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Exam Code: JN0-364

Exam Name: Service Provider Routing and Switching, Specialist (JNCIS-SP)

Certification Provider: Juniper

Questions & Answers

Juniper JN0-364 Questions & Answers

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"Service Provider Routing and Switching, Specialist (JNCIS-SP) Exam", also known as JN0-364 exam, is a Juniper certification exam.

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Juniper JN0-364 Practice Test 40

Question 390

A fictional service-provider team at Brookstone Communications is reviewing a wholesale access handoff. The finding is: A provider access fabric changes its MST revision on only one device and behaves like a boundary instead of a single region. Which ongoing control would most directly detect or prevent the same failure from recurring?

  1. Monitor root-bridge identity and test controlled superior-BPDU attempts at trust boundaries.
  2. Audit VSTP per-VLAN root topology after new VLAN or trunk additions.
  3. Validate MST digest and instance mapping consistency as part of configuration review.
  4. Audit network type against actual link topology during edge circuit deployment.

Explanation

Correct Answer

C:

Validate MST digest and instance mapping consistency as part of configuration review. This monitors the behavior that failed at Brookstone Communications; the most useful acceptance signal is that adjacent devices report matching MST region configuration and VLANs map to the same intended instances.

Incorrect Answers

A:

The control protects RSTP root protection. It does not establish the ongoing MSTP region consistency behavior required in this network. MSTP region identity depends on consistent name, revision, and VLAN mapping; mismatches create region boundaries.

B:

This is a useful guard against VSTP per-VLAN root choice, but it is not scoped to the observed MSTP region consistency failure. An appropriate test would show that adjacent devices report matching MST region configuration and VLANs map to the same intended instances.

D:

Audit network type against actual link topology during edge circuit deployment. The monitored boundary differs from MSTP region consistency, so the original weakness might reappear unnoticed. MSTP region identity depends on consistent name, revision, and VLAN mapping; mismatches create region boundaries.

Question 391

The operations group at fictional Sprucewell Transit, working on a dual-stack transit pilot, finds: After a core migration, a node SID is missing from the IGP advertisement and ingress nodes cannot build the intended SR-MPLS path. Which ongoing control would most directly detect or prevent the same failure from recurring?

  1. Compare intended LDP interface coverage against active discovery neighbors after link additions.
  2. Validate node-SID uniqueness, advertised SRGB ranges and effective label forwarding after upgrades.
  3. Audit MPLS forwarding tables and labeled traffic counters after routing or hardware transitions.
  4. Audit the RIB group import targets and confirm that only approved prefixes are duplicated across tables.

Explanation

Correct Answer

B:

Validate node-SID uniqueness, advertised SRGB ranges and effective label forwarding after upgrades. This monitors the behavior that failed at Sprucewell Transit; the most useful acceptance signal is that the prefix SID is advertised and all ingress routers compute consistent transport label behavior for the node destination.

Incorrect Answers

A:

Compare intended LDP interface coverage against active discovery neighbors after link additions. The monitored boundary differs from segment routing prefix SID, so the original weakness might reappear unnoticed. SR-MPLS prefix SIDs and the segment routing global block provide IGP-signaled reachability without relying on LDP for each FEC.

C:

Audit MPLS forwarding tables and labeled traffic counters after routing or hardware transitions. The monitored boundary differs from segment routing prefix SID, so the original weakness might reappear unnoticed. SR-MPLS prefix SIDs and the segment routing global block provide IGP-signaled reachability without relying on LDP for each FEC.

D:

Audit the RIB group import targets and confirm that only approved prefixes are duplicated across tables. The monitored boundary differs from segment routing prefix SID, so the original weakness might reappear unnoticed. SR-MPLS prefix SIDs and the segment routing global block provide IGP-signaled reachability without relying on LDP for each FEC.

Question 392

At fictional Juniper Glen Telecom, during a backbone recovery drill, engineers report: A failed root-facing link causes a long outage because the team mistakes an alternate port for a disabled edge and never validates its role. Which focused engineering action would best correct the fault?

  1. Set compatible IS-IS circuit levels on both ends of the interface and verify hello and neighbor state.
  2. Use loop protection on appropriate nondesignated interfaces and verify the safe state during missing-BPDU events.
  3. Configure and verify the intended VSTP instance and per-VLAN root priorities for the affected VLANs.
  4. Review RSTP roles and convergence expectations and ensure the valid alternate path can transition safely when the root path fails.

Explanation

Correct Answer

D:

Review RSTP roles and convergence expectations and ensure the valid alternate path can transition safely when the root path fails. This treats the fault shown by Juniper Glen Telecom: RSTP port roles and rapid state transitions support fast loop-free reconvergence, unlike simply forcing all redundant ports forwarding. Confirm success when the alternate port assumes an appropriate forwarding role on failure without allowing simultaneous Layer 2 loops.

Incorrect Answers

A:

Set compatible IS-IS circuit levels on both ends of the interface and verify hello and neighbor state. Its normal acceptance signal would be the expected L1 or L2 IS-IS adjacency appears and routing information for the selected level is exchanged. Here the deciding check is different: the alternate port assumes an appropriate forwarding role on failure without allowing simultaneous Layer 2 loops.

B:

Use loop protection on appropriate nondesignated interfaces and verify the safe state during missing-BPDU events. Its normal acceptance signal would be the impacted non-designated port stays protected while BPDUs are absent and returns only after control-plane health is restored. Here the deciding check is different: the alternate port assumes an appropriate forwarding role on failure without allowing simultaneous Layer 2 loops.

C:

Configure and verify the intended VSTP instance and per-VLAN root priorities for the affected VLANs. This addresses VSTP per-VLAN root choice, but the reported symptoms arise from RSTP alternate port reconvergence. For this case, verify instead that the alternate port assumes an appropriate forwarding role on failure without allowing simultaneous Layer 2 loops.

Question 393

During a carrier peering cutover at fictional Riverbend Exchange, the team observes: A backbone router carries Level 2 topology yet an adjacent Level 1-only router cannot select an inter-area route through the planned L1-L2 border. Which networking principle most accurately explains the observed failure?

  1. IS-IS uses TLVs inside its PDUs to encode prefix and protocol capabilities; adjacency alone is not proof of expected reachability advertisements.
  2. IS-IS peers must support a common adjacency level; active Ethernet transport does not compensate for a level mismatch.
  3. Penultimate-hop popping can remove an outer transport label before the egress, reducing egress label processing.
  4. IS-IS uses Level 1 within an area and Level 2 between areas; an L1 router needs an appropriate inter-area exit or route leak.

Explanation

Correct Answer

D:

IS-IS uses Level 1 within an area and Level 2 between areas; an L1 router needs an appropriate inter-area exit or route leak. That is the specific distinction behind the observed outage. The targeted fix is to ensure a healthy Level 1–Level 2 boundary and appropriate reachable exit or leaked route for the remote destination.

Incorrect Answers

A:

IS-IS uses TLVs inside its PDUs to encode prefix and protocol capabilities; adjacency alone is not proof of expected reachability advertisements. That describes IS-IS TLV reachability, whereas the observed symptoms are caused by IS-IS L1 and L2 reachability; it does not predict the reported behavior.

B:

IS-IS peers must support a common adjacency level; active Ethernet transport does not compensate for a level mismatch. That describes IS-IS adjacency circuit level, whereas the observed symptoms are caused by IS-IS L1 and L2 reachability; it does not predict the reported behavior.

C:

Although penultimate hop popping needs this consideration, the failure at issue has a different cause. IS-IS uses Level 1 within an area and Level 2 between areas; an L1 router needs an appropriate inter-area exit or route leak.

Question 394

A fictional service-provider team at Foxglove Broadband is reviewing a provider-edge service migration. The finding is: Two trunk endpoints disagree on where untagged control traffic belongs, placing frames in the wrong customer VLAN. Which observation would most directly establish that the reported failure has been repaired?

  1. Untagged frames map to the intended VLAN on both devices while explicitly tagged VLAN traffic remains isolated.
  2. Captured service frames show the expected outer provider tag and unchanged customer tag, with distinct customers isolated.
  3. Hosts reach the expected IRB gateway and traffic between approved subnets is routed rather than bridged blindly.
  4. Neighbor state and system IDs show unique routers, and Level 1 adjacency establishes only among compatible area peers.

Explanation

Correct Answer

A:

Untagged frames map to the intended VLAN on both devices while explicitly tagged VLAN traffic remains isolated. It tests the failed behavior itself rather than merely confirming that a configuration was committed. A native VLAN determines how untagged frames are classified on a trunk; inconsistent native mappings can silently bridge the wrong domain.

Incorrect Answers

B:

The check is meaningful for provider Q-in-Q tagging, but it does not prove that native untagged VLAN drift was repaired. A native VLAN determines how untagged frames are classified on a trunk; inconsistent native mappings can silently bridge the wrong domain.

C:

Hosts reach the expected IRB gateway and traffic between approved subnets is routed rather than bridged blindly. That establishes integrated routing and bridging rather than a repaired native untagged VLAN drift path. The reported failure still requires this evidence: untagged frames map to the intended VLAN on both devices while explicitly tagged VLAN traffic remains isolated.

D:

This measurement tests IS-IS NET and system ID; it cannot distinguish success from failure for the observed native untagged VLAN drift condition. A native VLAN determines how untagged frames are classified on a trunk; inconsistent native mappings can silently bridge the wrong domain.

Question 395

The operations group at fictional Seabright Networks, working on a network change window, finds: A route to the GRE destination is accidentally learned through the GRE tunnel itself, making the tunnel recursively depend on its own forwarding. Which ongoing control would most directly detect or prevent the same failure from recurring?

  1. Test tunnel path MTU and fragmentation behavior with realistic payload sizes after transport changes.
  2. Validate next-hop address scope and outbound interface for static IPv6 routes during deployment.
  3. Review tunnel transport security requirements and verify encryption rather than accepting GRE setup as proof of privacy.
  4. Guard tunnel outer endpoint routes against redistribution into the overlay routing table.

Explanation

Correct Answer

D:

Guard tunnel outer endpoint routes against redistribution into the overlay routing table. This monitors the behavior that failed at Seabright Networks; the most useful acceptance signal is that the outer GRE endpoint resolves to an underlay interface while only intended inner destinations use the tunnel.

Incorrect Answers

A:

The control protects GRE tunnel path MTU. It does not establish the ongoing GRE recursive route avoidance behavior required in this network. A tunnel's transport destination must not depend on routing through that same tunnel; recursion defeats the encapsulation path.

B:

The control protects IPv6 static next-hop scope. It does not establish the ongoing GRE recursive route avoidance behavior required in this network. A tunnel's transport destination must not depend on routing through that same tunnel; recursion defeats the encapsulation path.

C:

Review tunnel transport security requirements and verify encryption rather than accepting GRE setup as proof of privacy. That ongoing check is for GRE confidentiality limitation; it would not reliably detect recurrence of GRE recursive route avoidance. A tunnel's transport destination must not depend on routing through that same tunnel; recursion defeats the encapsulation path.

Question 396

At fictional Unionpoint Mobile, during a wholesale access handoff, engineers report: A route reflector delivers customer prefixes successfully yet forwarding fails because downstream routers cannot resolve the advertised border next hop. Which networking principle most accurately explains the observed failure?

  1. AS-path prepending can make a path less attractive to other ASes but does not override their local policies or guarantee inbound steering.
  2. A BGP path is not usable merely because UPDATE is received; next-hop resolution is required for route selection and installation.
  3. OSPF area identity is part of neighbor compatibility, and mismatched area membership prevents formation of the intended adjacency.
  4. LOCAL_PREF is an intradomain BGP path attribute that normally influences preferred outbound exit for routes inside the AS.

Explanation

Correct Answer

B:

A BGP path is not usable merely because UPDATE is received; next-hop resolution is required for route selection and installation. That is the specific distinction behind the observed outage. The targeted fix is to fix internal next-hop reachability or use appropriate next-hop handling on the egress boundary, then confirm usable BGP forwarding. Applied here, the relevant facts are: A route reflector delivers customer prefixes successfully yet forwarding fails because downstream routers cannot resolve the advertised border next hop. The question asks which networking principle most accurately explains the observed failure.

Incorrect Answers

A:

AS-path prepending can make a path less attractive to other ASes but does not override their local policies or guarantee inbound steering. Those conditions do not account for the specific BGP next-hop reachability problem reported by Unionpoint Mobile.

C:

OSPF area identity is part of neighbor compatibility, and mismatched area membership prevents formation of the intended adjacency. Those conditions do not account for the specific BGP next-hop reachability problem reported by Unionpoint Mobile.

D:

LOCAL_PREF is an intradomain BGP path attribute that normally influences preferred outbound exit for routes inside the AS. That describes BGP local preference, whereas the observed symptoms are caused by BGP next-hop reachability; it does not predict the reported behavior.

Question 397

During a regional backbone upgrade at fictional Seabright Networks, the team observes: Two OSPF exits both converge but a high-capacity core path loses because the configured cumulative costs favor a slower path. Which networking principle most accurately explains the observed failure?

  1. OSPF point-to-point interfaces do not use a DR or BDR; this differs from a shared multiaccess Ethernet network.
  2. OSPF chooses lowest-cost paths computed from link-state topology; a Full adjacency alone does not guarantee the desired route preference.
  3. OSPF uses the router ID to identify LSA originators; duplicate or unstable IDs undermine link-state identity.
  4. Edge BPDU protection is intended for ports expected to connect to hosts, not for ordinary switch-to-switch links that exchange BPDUs.

Explanation

Correct Answer

B:

OSPF chooses lowest-cost paths computed from link-state topology; a Full adjacency alone does not guarantee the desired route preference. That is the specific distinction behind the observed outage. The targeted fix is to tune the intended OSPF interface costs and verify SPF-selected reachability for the affected destinations. Applied here, the relevant facts are: Two OSPF exits both converge but a high-capacity core path loses because the configured cumulative costs favor a slower path. The question asks which networking principle most accurately explains the observed failure.

Incorrect Answers

A:

OSPF point-to-point interfaces do not use a DR or BDR; this differs from a shared multiaccess Ethernet network. Those conditions do not account for the specific OSPF interface metric selection problem reported by Seabright Networks.

C:

This principle matters when troubleshooting stable OSPF router identifier, but using it here mistakes a different failure mode for OSPF interface metric selection. The relevant distinction is: OSPF chooses lowest-cost paths computed from link-state topology; a Full adjacency alone does not guarantee the desired route preference.

D:

Edge BPDU protection is intended for ports expected to connect to hosts, not for ordinary switch-to-switch links that exchange BPDUs. Those conditions do not account for the specific OSPF interface metric selection problem reported by Seabright Networks.

Question 398

A fictional service-provider team at Ridgefield Carrier is reviewing a network change window. The finding is: Following a provider transport swap, OSPF hellos continue but database description exchange stalls where the advertised MTUs differ. Which focused engineering action would best correct the fault?

  1. Resolve the underlying link MTU mismatch and validate successful database description exchange rather than masking the check.
  2. Set compatible IS-IS circuit levels on both ends of the interface and verify hello and neighbor state.
  3. Apply a scoped OSPF export policy to originate only the approved active source prefix and confirm the receiving routers learn it.
  4. Review interface network type and DR priorities, then plan election behavior with the existing DR and BDR state in mind.

Explanation

Correct Answer

A:

Resolve the underlying link MTU mismatch and validate successful database description exchange rather than masking the check. This treats the fault shown by Ridgefield Carrier: OSPF database description negotiation can reject incompatible interface MTUs even after hello packets establish initial communication. Confirm success when the two peers progress through database synchronization to Full and agree on reachable link-state information.

Incorrect Answers

B:

The proposal changes IS-IS adjacency circuit level; that is not the failure isolated by the facts. It could leave OSPF MTU negotiation unresolved even if its own test passed. OSPF database description negotiation can reject incompatible interface MTUs even after hello packets establish initial communication.

C:

Apply a scoped OSPF export policy to originate only the approved active source prefix and confirm the receiving routers learn it. That could help in a case involving OSPF external route export. This failure instead depends on OSPF MTU negotiation; OSPF database description negotiation can reject incompatible interface MTUs even after hello packets establish initial communication.

D:

The proposal changes OSPF designated router election; that is not the failure isolated by the facts. It could leave OSPF MTU negotiation unresolved even if its own test passed. OSPF database description negotiation can reject incompatible interface MTUs even after hello packets establish initial communication.

Question 399

The operations group at fictional Riverbend Exchange, working on a redundant core router pair, finds: After a new access layer is attached, the planned root bridge loses root position because an untrusted designated-port neighbor has better bridge priority. Which observation would most directly establish that the reported failure has been repaired?

  1. The alternate port assumes an appropriate forwarding role on failure without allowing simultaneous Layer 2 loops.
  2. The approved root remains root despite inferior-site superior-BPDU injection, and the boundary behaves as designed.
  3. The aggregate is active only with the expected contributors and disappears when the contributor precondition is removed.
  4. Adjacent devices report matching MST region configuration and VLANs map to the same intended instances.

Explanation

Correct Answer

B:

The approved root remains root despite inferior-site superior-BPDU injection, and the boundary behaves as designed. It tests the failed behavior itself rather than merely confirming that a configuration was committed. Root protection blocks acceptance of an unexpected superior root across designated boundary ports; it is not the same as BPDU edge protection. Applied here, the relevant facts are: After a new access layer is attached, the planned root bridge loses root position because an untrusted designated-port neighbor has better bridge priority. The question asks which observation would most directly establish that the reported failure has been repaired.

Incorrect Answers

A:

This measurement tests RSTP alternate port reconvergence; it cannot distinguish success from failure for the observed RSTP root protection condition. Root protection blocks acceptance of an unexpected superior root across designated boundary ports; it is not the same as BPDU edge protection. Applied here, the relevant facts are: After a new access layer is attached, the planned root bridge loses root position because an untrusted designated-port neighbor has better bridge priority. The question asks which observation would most directly establish that the reported failure has been repaired.

C:

This measurement tests aggregate route contributor; it cannot distinguish success from failure for the observed RSTP root protection condition. Root protection blocks acceptance of an unexpected superior root across designated boundary ports; it is not the same as BPDU edge protection.

D:

Adjacent devices report matching MST region configuration and VLANs map to the same intended instances. It would validate a separate MSTP region consistency operation, not the change needed here. Confirm instead that the approved root remains root despite inferior-site superior-BPDU injection, and the boundary behaves as designed.

Question 400

At fictional Juniper Glen Telecom, during a dual-stack transit pilot, engineers report: Two routers form an IS-IS adjacency but IPv6 destinations are missing because the required address-family reachability information is not advertised. Which networking principle most accurately explains the observed failure?

  1. IS-IS uses Level 1 within an area and Level 2 between areas; an L1 router needs an appropriate inter-area exit or route leak.
  2. OSPF chooses lowest-cost paths computed from link-state topology; a Full adjacency alone does not guarantee the desired route preference.
  3. The IS-IS NET encodes area membership and system identity, which must be consistent with the planned level and unique per node.
  4. IS-IS uses TLVs inside its PDUs to encode prefix and protocol capabilities; adjacency alone is not proof of expected reachability advertisements.

Explanation

Correct Answer

D:

IS-IS uses TLVs inside its PDUs to encode prefix and protocol capabilities; adjacency alone is not proof of expected reachability advertisements. That is the specific distinction behind the observed outage. The targeted fix is to inspect the supported and advertised IS-IS reachability TLVs and configure the correct address family on the relevant links. Applied here, the relevant facts are: Two routers form an IS-IS adjacency but IPv6 destinations are missing because the required address-family reachability information is not advertised. The question asks which networking principle most accurately explains the observed failure.

Incorrect Answers

A:

This principle matters when troubleshooting IS-IS L1 and L2 reachability, but using it here mistakes a different failure mode for IS-IS TLV reachability. The relevant distinction is: IS-IS uses TLVs inside its PDUs to encode prefix and protocol capabilities; adjacency alone is not proof of expected reachability advertisements. Applied here, the relevant facts are: Two routers form an IS-IS adjacency but IPv6 destinations are missing because the required address-family reachability information is not advertised. The question asks which networking principle most accurately explains the observed failure.

B:

This principle matters when troubleshooting OSPF interface metric selection, but using it here mistakes a different failure mode for IS-IS TLV reachability. The relevant distinction is: IS-IS uses TLVs inside its PDUs to encode prefix and protocol capabilities; adjacency alone is not proof of expected reachability advertisements.

C:

The IS-IS NET encodes area membership and system identity, which must be consistent with the planned level and unique per node. Those conditions do not account for the specific IS-IS TLV reachability problem reported by Juniper Glen Telecom.

Service Provider Routing and Switching, Specialist (JNCIS-SP) (JN0-364) Practice Tests