Cisco 350-501 Practice Test 18
Question 170
For an original SPCOR service-provider engineering scenario, consider: A provider configures a stub area but expects external LSAs to be flooded into it unchanged, then investigates missing type-5 routes. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Change: Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation.
- Advertise a blanket aggregate for unrelated prefixes and expect all OSPF external LSAs to enter every stub area.
- Check: Compare area LSDB LSA types, ABR summaries, default injection and actual endpoint reachability for inside and outside addresses.
- Change: Match IS-IS level operation and interface parameters before expecting LSP exchange and route installation across a service provider core link.
- Check: Examine NET values, level adjacency state, LSP originator IDs and intended area boundaries on a two-area diagram.
Explanation
Correct Answer
A:OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly. Acceptance: Stub or normal areas receive only intended advertisements and no unreachable discontiguous summary is treated as valid service connectivity.
C:OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly. Required intervention: Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation.
Incorrect Answers
B:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
D:Change: Match IS-IS level operation and interface parameters before expecting LSP exchange and route installation across a service provider core link. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
E:Check: Examine NET values, level adjacency state, LSP originator IDs and intended area boundaries on a two-area diagram. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
Question 171
A service provider network engineer is reviewing this backbone or customer-service scenario: Two area border routers summarize a discontiguous address block and accidentally advertise reachability to unused prefixes toward the core. A proposed shortcut is: Advertise a blanket aggregate for unrelated prefixes and expect all OSPF external LSAs to enter every stub area. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Align peer AS, transport source, addressing, family activation and supported eBGP hop reachability for the actual topology.
- Choose the appropriate IPv6 transition and address-sharing model for subscriber connectivity, and test mapping state and application behavior end to end.
- Advertise a blanket aggregate for unrelated prefixes and expect all OSPF external LSAs to enter every stub area.
- Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation.
Explanation
Correct Answer
D:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
Incorrect Answers
A:Align peer AS, transport source, addressing, family activation and supported eBGP hop reachability for the actual topology. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
B:Choose the appropriate IPv6 transition and address-sharing model for subscriber connectivity, and test mapping state and application behavior end to end. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
C:OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly. Use this instead: Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation.
Question 172
A Cisco service provider design review finds: Two area border routers summarize a discontiguous address block and accidentally advertise reachability to unused prefixes toward the core. The team proposes: Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation. 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.
- Add-Paths can advertise multiple BGP paths under negotiated capability while PIC accelerates convergence using preinstalled repair or next-hop structures.
- OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
- Redistribution changes protocol scope and metrics; uncontrolled mutual redistribution can create loops and excessive IGP state.
Explanation
Correct Answer
C:Demonstrable success requires: Stub or normal areas receive only intended advertisements and no unreachable discontiguous summary is treated as valid service connectivity. This principle explains the proposed technical approach, which is: Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation.
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. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
B:Add-Paths can advertise multiple BGP paths under negotiated capability while PIC accelerates convergence using preinstalled repair or next-hop structures. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
D:Redistribution changes protocol scope and metrics; uncontrolled mutual redistribution can create loops and excessive IGP state. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
Question 173
The service provider operations team has not yet approved a change. Current evidence indicates: Two area border routers summarize a discontiguous address block and accidentally advertise reachability to unused prefixes toward the core. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Compare area LSDB LSA types, ABR summaries, default injection and actual endpoint reachability for inside and outside addresses.
- Inspect IPv6 link-local neighbors, interface instance and area data, OSPFv3 LSDB and installed IPv6 routes.
- Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests.
- Examine NET values, level adjacency state, LSP originator IDs and intended area boundaries on a two-area diagram.
Explanation
Correct Answer
A:OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly. Confirm afterward that: Stub or normal areas receive only intended advertisements and no unreachable discontiguous summary is treated as valid service connectivity.
Incorrect Answers
B:Inspect IPv6 link-local neighbors, interface instance and area data, OSPFv3 LSDB and installed IPv6 routes. Two area border routers summarize a discontiguous address block and accidentally advertise reachability to unused prefixes toward the core.
C:Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests. Two area border routers summarize a discontiguous address block and accidentally advertise reachability to unused prefixes toward the core.
D:Examine NET values, level adjacency state, LSP originator IDs and intended area boundaries on a two-area diagram. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
Question 174
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: Two area border routers summarize a discontiguous address block and accidentally advertise reachability to unused prefixes toward the core. 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.
- Stub or normal areas receive only intended advertisements and no unreachable discontiguous summary is treated as valid service connectivity.
- Genuine path loss is detected promptly while minor delay variation does not trigger avoidable adjacency resets.
- Expected neighbors reach the appropriate full adjacency state and exchange synchronized LSDB information without hidden MTU mismatches.
- Only planned prefixes cross the protocol boundary once and core convergence remains stable under service-route churn.
Explanation
Correct Answer
A:OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly. Applied case: Two area border routers summarize a discontiguous address block and accidentally advertise reachability to unused prefixes toward the core.
Incorrect Answers
B:Genuine path loss is detected promptly while minor delay variation does not trigger avoidable adjacency resets. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
C:Expected neighbors reach the appropriate full adjacency state and exchange synchronized LSDB information without hidden MTU mismatches. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
D:Only planned prefixes cross the protocol boundary once and core convergence remains stable under service-route churn. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
Question 175
An implementation sign-off request identifies the following problem: Two area border routers summarize a discontiguous address block and accidentally advertise reachability to unused prefixes toward the core. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- Change: Match IS-IS level operation and interface parameters before expecting LSP exchange and route installation across a service provider core link. Verify: Inspect IS-IS neighbor state, hello capture, interface MTU and level configuration at both endpoints.
- Change: Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation. Verify: Compare area LSDB LSA types, ABR summaries, default injection and actual endpoint reachability for inside and outside addresses.
- 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: Diagnose the affected protocol's actual session prerequisites and advertisement scope before changing unrelated routing controls. Verify: Compare per-protocol neighbor state, error messages, encapsulation, path reachability, authentication and interface counters.
Explanation
Correct Answer
B:OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly. The change is successful only when: Stub or normal areas receive only intended advertisements and no unreachable discontiguous summary is treated as valid service connectivity.
Incorrect Answers
A:Change: Match IS-IS level operation and interface parameters before expecting LSP exchange and route installation across a service provider core link. Two area border routers summarize a discontiguous address block and accidentally advertise reachability to unused prefixes toward the core.
C:Change: Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements. OSPF area types control which LSA classes are accepted while ABRs can summarize routes; a summary may hide unavailable more-specifics if chosen carelessly.
D:Change: Diagnose the affected protocol's actual session prerequisites and advertisement scope before changing unrelated routing controls. Two area border routers summarize a discontiguous address block and accidentally advertise reachability to unused prefixes toward the core.
Question 176
A service provider network engineer is reviewing this backbone or customer-service scenario: A service provider raises interface bandwidth yet the configured reference bandwidth causes both the old and upgraded link to appear with the same OSPF cost. A proposed shortcut is: Let customer-facing interface speed labels replace OSPF metrics without checking the routers' actual cost calculation. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Diagnose the affected protocol's actual session prerequisites and advertisement scope before changing unrelated routing controls.
- Tune consistent OSPF cost or reference-bandwidth settings and validate reconvergence under controlled link failures.
- Let customer-facing interface speed labels replace OSPF metrics without checking the routers' actual cost calculation.
- Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation.
Explanation
Correct Answer
B:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A service provider raises interface bandwidth yet the configured reference bandwidth causes both the old and upgraded link to appear with the same OSPF cost.
Incorrect Answers
A:Diagnose the affected protocol's actual session prerequisites and advertisement scope before changing unrelated routing controls. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
C:OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
D:Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
Question 177
A Cisco service provider design review finds: A service provider raises interface bandwidth yet the configured reference bandwidth causes both the old and upgraded link to appear with the same OSPF cost. The team proposes: Tune consistent OSPF cost or reference-bandwidth settings and validate reconvergence under controlled link failures. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- IS-IS NET encodes an area and unique system identifier; Level-1 flooding is area scoped while Level-2 connects interarea backbone reachability.
- OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
- Route filtering is an ordered policy decision with platform-specific syntax and implicit outcomes; bad matching or direction can leak or drop routes.
- OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area.
Explanation
Correct Answer
B:Relevant validation before approval: Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests. Applied case: A service provider raises interface bandwidth yet the configured reference bandwidth causes both the old and upgraded link to appear with the same OSPF cost.
Incorrect Answers
A:IS-IS NET encodes an area and unique system identifier; Level-1 flooding is area scoped while Level-2 connects interarea backbone reachability. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
C:Route filtering is an ordered policy decision with platform-specific syntax and implicit outcomes; bad matching or direction can leak or drop routes. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
D:OSPFv3 neighbors commonly use IPv6 link-local transport while routing advertisements and instances depend on the enabled topology and area. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
Question 178
The service provider operations team has not yet approved a change. Current evidence indicates: A service provider raises interface bandwidth yet the configured reference bandwidth causes both the old and upgraded link to appear with the same OSPF cost. 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.
- Trace sample source routes, redistribution policy hits, tags, LSDB or LSP size and resulting RIB changes across both boundaries.
- Trace a known client flow through DNS resolution, IPv4 or IPv6 encapsulation, translator bindings and return path with packet captures.
- Examine NET values, level adjacency state, LSP originator IDs and intended area boundaries on a two-area diagram.
Explanation
Correct Answer
A:OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance. Applied case: A service provider raises interface bandwidth yet the configured reference bandwidth causes both the old and upgraded link to appear with the same OSPF cost.
Incorrect Answers
B:Trace sample source routes, redistribution policy hits, tags, LSDB or LSP size and resulting RIB changes across both boundaries. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
C:Trace a known client flow through DNS resolution, IPv4 or IPv6 encapsulation, translator bindings and return path with packet captures. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
D:Examine NET values, level adjacency state, LSP originator IDs and intended area boundaries on a two-area diagram. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
Question 179
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A service provider raises interface bandwidth yet the configured reference bandwidth causes both the old and upgraded link to appear with the same OSPF cost. 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.
- Selected paths follow intended costs and the backup route takes over safely after a neighbor or link failure.
- Stub or normal areas receive only intended advertisements and no unreachable discontiguous summary is treated as valid service connectivity.
- Only planned prefixes cross the protocol boundary once and core convergence remains stable under service-route churn.
- Authorized IPv6 and shared-IPv4 applications work with correct port mappings, accountability and predictable failure handling.
Explanation
Correct Answer
A:OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance. The result must be validated using the documented device, service or access context.
Incorrect Answers
B:Stub or normal areas receive only intended advertisements and no unreachable discontiguous summary is treated as valid service connectivity. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
C:Only planned prefixes cross the protocol boundary once and core convergence remains stable under service-route churn. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
D:Authorized IPv6 and shared-IPv4 applications work with correct port mappings, accountability and predictable failure handling. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
Question 180
For an original SPCOR service-provider engineering scenario, consider: A service provider raises interface bandwidth yet the configured reference bandwidth causes both the old and upgraded link to appear with the same OSPF cost. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Change: Enable compatible path diversity or BGP PIC mechanisms where supported and verify backup data-plane programming before a failure.
- Check: Evaluate a test table with allowed, denied and boundary prefixes against actual show-policy and BGP advertised-routes evidence.
- Let customer-facing interface speed labels replace OSPF metrics without checking the routers' actual cost calculation.
- Check: Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests.
- Change: Tune consistent OSPF cost or reference-bandwidth settings and validate reconvergence under controlled link failures.
Explanation
Correct Answer
D:OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance. Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests.
E:OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance. Evidence: Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests.
Incorrect Answers
A:Change: Enable compatible path diversity or BGP PIC mechanisms where supported and verify backup data-plane programming before a failure. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
B:Check: Evaluate a test table with allowed, denied and boundary prefixes against actual show-policy and BGP advertised-routes evidence. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
C:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
