Cisco 350-501 Practice Test 29
Question 280
For an original SPCOR service-provider engineering scenario, consider: An IPv6-only subscriber must reach an IPv4-only service, but the provider deploys DNS64 alone with no translation path. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Check: Trace a known client flow through DNS resolution, IPv4 or IPv6 encapsulation, translator bindings and return path with packet captures.
- Check: Inspect IS-IS neighbor state, hello capture, interface MTU and level configuration at both endpoints.
- Change: Choose the appropriate IPv6 transition and address-sharing model for subscriber connectivity, and test mapping state and application behavior end to end.
- Change: Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation.
- Enable DNS64 alone and assume it rewrites every required IPv4 header without an actual translator.
Explanation
Correct Answer
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. Required intervention: Choose the appropriate IPv6 transition and address-sharing model for subscriber connectivity, and test mapping state and application behavior end to end.
C: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. Evidence: Trace a known client flow through DNS resolution, IPv4 or IPv6 encapsulation, translator bindings and return path with packet captures.
Incorrect Answers
B:Check: Inspect IS-IS neighbor state, hello capture, interface MTU and level configuration at both endpoints. 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.
D:Change: Choose correct OSPF area behavior and summarization boundaries, confirming permitted external and interarea route propagation. An IPv6-only subscriber must reach an IPv4-only service, but the provider deploys DNS64 alone with no translation path.
E:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. 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.
Question 281
A service provider network engineer is reviewing this backbone or customer-service scenario: A broadband carrier with exhausted IPv4 space adopts DS-Lite but assumes subscriber IPv4 packets traverse the core natively without encapsulation or AFTR processing. A proposed shortcut is: Enable DNS64 alone and assume it rewrites every required IPv4 header without an actual translator. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Choose the appropriate IPv6 transition and address-sharing model for subscriber connectivity, and test mapping state and application behavior end to end.
- Configure high availability features with supported peer behavior and validate which control and forwarding states are preserved during process or RP failure.
- Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary.
- Enable DNS64 alone and assume it rewrites every required IPv4 header without an actual translator.
Explanation
Correct Answer
A:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A broadband carrier with exhausted IPv4 space adopts DS-Lite but assumes subscriber IPv4 packets traverse the core natively without encapsulation or AFTR processing.
Incorrect Answers
B:Configure high availability features with supported peer behavior and validate which control and forwarding states are preserved during process or RP failure. 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.
C:Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary. 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.
D: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. Applied case: A broadband carrier with exhausted IPv4 space adopts DS-Lite but assumes subscriber IPv4 packets traverse the core natively without encapsulation or AFTR processing.
Question 282
A Cisco service provider design review finds: A broadband carrier with exhausted IPv4 space adopts DS-Lite but assumes subscriber IPv4 packets traverse the core natively without encapsulation or AFTR processing. The team proposes: Choose the appropriate IPv6 transition and address-sharing model for subscriber connectivity, and test mapping state and application behavior end to end. 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.
- IS-IS SPF selects routes using cumulative link metrics; wide metric support and consistent advertisements matter in modern core designs.
- Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
- OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior.
Explanation
Correct Answer
A:Demonstrable success requires: Authorized IPv6 and shared-IPv4 applications work with correct port mappings, accountability and predictable failure handling. Applied case: A broadband carrier with exhausted IPv4 space adopts DS-Lite but assumes subscriber IPv4 packets traverse the core natively without encapsulation or AFTR processing.
Incorrect Answers
B:This option addresses a different service provider engineering topic (IS-IS wide metrics and SPF path control) rather than the documented NAT64 CGNAT MAP-T DS-Lite and transition selection decision.
C:Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems. A broadband carrier with exhausted IPv4 space adopts DS-Lite but assumes subscriber IPv4 packets traverse the core natively without encapsulation or AFTR processing.
D:OSPF adjacency formation progresses through distinct neighbor states; matching basic IP addresses does not resolve MTU or designated-router behavior. 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.
Question 283
The service provider operations team has not yet approved a change. Current evidence indicates: A broadband carrier with exhausted IPv4 space adopts DS-Lite but assumes subscriber IPv4 packets traverse the core natively without encapsulation or AFTR processing. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Compare valid path candidates and detailed BGP attributes under a test prefix, then trace which decision criterion breaks the tie.
- Check neighbor state transitions, interface MTU, hello and dead intervals, area type and network type on both peers.
- Compare IS-IS IPv4 and IPv6 LSP TLVs, topology IDs, next-hop tables and controlled ping tests for each family.
- Trace a known client flow through DNS resolution, IPv4 or IPv6 encapsulation, translator bindings and return path with packet captures.
Explanation
Correct Answer
D: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. This check tests the actual routing, transport or service boundary before an operationally risky response.
Incorrect Answers
A:Compare valid path candidates and detailed BGP attributes under a test prefix, then trace which decision criterion breaks the tie. 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.
B:Check neighbor state transitions, interface MTU, hello and dead intervals, area type and network type on both peers. 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.
C:This option addresses a different service provider engineering topic (IS-IS IPv4 IPv6 single and multitopology) rather than the documented NAT64 CGNAT MAP-T DS-Lite and transition selection decision.
Question 284
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A broadband carrier with exhausted IPv4 space adopts DS-Lite but assumes subscriber IPv4 packets traverse the core natively without encapsulation or AFTR processing. 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.
- Authorized prefixes are imported or exported and unintended customer or infrastructure prefixes are rejected without adjacency disruption.
- Authorized IPv6 and shared-IPv4 applications work with correct port mappings, accountability and predictable failure handling.
- Valid alternate paths are visible and traffic shifts within expected service objectives when the primary next hop fails.
- The intended Level-1 or Level-2 adjacency forms and the routers exchange consistent link-state information without dropping required hello traffic.
Explanation
Correct Answer
B: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. The approved implementation step was: Choose the appropriate IPv6 transition and address-sharing model for subscriber connectivity, and test mapping state and application behavior end to end.
Incorrect Answers
A:Authorized prefixes are imported or exported and unintended customer or infrastructure prefixes are rejected without adjacency disruption. 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.
C:Valid alternate paths are visible and traffic shifts within expected service objectives when the primary next hop fails. 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.
D:The intended Level-1 or Level-2 adjacency forms and the routers exchange consistent link-state information without dropping required hello traffic. A broadband carrier with exhausted IPv4 space adopts DS-Lite but assumes subscriber IPv4 packets traverse the core natively without encapsulation or AFTR processing.
Question 285
An implementation sign-off request identifies the following problem: A broadband carrier with exhausted IPv4 space adopts DS-Lite but assumes subscriber IPv4 packets traverse the core natively without encapsulation or AFTR processing. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- Change: Choose documented BGP ingress-traffic engineering signals and verify how relevant peers actually compare received alternatives. Verify: Examine advertised route attributes per peer, remote looking-glass paths and measured ingress flows before and after the change.
- Change: Apply documented BGP community or extended-community policies at the intended import or export point and verify resulting attribute propagation. Verify: Check received and advertised BGP attributes, applied route policy, peer documentation and resulting best path for a controlled test prefix.
- 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: Choose the appropriate IPv6 transition and address-sharing model for subscriber connectivity, and test mapping state and application behavior end to end. Verify: Trace a known client flow through DNS resolution, IPv4 or IPv6 encapsulation, translator bindings and return path with packet captures.
Explanation
Correct Answer
D: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. The change is successful only when: Authorized IPv6 and shared-IPv4 applications work with correct port mappings, accountability and predictable failure handling.
Incorrect Answers
A:Change: Choose documented BGP ingress-traffic engineering signals and verify how relevant peers actually compare received alternatives.
B:Change: Apply documented BGP community or extended-community policies at the intended import or export point and verify resulting attribute propagation. 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.
C:Change: Enable compatible path diversity or BGP PIC mechanisms where supported and verify backup data-plane programming before a failure. 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.
Question 286
A service provider network engineer is reviewing this backbone or customer-service scenario: A service provider performs a route processor switchover and expects zero control-plane churn although the software image does not support session preservation. A proposed shortcut is: Assume a redundant supervisor automatically provides nonstop protocol sessions and unlimited graceful forwarding with no platform configuration. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Configure high availability features with supported peer behavior and validate which control and forwarding states are preserved during process or RP failure.
- Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements.
- Apply documented BGP community or extended-community policies at the intended import or export point and verify resulting attribute propagation.
- Assume a redundant supervisor automatically provides nonstop protocol sessions and unlimited graceful forwarding with no platform configuration.
Explanation
Correct Answer
A:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A service provider performs a route processor switchover and expects zero control-plane churn although the software image does not support session preservation.
Incorrect Answers
B:Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
C:Apply documented BGP community or extended-community policies at the intended import or export point and verify resulting attribute propagation. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
D:Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
Question 287
A Cisco service provider design review finds: A service provider performs a route processor switchover and expects zero control-plane churn although the software image does not support session preservation. The team proposes: Configure high availability features with supported peer behavior and validate which control and forwarding states are preserved during process or RP failure. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
- IS-IS SPF selects routes using cumulative link metrics; wide metric support and consistent advertisements matter in modern core designs.
- IS-IS adjacencies use link-local protocol hellos and compatible level, circuit and network settings; IP reachability alone does not create a neighbor.
- Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
Explanation
Correct Answer
D:Demonstrable success requires: Failure recovery stays within service limits and no stale unvalidated forwarding state persists beyond documented timers. Applied case: A service provider performs a route processor switchover and expects zero control-plane churn although the software image does not support session preservation.
Incorrect Answers
A:BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
B:IS-IS SPF selects routes using cumulative link metrics; wide metric support and consistent advertisements matter in modern core designs. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
C:IS-IS adjacencies use link-local protocol hellos and compatible level, circuit and network settings; IP reachability alone does not create a neighbor. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
Question 288
The service provider operations team has not yet approved a change. Current evidence indicates: A service provider performs a route processor switchover and expects zero control-plane churn although the software image does not support session preservation. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Evaluate a test table with allowed, denied and boundary prefixes against actual show-policy and BGP advertised-routes evidence.
- Check received and advertised BGP attributes, applied route policy, peer documentation and resulting best path for a controlled test prefix.
- Measure neighbor resets, stale route retention, forwarding counters and route processing after a planned RP switchover.
- Inspect IS-IS neighbor state, hello capture, interface MTU and level configuration at both endpoints.
Explanation
Correct Answer
C:Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems. Applied case: A service provider performs a route processor switchover and expects zero control-plane churn although the software image does not support session preservation.
Incorrect Answers
A:Evaluate a test table with allowed, denied and boundary prefixes against actual show-policy and BGP advertised-routes evidence. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
B:Check received and advertised BGP attributes, applied route policy, peer documentation and resulting best path for a controlled test prefix. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
D:Inspect IS-IS neighbor state, hello capture, interface MTU and level configuration at both endpoints. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
Question 289
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A service provider performs a route processor switchover and expects zero control-plane churn although the software image does not support session preservation. 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.
- Stable OSPFv3 adjacencies advertise the intended IPv6 prefixes with reachable next hops.
- Failure recovery stays within service limits and no stale unvalidated forwarding state persists beyond documented timers.
- Only planned prefixes cross the protocol boundary once and core convergence remains stable under service-route churn.
- Preferred paths align with declared metrics while all participating routers interpret the advertised costs consistently.
Explanation
Correct Answer
B:Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems. The result must be validated using the documented device, service or access context.
Incorrect Answers
A:Stable OSPFv3 adjacencies advertise the intended IPv6 prefixes with reachable next hops. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
C:Only planned prefixes cross the protocol boundary once and core convergence remains stable under service-route churn. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
D:Preferred paths align with declared metrics while all participating routers interpret the advertised costs consistently. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
Question 290
For an original SPCOR service-provider engineering scenario, consider: A service provider performs a route processor switchover and expects zero control-plane churn although the software image does not support session preservation. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Change: Apply supported consistent metric style and tune link costs to the provider's intended shortest-path and capacity policy.
- Check: Check neighbor state transitions, interface MTU, hello and dead intervals, area type and network type on both peers.
- Check: Measure neighbor resets, stale route retention, forwarding counters and route processing after a planned RP switchover.
- Change: Configure high availability features with supported peer behavior and validate which control and forwarding states are preserved during process or RP failure.
- Assume a redundant supervisor automatically provides nonstop protocol sessions and unlimited graceful forwarding with no platform configuration.
Explanation
Correct Answer
C:Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems. Acceptance: Failure recovery stays within service limits and no stale unvalidated forwarding state persists beyond documented timers.
D:Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems. Evidence: Measure neighbor resets, stale route retention, forwarding counters and route processing after a planned RP switchover.
Incorrect Answers
A:Change: Apply supported consistent metric style and tune link costs to the provider's intended shortest-path and capacity policy. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
B:Check: Check neighbor state transitions, interface MTU, hello and dead intervals, area type and network type on both peers. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
E:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
