Cisco 350-501 Practice Test 44
Question 430
For an original SPCOR service-provider engineering scenario, consider: An SR-MPLS router loses its primary next hop and waits for full IGP convergence though its topology has a viable postconvergence repair path. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Change: Enable a supported TI-LFA protection mechanism and confirm the repair list is loop-free for the protected link or node failure.
- Change: Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node.
- Check: Compare computed repair SIDs, protected resource, postfailure path and packet-loss duration under a lab failure.
- Use any alternate interface as TI-LFA protection without checking the backup path for loops or failed-resource traversal.
- Check: Trace segment-list execution, SR label stack and the adjacency owner at each hop using a forced parallel-link test.
Explanation
Correct Answer
A:Acceptance: Protected traffic continues through a verified loop-free repair path while IGP converges to a stable new route. Applied case: An SR-MPLS router loses its primary next hop and waits for full IGP convergence though its topology has a viable postconvergence repair path.
C:Acceptance: Protected traffic continues through a verified loop-free repair path while IGP converges to a stable new route. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
Incorrect Answers
B:Change: Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
D:TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure. Use this instead: Enable a supported TI-LFA protection mechanism and confirm the repair list is loop-free for the protected link or node failure.
E:Check: Trace segment-list execution, SR label stack and the adjacency owner at each hop using a forced parallel-link test. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
Question 431
A service provider network engineer is reviewing this backbone or customer-service scenario: An engineer installs an arbitrary SR repair segment list that briefly routes packets back toward the failed link, producing a transient microloop. A proposed shortcut is: Use any alternate interface as TI-LFA protection without checking the backup path for loops or failed-resource traversal. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node.
- Enable a supported TI-LFA protection mechanism and confirm the repair list is loop-free for the protected link or node failure.
- Bind the service steering rule to the correct SR policy color and endpoint and validate candidate preference, segment-list resolution and policy validity.
- Use any alternate interface as TI-LFA protection without checking the backup path for loops or failed-resource traversal.
Explanation
Correct Answer
B:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: An engineer installs an arbitrary SR repair segment list that briefly routes packets back toward the failed link, producing a transient microloop.
Incorrect Answers
A:Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
C:Bind the service steering rule to the correct SR policy color and endpoint and validate candidate preference, segment-list resolution and policy validity. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
D:TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure. Applied case: An engineer installs an arbitrary SR repair segment list that briefly routes packets back toward the failed link, producing a transient microloop.
Question 432
A Cisco service provider design review finds: An engineer installs an arbitrary SR repair segment list that briefly routes packets back toward the failed link, producing a transient microloop. The team proposes: Enable a supported TI-LFA protection mechanism and confirm the repair list is loop-free for the protected link or node failure. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
- A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
- SR traffic engineering policies select candidate paths and instantiate explicit forwarding segments; configuration alone does not prove a policy is active or matched by traffic.
- TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
Explanation
Correct Answer
D:Demonstrable success requires: Protected traffic continues through a verified loop-free repair path while IGP converges to a stable new route. Applied case: An engineer installs an arbitrary SR repair segment list that briefly routes packets back toward the failed link, producing a transient microloop.
Incorrect Answers
A:Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed. An engineer installs an arbitrary SR repair segment list that briefly routes packets back toward the failed link, producing a transient microloop.
B:This option addresses a different service provider engineering topic (PCE-PCC delegation and SRTE path computation) rather than the documented TI-LFA topology-independent loop-free repair decision.
C:SR traffic engineering policies select candidate paths and instantiate explicit forwarding segments; configuration alone does not prove a policy is active or matched by traffic. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
Question 433
The service provider operations team has not yet approved a change. Current evidence indicates: An engineer installs an arbitrary SR repair segment list that briefly routes packets back toward the failed link, producing a transient microloop. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Test link removal, targeted hello maintenance, TCP session state and alternate loopback reachability while measuring session churn.
- Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled.
- Compare computed repair SIDs, protected resource, postfailure path and packet-loss duration under a lab failure.
- Inspect prefix SID TLVs, SRGB advertisements, derived labels and outgoing next hops on at least three routers.
Explanation
Correct Answer
C:Confirm afterward that: Protected traffic continues through a verified loop-free repair path while IGP converges to a stable new route. Applied case: An engineer installs an arbitrary SR repair segment list that briefly routes packets back toward the failed link, producing a transient microloop.
Incorrect Answers
A:Test link removal, targeted hello maintenance, TCP session state and alternate loopback reachability while measuring session churn. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
B:Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
D:Inspect prefix SID TLVs, SRGB advertisements, derived labels and outgoing next hops on at least three routers. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
Question 434
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: An engineer installs an arbitrary SR repair segment list that briefly routes packets back toward the failed link, producing a transient microloop. 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.
- A valid LSP is signaled on capacity-feasible links and impossible reservations are rejected rather than silently oversubscribed.
- Transit and egress forwarding agree with the selected label operation and customer traffic exits at the proper PE without service loss.
- Protected traffic continues through a verified loop-free repair path while IGP converges to a stable new route.
- Remote PEs have resolvable label-switched transport paths through interarea boundaries without flooding all service routes into core IGPs.
Explanation
Correct Answer
C:TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure. The approved implementation step was: Enable a supported TI-LFA protection mechanism and confirm the repair list is loop-free for the protected link or node failure.
Incorrect Answers
A:This option addresses a different service provider engineering topic (RSVP-TE path signaling and reserved bandwidth) rather than the documented TI-LFA topology-independent loop-free repair decision.
B:Transit and egress forwarding agree with the selected label operation and customer traffic exits at the proper PE without service loss. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
D:Remote PEs have resolvable label-switched transport paths through interarea boundaries without flooding all service routes into core IGPs. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
Question 435
An implementation sign-off request identifies the following problem: An engineer installs an arbitrary SR repair segment list that briefly routes packets back toward the failed link, producing a transient microloop. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- Change: Interpret MPLS label operations, bottom-of-stack state and egress handling based on the signaled FEC and selected pop or explicit-null behavior. Verify: Inspect incoming and outgoing labels, label stack operation, TTL and traffic class on a lab LSP with and without explicit-null.
- Change: Enable a supported TI-LFA protection mechanism and confirm the repair list is loop-free for the protected link or node failure. Verify: Compare computed repair SIDs, protected resource, postfailure path and packet-loss duration under a lab failure.
- Change: Verify MPLS forwarding activation, LDP discovery and reachable transport addresses on every required core hop. Verify: Inspect LDP discovery and session state, transport address routing, label binding and hardware forwarding labels along the path.
- Change: Use supported LDP session protection or targeted discovery with routed transport continuity and bounded recovery timers. Verify: Test link removal, targeted hello maintenance, TCP session state and alternate loopback reachability while measuring session churn.
Explanation
Correct Answer
B:The change is successful only when: Protected traffic continues through a verified loop-free repair path while IGP converges to a stable new route.
Incorrect Answers
A:Change: Interpret MPLS label operations, bottom-of-stack state and egress handling based on the signaled FEC and selected pop or explicit-null behavior. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
C:Change: Verify MPLS forwarding activation, LDP discovery and reachable transport addresses on every required core hop.
D:Change: Use supported LDP session protection or targeted discovery with routed transport continuity and bounded recovery timers. TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure.
Question 436
A service provider network engineer is reviewing this backbone or customer-service scenario: A service provider expects a PCE to provision all SR paths but the headend PCC has no valid controller session or delegation status. A proposed shortcut is: Assume a controller dashboard path sketch can program an SRTE router without PCEP connectivity or supported policy delegation. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Establish an authenticated PCE-PCC control relationship, current topology data and valid policy delegation or candidate update handling.
- Use MPLS-aware OAM and label-stack inspection to verify LSP forwarding and localize transport failures separate from ordinary IP reachability.
- Assume a controller dashboard path sketch can program an SRTE router without PCEP connectivity or supported policy delegation.
- Coordinate IGP path eligibility with LDP readiness using supported LDP-IGP synchronization and verify label availability before restoring the path.
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 expects a PCE to provision all SR paths but the headend PCC has no valid controller session or delegation status.
Incorrect Answers
B:Use MPLS-aware OAM and label-stack inspection to verify LSP forwarding and localize transport failures separate from ordinary IP reachability. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
C:A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
D:Coordinate IGP path eligibility with LDP readiness using supported LDP-IGP synchronization and verify label availability before restoring the path. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
Question 437
A Cisco service provider design review finds: A service provider expects a PCE to provision all SR paths but the headend PCC has no valid controller session or delegation status. The team proposes: Establish an authenticated PCE-PCC control relationship, current topology data and valid policy delegation or candidate update handling. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- MPLS core VPN traffic may be blackholed when IGP selects a path before its label transport is operational; LDP synchronization delays cost restoration.
- A global prefix SID expresses reachability toward a node or prefix through IGP shortest path, while an SRGB maps SID indexes into local label values.
- LDP signaling distributes bindings for forwarding equivalence classes, while an IP routing adjacency alone does not prove label transport is ready.
- A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
Explanation
Correct Answer
D:Demonstrable success requires: The headend accepts only valid controller-computed paths and falls back according to defined policy when PCE control is unavailable. Applied case: A service provider expects a PCE to provision all SR paths but the headend PCC has no valid controller session or delegation status.
Incorrect Answers
A:MPLS core VPN traffic may be blackholed when IGP selects a path before its label transport is operational; LDP synchronization delays cost restoration. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
B:This option addresses a different service provider engineering topic (SR-MPLS prefix SID allocation and consistency) rather than the documented PCE-PCC delegation and SRTE path computation decision.
C:LDP signaling distributes bindings for forwarding equivalence classes, while an IP routing adjacency alone does not prove label transport is ready. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
Question 438
The service provider operations team has not yet approved a change. Current evidence indicates: A service provider expects a PCE to provision all SR paths but the headend PCC has no valid controller session or delegation status. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Trace remote PE loopback route and label advertisements through each border node, then validate transport LSP and VPN service forwarding.
- Compare IGP interface cost and SPF route, LDP session progress and LFIB entries during link bounce on each core router.
- Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled.
- Inspect PCEP session state, computed path constraints, delegated policy ownership, SID reachability and actual headend candidate state.
Explanation
Correct Answer
D:A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination. Applied case: A service provider expects a PCE to provision all SR paths but the headend PCC has no valid controller session or delegation status.
Incorrect Answers
A:Trace remote PE loopback route and label advertisements through each border node, then validate transport LSP and VPN service forwarding. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
B:Compare IGP interface cost and SPF route, LDP session progress and LFIB entries during link bounce on each core router. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
C:Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
Question 439
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A service provider expects a PCE to provision all SR paths but the headend PCC has no valid controller session or delegation status. 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 faulty label operation or transit hop is identified and repaired while core IP adjacencies stay stable.
- The headend accepts only valid controller-computed paths and falls back according to defined policy when PCE control is unavailable.
- Remote PEs have resolvable label-switched transport paths through interarea boundaries without flooding all service routes into core IGPs.
- The steered flow crosses the required link and falls back safely if that adjacency is not available.
Explanation
Correct Answer
B:A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination. The result must be validated using the documented device, service or access context.
Incorrect Answers
A:The faulty label operation or transit hop is identified and repaired while core IP adjacencies stay stable. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
C:Remote PEs have resolvable label-switched transport paths through interarea boundaries without flooding all service routes into core IGPs. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
D:The steered flow crosses the required link and falls back safely if that adjacency is not available. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
Question 440
For an original SPCOR service-provider engineering scenario, consider: A service provider expects a PCE to provision all SR paths but the headend PCC has no valid controller session or delegation status. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Assume a controller dashboard path sketch can program an SRTE router without PCEP connectivity or supported policy delegation.
- Change: Interpret MPLS label operations, bottom-of-stack state and egress handling based on the signaled FEC and selected pop or explicit-null behavior.
- Check: Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled.
- Change: Establish an authenticated PCE-PCC control relationship, current topology data and valid policy delegation or candidate update handling.
- Check: Inspect PCEP session state, computed path constraints, delegated policy ownership, SID reachability and actual headend candidate state.
Explanation
Correct Answer
D:A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination. Acceptance: The headend accepts only valid controller-computed paths and falls back according to defined policy when PCE control is unavailable.
E:A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination. Required intervention: Establish an authenticated PCE-PCC control relationship, current topology data and valid policy delegation or candidate update handling.
Incorrect Answers
A:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
B:Change: Interpret MPLS label operations, bottom-of-stack state and egress handling based on the signaled FEC and selected pop or explicit-null behavior. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
C:Check: Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled. A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
