicate frames.

Question 763

An EVPN service is migrated from single-homed to all-active customer attachment. Observed: Both attachment PEs forward duplicate known unicast after migration. What is the most likely source of the observed routing or service failure?

  1. EVPN aliasing and backup-path signaling are not aligned for the Ethernet segment.
  2. The reflector does not negotiate the L2VPN address family for that client.
  3. Duplicate MAC origin or loop in the underlying customer Ethernet segment.
  4. Multihoming preference and standby pseudowire behavior were not reconciled.

Explanation

Correct Answer

A:

This explanation is the closest match to the observed symptom: Both attachment PEs forward duplicate known unicast after migration. The specified root issue is EVPN aliasing and backup-path signaling are not aligned for the Ethernet segment. Repair it through configure supported all-active ES routes and aliasing behavior, then check known-unicast forwarding uses qualified paths without persistent duplicate frames.

Incorrect Answers

B:

That explanation fits another condition: A new spoke receives no Layer 2 VPN membership information. The evidence here is Both attachment PEs forward duplicate known unicast after migration. Its closer root cause is EVPN aliasing and backup-path signaling are not aligned for the Ethernet segment.

C:

Duplicate MAC origin or loop in the underlying customer Ethernet segment. would normally be accompanied by the same customer mac repeatedly moves without a real host migration. The observed symptom is different: Both attachment PEs forward duplicate known unicast after migration. The likely cause is EVPN aliasing and backup-path signaling are not aligned for the Ethernet segment.

D:

The stated cause is possible elsewhere but explains service recovers briefly then oscillates when the second pseudowire activates, not both attachment pes forward duplicate known unicast after migration. This incident is better attributed to evpn aliasing and backup-path signaling are not aligned for the ethernet segment.

Question 764

An EVPN service is migrated from single-homed to all-active customer attachment. Observed: Both attachment PEs forward duplicate known unicast after migration. What operational check best guards against this problem returning?

  1. For each approved related change, verify that known-unicast forwarding uses qualified paths without persistent duplicate frames. Flag recurrence if both attachment PEs forward duplicate known unicast after migration.
  2. For each approved related change, verify that one active attachment forwards at a time and backup takeover is stable. Flag recurrence if service recovers briefly then oscillates when the second pseudowire activates.
  3. For each approved related change, verify that authorized L2VPN NLRI reaches the spoke with intact RD and RT information. Flag recurrence if a new spoke receives no Layer 2 VPN membership information.
  4. For each approved related change, verify that mAC movement events settle and forwarding points to the legitimate attachment. Flag recurrence if the same customer MAC repeatedly moves without a real host migration.

Explanation

Correct Answer

A:

This control asks for the same recovery evidence (Known-unicast forwarding uses qualified paths without persistent duplicate frames) and flags recurrence of the same failure (Both attachment PEs forward duplicate known unicast after migration). It targets the underlying issue, evpn aliasing and backup-path signaling are not aligned for the ethernet segment, rather than a different service problem. The exact cadence must be agreed with operations.

Incorrect Answers

B:

The proposed control is tied to multihoming preference and standby pseudowire behavior were not reconciled, typically observed when service recovers briefly then oscillates when the second pseudowire activates. Here the target is evpn aliasing and backup-path signaling are not aligned for the ethernet segment; monitor known-unicast forwarding uses qualified paths without persistent duplicate frames.

C:

It is valid for another service scenario but checks a new spoke receives no layer 2 vpn membership information. This case instead needs a gate for both attachment pes forward duplicate known unicast after migration and evidence that known-unicast forwarding uses qualified paths without persistent duplicate frames.

D:

This gate monitors a different failure, the same customer mac repeatedly moves without a real host migration. It would not detect the current problem: Both attachment PEs forward duplicate known unicast after migration. The appropriate check requires known-unicast forwarding uses qualified paths without persistent duplicate frames.

Question 765

An EVPN PE receives an advertised MAC that flaps between two remote sites. Observed: The same customer MAC repeatedly moves without a real host migration. Which targeted remediation is most appropriate for the observed condition?

  1. Clear stale MAC state safely and update the active VPLS member circuits.
  2. Configure the contracted matching VC ID and compatible circuit signaling on both endpoints.
  3. Isolate the offending Layer 2 loop and verify EVPN MAC-mobility state.
  4. Remove unjustified payload filtering and use proper Ethernet-transparent pseudowire mapping.

Explanation

Correct Answer

C:

This fix addresses the stated cause rather than an unrelated protocol. The reported symptom—The same customer MAC repeatedly moves without a real host migration—is consistent with duplicate mac origin or loop in the underlying customer ethernet segment. Use the specified correction, then verify: MAC movement events settle and forwarding points to the legitimate attachment. Preserve existing policy and tenant isolation.

Incorrect Answers

A:

This change belongs to a different Layer 2 VPNs issue: Customer MAC addresses appear on the wrong PE after a planned move. That issue involves the vpls service still contains stale forwarding database or pseudowire mapping. The current symptom is The same customer MAC repeatedly moves without a real host migration. It instead requires isolate the offending Layer 2 loop and verify EVPN MAC-mobility state.

B:

This remediates the local and remote virtual circuit identifiers do not match, normally indicated by One endpoint reports a matching neighbor but pseudowire status stays Down. It would leave the observed problem (The same customer MAC repeatedly moves without a real host migration) unresolved. Address it with isolate the offending Layer 2 loop and verify EVPN MAC-mobility state.

D:

The option may be useful when iPv6 frames fail while ordinary IPv4 packets cross the same circuit, but that is not the current evidence. Here, the same customer MAC repeatedly moves without a real host migration, indicating duplicate mac origin or loop in the underlying customer ethernet segment. The targeted action is Isolate the offending Layer 2 loop and verify EVPN MAC-mobility state.

Question 766

An EVPN PE receives an advertised MAC that flaps between two remote sites. Observed: The same customer MAC repeatedly moves without a real host migration. What evidence would validate recovery from this precise failure mode?

  1. MAC movement events settle and forwarding points to the legitimate attachment.
  2. Both IPv4 and IPv6 EtherTypes cross according to the customer contract.
  3. The L2 circuit becomes Up and customer frames traverse the pseudowire.
  4. MAC learning associates each CE to the currently correct VPLS attachment.

Explanation

Correct Answer

A:

The intended result is MAC movement events settle and forwarding points to the legitimate attachment. It specifically verifies recovery from duplicate mac origin or loop in the underlying customer ethernet segment, which produced the original symptom: The same customer MAC repeatedly moves without a real host migration. It is stronger evidence than a generic interface-up indicator.

Incorrect Answers

B:

That observation would verify a separate fault involving the service has an inappropriate ethertype filter or nontransparent encapsulation. Its symptom is IPv6 frames fail while ordinary IPv4 packets cross the same circuit. For this case the actual issue is duplicate mac origin or loop in the underlying customer ethernet segment, and the relevant success signal is MAC movement events settle and forwarding points to the legitimate attachment.

C:

This result is useful in another case with evidence One endpoint reports a matching neighbor but pseudowire status stays Down. It does not test recovery from the same customer mac repeatedly moves without a real host migration. Check instead whether mAC movement events settle and forwarding points to the legitimate attachment.

D:

It confirms an unrelated service correction: The VPLS service still contains stale forwarding database or pseudowire mapping. The present case reports The same customer MAC repeatedly moves without a real host migration. Its completion test is MAC movement events settle and forwarding points to the legitimate attachment.

Question 767

An EVPN PE receives an advertised MAC that flaps between two remote sites. Observed: The same customer MAC repeatedly moves without a real host migration. What underlying protocol or service configuration problem best explains the evidence?

  1. The VPLS service still contains stale forwarding database or pseudowire mapping.
  2. Duplicate MAC origin or loop in the underlying customer Ethernet segment.
  3. The service has an inappropriate ethertype filter or nontransparent encapsulation.
  4. The local and remote virtual circuit identifiers do not match.

Explanation

Correct Answer

B:

Because the same customer MAC repeatedly moves without a real host migration, the likely cause is duplicate mac origin or loop in the underlying customer ethernet segment. It is testable: Isolate the offending Layer 2 loop and verify EVPN MAC-mobility state. Expected follow-up: MAC movement events settle and forwarding points to the legitimate attachment.

Incorrect Answers

A:

The VPLS service still contains stale forwarding database or pseudowire mapping. would normally be accompanied by customer mac addresses appear on the wrong pe after a planned move. The observed symptom is different: The same customer MAC repeatedly moves without a real host migration. The likely cause is Duplicate MAC origin or loop in the underlying customer Ethernet segment.

C:

The stated cause is possible elsewhere but explains ipv6 frames fail while ordinary ipv4 packets cross the same circuit, not the same customer mac repeatedly moves without a real host migration. This incident is better attributed to duplicate mac origin or loop in the underlying customer ethernet segment.

D:

That explanation fits another condition: One endpoint reports a matching neighbor but pseudowire status stays Down. The evidence here is The same customer MAC repeatedly moves without a real host migration. Its closer root cause is Duplicate MAC origin or loop in the underlying customer Ethernet segment.

Question 768

An EVPN PE receives an advertised MAC that flaps between two remote sites. Observed: The same customer MAC repeatedly moves without a real host migration. Which ongoing validation gate would best detect a recurrence of this problem?

  1. For each approved related change, verify that mAC movement events settle and forwarding points to the legitimate attachment. Flag recurrence if the same customer MAC repeatedly moves without a real host migration.
  2. For each approved related change, verify that both IPv4 and IPv6 EtherTypes cross according to the customer contract. Flag recurrence if iPv6 frames fail while ordinary IPv4 packets cross the same circuit.
  3. For each approved related change, verify that mAC learning associates each CE to the currently correct VPLS attachment. Flag recurrence if customer MAC addresses appear on the wrong PE after a planned move.
  4. For each approved related change, verify that the L2 circuit becomes Up and customer frames traverse the pseudowire. Flag recurrence if one endpoint reports a matching neighbor but pseudowire status stays Down.

Explanation

Correct Answer

A:

A useful regression gate tests whether mAC movement events settle and forwarding points to the legitimate attachment and alerts when the same customer MAC repeatedly moves without a real host migration. This directly checks the technical weakness: Duplicate MAC origin or loop in the underlying customer Ethernet segment. The gate is derived from the fictional incident and is not an independent Juniper engineer signoff.

Incorrect Answers

B:

The proposed control is tied to the service has an inappropriate ethertype filter or nontransparent encapsulation, typically observed when iPv6 frames fail while ordinary IPv4 packets cross the same circuit. Here the target is duplicate mac origin or loop in the underlying customer ethernet segment; monitor mAC movement events settle and forwarding points to the legitimate attachment.

C:

This gate monitors a different failure, customer mac addresses appear on the wrong pe after a planned move. It would not detect the current problem: The same customer MAC repeatedly moves without a real host migration. The appropriate check requires mAC movement events settle and forwarding points to the legitimate attachment.

D:

It is valid for another service scenario but checks one endpoint reports a matching neighbor but pseudowire status stays down. This case instead needs a gate for the same customer mac repeatedly moves without a real host migration and evidence that mAC movement events settle and forwarding points to the legitimate attachment.

Question 769

A Layer 2 pseudowire carries bridged customer IPv6 traffic. Observed: IPv6 frames fail while ordinary IPv4 packets cross the same circuit. Which change most directly corrects the failure while respecting the existing service boundary?

  1. Remove unjustified payload filtering and use proper Ethernet-transparent pseudowire mapping.
  2. Align service MTU and encapsulation overhead across both pseudowire ends.
  3. Advertise the correct VPLS membership information and import targets.
  4. Align stacked VLAN handling and supported pseudowire encapsulation at both PEs.

Explanation

Correct Answer

A:

The observed condition is IPv6 frames fail while ordinary IPv4 packets cross the same circuit. That indicates the service has an inappropriate ethertype filter or nontransparent encapsulation. Applying the proposed remedy directly changes that condition. A concrete completion check is: Both IPv4 and IPv6 EtherTypes cross according to the customer contract.

Incorrect Answers

B:

This change belongs to a different Layer 2 VPNs issue: Traffic passes small frames but larger customer packets are discarded. That issue involves the attachment circuit and pseudowire do not share a compatible effective mtu. The current symptom is IPv6 frames fail while ordinary IPv4 packets cross the same circuit. It instead requires remove unjustified payload filtering and use proper Ethernet-transparent pseudowire mapping.

C:

The option may be useful when one site never joins the full mesh despite a healthy BGP session, but that is not the current evidence. Here, iPv6 frames fail while ordinary IPv4 packets cross the same circuit, indicating the service has an inappropriate ethertype filter or nontransparent encapsulation. The targeted action is Remove unjustified payload filtering and use proper Ethernet-transparent pseudowire mapping.

D:

This remediates qinq tag handling differs between ingress and remote attachment circuits, normally indicated by Only the outer service VLAN survives and nested customer tags are lost. It would leave the observed problem (IPv6 frames fail while ordinary IPv4 packets cross the same circuit) unresolved. Address it with remove unjustified payload filtering and use proper Ethernet-transparent pseudowire mapping.

Question 770

A Layer 2 pseudowire carries bridged customer IPv6 traffic. Observed: IPv6 frames fail while ordinary IPv4 packets cross the same circuit. After the correction, which result would most convincingly show that this fault is resolved?

  1. Both IPv4 and IPv6 EtherTypes cross according to the customer contract.
  2. Captures at both sites show identical intended inner and outer tag structure.
  3. Large authorized frames pass without fragmentation-induced drops.
  4. All intended remote PEs build their customer VPLS peer connections.

Explanation

Correct Answer

A:

After remove unjustified payload filtering and use proper Ethernet-transparent pseudowire mapping, inspect whether both IPv4 and IPv6 EtherTypes cross according to the customer contract. This closes the loop between the reported observation (IPv6 frames fail while ordinary IPv4 packets cross the same circuit) and the underlying issue (The service has an inappropriate ethertype filter or nontransparent encapsulation).

Incorrect Answers

B:

This result is useful in another case with evidence Only the outer service VLAN survives and nested customer tags are lost. It does not test recovery from ipv6 frames fail while ordinary ipv4 packets cross the same circuit. Check instead whether both IPv4 and IPv6 EtherTypes cross according to the customer contract.

C:

It confirms an unrelated service correction: The attachment circuit and pseudowire do not share a compatible effective MTU. The present case reports IPv6 frames fail while ordinary IPv4 packets cross the same circuit. Its completion test is Both IPv4 and IPv6 EtherTypes cross according to the customer contract.

D:

That observation would verify a separate fault involving the site's vpls nlri or rt export settings are incomplete. Its symptom is One site never joins the full mesh despite a healthy BGP session. For this case the actual issue is the service has an inappropriate ethertype filter or nontransparent encapsulation, and the relevant success signal is Both IPv4 and IPv6 EtherTypes cross according to the customer contract.

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