Cisco 350-501 Practice Test 19
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.
Question 181
A service provider network engineer is reviewing this backbone or customer-service scenario: A router's static high interface cost forces a long recovery path after link restoration, but operations assumes shortest physical distance chooses the OSPF route. 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.
- Let customer-facing interface speed labels replace OSPF metrics without checking the routers' actual cost calculation.
- Tune consistent OSPF cost or reference-bandwidth settings and validate reconvergence under controlled link failures.
- Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation.
- Assign unique IS-IS system IDs and consistent area identifiers for Level-1 adjacency, with proper Level-2 reachability across areas.
Explanation
Correct Answer
B:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A router's static high interface cost forces a long recovery path after link restoration, but operations assumes shortest physical distance chooses the OSPF route.
Incorrect Answers
A:OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance. Applied case: A router's static high interface cost forces a long recovery path after link restoration, but operations assumes shortest physical distance chooses the OSPF route.
C:Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation. A router's static high interface cost forces a long recovery path after link restoration, but operations assumes shortest physical distance chooses the OSPF route.
D:Assign unique IS-IS system IDs and consistent area identifiers for Level-1 adjacency, with proper Level-2 reachability across areas. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
Question 182
A Cisco service provider design review finds: A router's static high interface cost forces a long recovery path after link restoration, but operations assumes shortest physical distance chooses the OSPF route. 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.
- 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 SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
- Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
- IS-IS NET encodes an area and unique system identifier; Level-1 flooding is area scoped while Level-2 connects interarea backbone reachability.
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 router's static high interface cost forces a long recovery path after link restoration, but operations assumes shortest physical distance chooses the OSPF route.
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 SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
C:Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
D:IS-IS NET encodes an area and unique system identifier; Level-1 flooding is area scoped while Level-2 connects interarea backbone reachability. A router's static high interface cost forces a long recovery path after link restoration, but operations assumes shortest physical distance chooses the OSPF route.
Question 183
The service provider operations team has not yet approved a change. Current evidence indicates: A router's static high interface cost forces a long recovery path after link restoration, but operations assumes shortest physical distance chooses the OSPF route. 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.
- Inspect negotiated additional-path capability, backup path RIB and FIB entries and forwarding interruption during simulated failure.
- Check neighbor state transitions, interface MTU, hello and dead intervals, area type and network type on both peers.
- Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests.
Explanation
Correct Answer
D:OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance. This check tests the actual routing, transport or service boundary before an operationally risky response.
Incorrect Answers
A:Inspect IPv6 link-local neighbors, interface instance and area data, OSPFv3 LSDB and installed IPv6 routes. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
B:Inspect negotiated additional-path capability, backup path RIB and FIB entries and forwarding interruption during simulated failure. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
C:Check neighbor state transitions, interface MTU, hello and dead intervals, area type and network type on both peers. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
Question 184
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A router's static high interface cost forces a long recovery path after link restoration, but operations assumes shortest physical distance chooses the OSPF route. 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.
- The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure.
- Selected paths follow intended costs and the backup route takes over safely after a neighbor or link failure.
- The intended Level-1 or Level-2 adjacency forms and the routers exchange consistent link-state information without dropping required hello traffic.
- Genuine path loss is detected promptly while minor delay variation does not trigger avoidable adjacency resets.
Explanation
Correct Answer
B:OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance. The approved implementation step was: Tune consistent OSPF cost or reference-bandwidth settings and validate reconvergence under controlled link failures.
Incorrect Answers
A:The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
C:The intended Level-1 or Level-2 adjacency forms and the routers exchange consistent link-state information without dropping required hello traffic. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
D:Genuine path loss is detected promptly while minor delay variation does not trigger avoidable adjacency resets. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
Question 185
An implementation sign-off request identifies the following problem: A router's static high interface cost forces a long recovery path after link restoration, but operations assumes shortest physical distance chooses the OSPF route. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- Change: Tune consistent OSPF cost or reference-bandwidth settings and validate reconvergence under controlled link failures. Verify: Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests.
- Change: Apply supported consistent metric style and tune link costs to the provider's intended shortest-path and capacity policy. Verify: Review link metric TLVs, enabled metric style, SPF database and before-after path selection for two candidate routes.
- 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.
- Change: Coordinate BFD with supported routing clients and realistic detect-multiplier and interval settings for stable rapid failure detection. Verify: Compare BFD session state, negotiated intervals, packet drops and routing convergence after controlled loss and benign congestion tests.
Explanation
Correct Answer
A:OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance. The change is successful only when: Selected paths follow intended costs and the backup route takes over safely after a neighbor or link failure.
Incorrect Answers
B:Change: Apply supported consistent metric style and tune link costs to the provider's intended shortest-path and capacity policy. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
C:Change: Select single- or multi-topology IS-IS according to dual-stack forwarding requirements and verify both address-family reachability and advertised topology data. OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
D:Change: Coordinate BFD with supported routing clients and realistic detect-multiplier and interval settings for stable rapid failure detection.
Question 186
A service provider network engineer is reviewing this backbone or customer-service scenario: A provider establishes an external BGP session with the wrong remote autonomous-system number and sees repeated OPEN errors. A proposed shortcut is: Force two unrelated routers to use arbitrary AS values and expect transport connectivity alone to bypass BGP OPEN validation. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Force two unrelated routers to use arbitrary AS values and expect transport connectivity alone to bypass BGP OPEN validation.
- Align peer AS, transport source, addressing, family activation and supported eBGP hop reachability for the actual topology.
- Assign unique IS-IS system IDs and consistent area identifiers for Level-1 adjacency, with proper Level-2 reachability across areas.
- Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements.
Explanation
Correct Answer
B:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A provider establishes an external BGP session with the wrong remote autonomous-system number and sees repeated OPEN errors.
Incorrect Answers
A:BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
C:Assign unique IS-IS system IDs and consistent area identifiers for Level-1 adjacency, with proper Level-2 reachability across areas. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
D:Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
Question 187
A Cisco service provider design review finds: A provider establishes an external BGP session with the wrong remote autonomous-system number and sees repeated OPEN errors. The team proposes: Align peer AS, transport source, addressing, family activation and supported eBGP hop reachability for the actual topology. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
- BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
- BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
- BFD detects data-path forwarding failure independently of slower routing hellos but extreme timer settings can create false failures.
Explanation
Correct Answer
C:Demonstrable success requires: Intended EBGP adjacencies establish securely and exchange only approved prefixes in the selected address family. Applied case: A provider establishes an external BGP session with the wrong remote autonomous-system number and sees repeated OPEN errors.
Incorrect Answers
A:This option addresses a different service provider engineering topic (BGP route-policy communities and provider preference) rather than the documented eBGP IPv4 IPv6 peer and multihop session design decision.
B:BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
D:BFD detects data-path forwarding failure independently of slower routing hellos but extreme timer settings can create false failures. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
Question 188
The service provider operations team has not yet approved a change. Current evidence indicates: A provider establishes an external BGP session with the wrong remote autonomous-system number and sees repeated OPEN errors. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Inspect BGP neighbor transport state, local and remote AS, update source, TCP reachability and IPv4 or IPv6 address-family activation.
- Check route-reflector client relationships, originator and cluster attributes, BGP next-hop resolution and the RIB versus FIB.
- Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests.
- Compare BFD session state, negotiated intervals, packet drops and routing convergence after controlled loss and benign congestion tests.
Explanation
Correct Answer
A:BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions. Applied case: A provider establishes an external BGP session with the wrong remote autonomous-system number and sees repeated OPEN errors.
Incorrect Answers
B:Check route-reflector client relationships, originator and cluster attributes, BGP next-hop resolution and the RIB versus FIB. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
C:Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests. A provider establishes an external BGP session with the wrong remote autonomous-system number and sees repeated OPEN errors.
D:Compare BFD session state, negotiated intervals, packet drops and routing convergence after controlled loss and benign congestion tests. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
Question 189
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A provider establishes an external BGP session with the wrong remote autonomous-system number and sees repeated OPEN errors. 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.
- Intended EBGP adjacencies establish securely and exchange only approved prefixes in the selected address family.
- Stable OSPFv3 adjacencies advertise the intended IPv6 prefixes with reachable next hops.
- Accepted members forward correctly, aggregate capacity reflects active links and service survives an individual member failure.
- The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure.
Explanation
Correct Answer
A:BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions. The result must be validated using the documented device, service or access context.
Incorrect Answers
B:Stable OSPFv3 adjacencies advertise the intended IPv6 prefixes with reachable next hops. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
C:Accepted members forward correctly, aggregate capacity reflects active links and service survives an individual member failure. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
D:The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
Question 190
For an original SPCOR service-provider engineering scenario, consider: A provider establishes an external BGP session with the wrong remote autonomous-system number and sees repeated OPEN errors. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Change: Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary.
- Check: Inspect BGP neighbor transport state, local and remote AS, update source, TCP reachability and IPv4 or IPv6 address-family activation.
- Check: Evaluate a test table with allowed, denied and boundary prefixes against actual show-policy and BGP advertised-routes evidence.
- Force two unrelated routers to use arbitrary AS values and expect transport connectivity alone to bypass BGP OPEN validation.
- Change: Align peer AS, transport source, addressing, family activation and supported eBGP hop reachability for the actual topology.
Explanation
Correct Answer
B:BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions. Acceptance: Intended EBGP adjacencies establish securely and exchange only approved prefixes in the selected address family.
E:BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions. Evidence: Inspect BGP neighbor transport state, local and remote AS, update source, TCP reachability and IPv4 or IPv6 address-family activation.
Incorrect Answers
A:Change: Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
C:Check: Evaluate a test table with allowed, denied and boundary prefixes against actual show-policy and BGP advertised-routes evidence. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
D:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
