Cisco 350-501 Practice Test 16
Question 150
For an original SPCOR service-provider engineering scenario, consider: Two OSPFv2 core routers have matching hello and dead timers but stay in ExStart because their interface MTU assumptions differ. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Change: Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements.
- Check: Check neighbor state transitions, interface MTU, hello and dead intervals, area type and network type on both peers.
- Check: Compare area LSDB LSA types, ABR summaries, default injection and actual endpoint reachability for inside and outside addresses.
- Set every OSPF interface to a random area and disable all checks instead of identifying the actual failed adjacency stage.
- Change: Verify OSPFv3 interface activation, matching area and instance settings and IPv6 address-family route advertisement before expecting end-to-end forwarding.
Explanation
Correct Answer
A:OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior. Acceptance: Expected neighbors reach the appropriate full adjacency state and exchange synchronized LSDB information without hidden MTU mismatches.
B:OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior. Required intervention: Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements.
Incorrect Answers
C:Check: Compare area LSDB LSA types, ABR summaries, default injection and actual endpoint reachability for inside and outside addresses. OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
D:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
E:Change: Verify OSPFv3 interface activation, matching area and instance settings and IPv6 address-family route advertisement before expecting end-to-end forwarding. OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
Question 151
A service provider network engineer is reviewing this backbone or customer-service scenario: An access-facing OSPF link never advances past 2-Way in a network type requiring a full adjacency, while the engineer ignores DR/BDR expectations. A proposed shortcut is: Set every OSPF interface to a random area and disable all checks instead of identifying the actual failed adjacency stage. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Use the platform's supported policy language, explicit prefix sets and match sequencing to permit only intended routes and apply actions at the correct direction.
- Set every OSPF interface to a random area and disable all checks instead of identifying the actual failed adjacency stage.
- Coordinate BFD with supported routing clients and realistic detect-multiplier and interval settings for stable rapid failure detection.
- Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements.
Explanation
Correct Answer
D:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: An access-facing OSPF link never advances past 2-Way in a network type requiring a full adjacency, while the engineer ignores DR/BDR expectations.
Incorrect Answers
A:Use the platform's supported policy language, explicit prefix sets and match sequencing to permit only intended routes and apply actions at the correct direction. OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
B:OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior. Applied case: An access-facing OSPF link never advances past 2-Way in a network type requiring a full adjacency, while the engineer ignores DR/BDR expectations.
C:Coordinate BFD with supported routing clients and realistic detect-multiplier and interval settings for stable rapid failure detection. An access-facing OSPF link never advances past 2-Way in a network type requiring a full adjacency, while the engineer ignores DR/BDR expectations.
Question 152
A Cisco service provider design review finds: An access-facing OSPF link never advances past 2-Way in a network type requiring a full adjacency, while the engineer ignores DR/BDR expectations. The team proposes: Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- LACP negotiates compatible members into a logical bundle while per-flow hashing commonly keeps a flow on one member to preserve packet order.
- OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
- OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
- BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
Explanation
Correct Answer
B:Demonstrable success requires: Expected neighbors reach the appropriate full adjacency state and exchange synchronized LSDB information without hidden MTU mismatches. Applied case: An access-facing OSPF link never advances past 2-Way in a network type requiring a full adjacency, while the engineer ignores DR/BDR expectations.
Incorrect Answers
A:LACP negotiates compatible members into a logical bundle while per-flow hashing commonly keeps a flow on one member to preserve packet order. OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
C:OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area. OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
D:This option addresses a different service provider engineering topic (eBGP IPv4 IPv6 peer and multihop session design) rather than the documented OSPFv2 neighbor state and MTU mismatch decision.
Question 153
The service provider operations team has not yet approved a change. Current evidence indicates: An access-facing OSPF link never advances past 2-Way in a network type requiring a full adjacency, while the engineer ignores DR/BDR expectations. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests.
- Compare valid path candidates and detailed BGP attributes under a test prefix, then trace which decision criterion breaks the tie.
- Measure neighbor resets, stale route retention, forwarding counters and route processing after a planned RP switchover.
- Check neighbor state transitions, interface MTU, hello and dead intervals, area type and network type on both peers.
Explanation
Correct Answer
D:OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior. Confirm afterward that: Expected neighbors reach the appropriate full adjacency state and exchange synchronized LSDB information without hidden MTU mismatches.
Incorrect Answers
A:This option addresses a different service provider engineering topic (OSPF route cost and convergence after link changes) rather than the documented OSPFv2 neighbor state and MTU mismatch decision.
B:Compare valid path candidates and detailed BGP attributes under a test prefix, then trace which decision criterion breaks the tie. OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
C:Measure neighbor resets, stale route retention, forwarding counters and route processing after a planned RP switchover. OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
Question 154
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: An access-facing OSPF link never advances past 2-Way in a network type requiring a full adjacency, while the engineer ignores DR/BDR expectations. The carrier operations owner needs positive and negative tests showing existing customer services remain available. Which acceptance result demonstrates correct service provider forwarding and control behavior without disrupting authorized workflows? Select ONE best answer.
- Only planned prefixes cross the protocol boundary once and core convergence remains stable under service-route churn.
- The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure.
- Expected neighbors reach the appropriate full adjacency state and exchange synchronized LSDB information without hidden MTU mismatches.
- Valid alternate paths are visible and traffic shifts within expected service objectives when the primary next hop fails.
Explanation
Correct Answer
C:OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior. The approved implementation step was: Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements.
Incorrect Answers
A:Only planned prefixes cross the protocol boundary once and core convergence remains stable under service-route churn. An access-facing OSPF link never advances past 2-Way in a network type requiring a full adjacency, while the engineer ignores DR/BDR expectations.
B:The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure. OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
D:Valid alternate paths are visible and traffic shifts within expected service objectives when the primary next hop fails. OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
Question 155
An implementation sign-off request identifies the following problem: An access-facing OSPF link never advances past 2-Way in a network type requiring a full adjacency, while the engineer ignores DR/BDR expectations. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- Change: Restrict redistribution using explicit route policy and tags, and maintain a scalable separation of service prefixes from core IGP reachability. Verify: Trace sample source routes, redistribution policy hits, tags, LSDB or LSP size and resulting RIB changes across both boundaries.
- Change: Enable compatible path diversity or BGP PIC mechanisms where supported and verify backup data-plane programming before a failure. Verify: Inspect negotiated additional-path capability, backup path RIB and FIB entries and forwarding interruption during simulated failure.
- Change: Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements. Verify: Check neighbor state transitions, interface MTU, hello and dead intervals, area type and network type on both peers.
- Change: Select single- or multi-topology IS-IS according to dual-stack forwarding requirements and verify both address-family reachability and advertised topology data. Verify: Compare IS-IS IPv4 and IPv6 LSP TLVs, topology IDs, next-hop tables and controlled ping tests for each family.
Explanation
Correct Answer
C:OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior. The change is successful only when: Expected neighbors reach the appropriate full adjacency state and exchange synchronized LSDB information without hidden MTU mismatches.
Incorrect Answers
A:Change: Restrict redistribution using explicit route policy and tags, and maintain a scalable separation of service prefixes from core IGP reachability. OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
B:Change: Enable compatible path diversity or BGP PIC mechanisms where supported and verify backup data-plane programming before a failure.
D:Change: Select single- or multi-topology IS-IS according to dual-stack forwarding requirements and verify both address-family reachability and advertised topology data.
Question 156
A service provider network engineer is reviewing this backbone or customer-service scenario: A carrier uses OSPFv3 for IPv6 core connectivity but enables the process without activating the intended interfaces and sees no IPv6 prefixes. A proposed shortcut is: Assume OSPFv2 neighbor establishment alone causes the same interfaces to participate in OSPFv3 automatically. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Assume OSPFv2 neighbor establishment alone causes the same interfaces to participate in OSPFv3 automatically.
- Assign unique IS-IS system IDs and consistent area identifiers for Level-1 adjacency, with proper Level-2 reachability across areas.
- Verify OSPFv3 interface activation, matching area and instance settings and IPv6 address-family route advertisement before expecting end-to-end forwarding.
- Choose the appropriate IPv6 transition and address-sharing model for subscriber connectivity, and test mapping state and application behavior end to end.
Explanation
Correct Answer
C:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A carrier uses OSPFv3 for IPv6 core connectivity but enables the process without activating the intended interfaces and sees no IPv6 prefixes.
Incorrect Answers
A:OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
B:Assign unique IS-IS system IDs and consistent area identifiers for Level-1 adjacency, with proper Level-2 reachability across areas. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
D:Choose the appropriate IPv6 transition and address-sharing model for subscriber connectivity, and test mapping state and application behavior end to end. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
Question 157
A Cisco service provider design review finds: A carrier uses OSPFv3 for IPv6 core connectivity but enables the process without activating the intended interfaces and sees no IPv6 prefixes. The team proposes: Verify OSPFv3 interface activation, matching area and instance settings and IPv6 address-family route advertisement before expecting end-to-end forwarding. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- NAT64 translates between IPv6 and IPv4 with suitable discovery, while DS-Lite tunnels subscriber IPv4 over IPv6 to a shared CGN function; MAP-T uses different translation rules.
- OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
- Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
- BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
Explanation
Correct Answer
B:Relevant validation before approval: Inspect IPv6 link-local neighbors, interface instance and area data, OSPFv3 LSDB and installed IPv6 routes.
Incorrect Answers
A:NAT64 translates between IPv6 and IPv4 with suitable discovery, while DS-Lite tunnels subscriber IPv4 over IPv6 to a shared CGN function; MAP-T uses different translation rules. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
C:Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
D:This option addresses a different service provider engineering topic (BGP path selection weight local preference and AS path) rather than the documented OSPFv3 IPv6 addressing and adjacencies decision.
Question 158
The service provider operations team has not yet approved a change. Current evidence indicates: A carrier uses OSPFv3 for IPv6 core connectivity but enables the process without activating the intended interfaces and sees no IPv6 prefixes. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Inspect IPv6 link-local neighbors, interface instance and area data, OSPFv3 LSDB and installed IPv6 routes.
- Trace sample source routes, redistribution policy hits, tags, LSDB or LSP size and resulting RIB changes across both boundaries.
- Inspect IS-IS neighbor state, hello capture, interface MTU and level configuration at both endpoints.
- Examine NET values, level adjacency state, LSP originator IDs and intended area boundaries on a two-area diagram.
Explanation
Correct Answer
A:OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area. Applied case: A carrier uses OSPFv3 for IPv6 core connectivity but enables the process without activating the intended interfaces and sees no IPv6 prefixes.
Incorrect Answers
B:Trace sample source routes, redistribution policy hits, tags, LSDB or LSP size and resulting RIB changes across both boundaries. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
C:Inspect IS-IS neighbor state, hello capture, interface MTU and level configuration at both endpoints. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
D:Examine NET values, level adjacency state, LSP originator IDs and intended area boundaries on a two-area diagram. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
Question 159
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A carrier uses OSPFv3 for IPv6 core connectivity but enables the process without activating the intended interfaces and sees no IPv6 prefixes. The carrier operations owner needs positive and negative tests showing existing customer services remain available. Which acceptance result demonstrates correct service provider forwarding and control behavior without disrupting authorized workflows? Select ONE best answer.
- Unique node identities produce the intended L1 or L2 adjacencies and routes cross only supported level boundaries.
- Genuine path loss is detected promptly while minor delay variation does not trigger avoidable adjacency resets.
- Stub or normal areas receive only intended advertisements and no unreachable discontiguous summary is treated as valid service connectivity.
- Stable OSPFv3 adjacencies advertise the intended IPv6 prefixes with reachable next hops.
Explanation
Correct Answer
D:OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area. The result must be validated using the documented device, service or access context.
Incorrect Answers
A:Unique node identities produce the intended L1 or L2 adjacencies and routes cross only supported level boundaries. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
B:Genuine path loss is detected promptly while minor delay variation does not trigger avoidable adjacency resets. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
C:Stub or normal areas receive only intended advertisements and no unreachable discontiguous summary is treated as valid service connectivity. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
Question 160
For an original SPCOR service-provider engineering scenario, consider: A carrier uses OSPFv3 for IPv6 core connectivity but enables the process without activating the intended interfaces and sees no IPv6 prefixes. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Change: Verify OSPFv3 interface activation, matching area and instance settings and IPv6 address-family route advertisement before expecting end-to-end forwarding.
- Check: Inspect IPv6 link-local neighbors, interface instance and area data, OSPFv3 LSDB and installed IPv6 routes.
- Assume OSPFv2 neighbor establishment alone causes the same interfaces to participate in OSPFv3 automatically.
- Change: Deploy route reflection with deliberate client and cluster design and preserve IGP reachability to advertised BGP next hops.
- Check: Examine advertised route attributes per peer, remote looking-glass paths and measured ingress flows before and after the change.
Explanation
Correct Answer
A:OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area. Evidence: Inspect IPv6 link-local neighbors, interface instance and area data, OSPFv3 LSDB and installed IPv6 routes.
B:OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area. Inspect IPv6 link-local neighbors, interface instance and area data, OSPFv3 LSDB and installed IPv6 routes.
Incorrect Answers
C:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
D:This option addresses a different service provider engineering topic (iBGP route reflector cluster and next-hop reachability) rather than the documented OSPFv3 IPv6 addressing and adjacencies decision.
E:Check: Examine advertised route attributes per peer, remote looking-glass paths and measured ingress flows before and after the change. OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
