Cisco 350-501 Practice Test 39
Question 380
For an original SPCOR service-provider engineering scenario, consider: A provider defines an RSVP-TE tunnel with a requested bandwidth larger than every link on its explicit path and expects signaling to succeed. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Change: Use supported LDP session protection or targeted discovery with routed transport continuity and bounded recovery timers.
- Check: Check IPv6 locator advertisements, SID behavior, encapsulation and decapsulation and gateway forwarding for a test VPN or steered flow.
- Change: Advertise accurate TE topology and choose a path whose available reservable bandwidth satisfies the RSVP-TE tunnel constraints.
- Check: Check TE database attributes, unreserved bandwidth, ERO or path message and reservation errors across the candidate hops.
- Request an arbitrarily large reservation and assume a routing shortest path guarantees admission irrespective of bandwidth constraints.
Explanation
Correct Answer
C:RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation. Acceptance: A valid LSP is signaled on capacity-feasible links and impossible reservations are rejected rather than silently oversubscribed.
D:RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation. Applied case: A provider defines an RSVP-TE tunnel with a requested bandwidth larger than every link on its explicit path and expects signaling to succeed.
Incorrect Answers
A:Change: Use supported LDP session protection or targeted discovery with routed transport continuity and bounded recovery timers. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
B:Check: Check IPv6 locator advertisements, SID behavior, encapsulation and decapsulation and gateway forwarding for a test VPN or steered flow. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
E:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
Question 381
A service provider network engineer is reviewing this backbone or customer-service scenario: A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions. A proposed shortcut is: Request an arbitrarily large reservation and assume a routing shortest path guarantees admission irrespective of bandwidth constraints. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Request an arbitrarily large reservation and assume a routing shortest path guarantees admission irrespective of bandwidth constraints.
- Advertise accurate TE topology and choose a path whose available reservable bandwidth satisfies the RSVP-TE tunnel constraints.
- Establish end-to-end transport using documented interarea label distribution and BGP labeled-unicast mechanisms where appropriate.
- Establish an authenticated PCE-PCC control relationship, current topology data and valid policy delegation or candidate update handling.
Explanation
Correct Answer
B:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions.
Incorrect Answers
A:RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation. Applied case: A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions.
C:Establish end-to-end transport using documented interarea label distribution and BGP labeled-unicast mechanisms where appropriate. A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions.
D:Establish an authenticated PCE-PCC control relationship, current topology data and valid policy delegation or candidate update handling. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
Question 382
A Cisco service provider design review finds: A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions. The team proposes: Advertise accurate TE topology and choose a path whose available reservable bandwidth satisfies the RSVP-TE tunnel constraints. 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.
- RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
- Penultimate-hop popping removes the outer transport label before egress, while explicit-null retains a label where required for policy or QoS handling.
- Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
Explanation
Correct Answer
B:Demonstrable success requires: A valid LSP is signaled on capacity-feasible links and impossible reservations are rejected rather than silently oversubscribed. Applied case: A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions.
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. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
C:Penultimate-hop popping removes the outer transport label before egress, while explicit-null retains a label where required for policy or QoS handling. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
D:Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
Question 383
The service provider operations team has not yet approved a change. Current evidence indicates: A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Check TE database attributes, unreserved bandwidth, ERO or path message and reservation errors across the candidate hops.
- Inspect the active candidate, preference, BSID or policy steering rules, operational validity and flow path through the backbone.
- Inspect incoming and outgoing labels, label stack operation, TTL and traffic class on a lab LSP with and without explicit-null.
- Check IPv6 locator advertisements, SID behavior, encapsulation and decapsulation and gateway forwarding for a test VPN or steered flow.
Explanation
Correct Answer
A:RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation. This check tests the actual routing, transport or service boundary before an operationally risky response.
Incorrect Answers
B:Inspect the active candidate, preference, BSID or policy steering rules, operational validity and flow path through the backbone. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
C:Inspect incoming and outgoing labels, label stack operation, TTL and traffic class on a lab LSP with and without explicit-null. A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions.
D:Check IPv6 locator advertisements, SID behavior, encapsulation and decapsulation and gateway forwarding for a test VPN or steered flow. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
Question 384
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions. 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.
- Remote PEs have resolvable label-switched transport paths through interarea boundaries without flooding all service routes into core IGPs.
- LDP neighbors become operational on intended links and the requested FEC follows a valid label-switched path end to end.
- A valid LSP is signaled on capacity-feasible links and impossible reservations are rejected rather than silently oversubscribed.
Explanation
Correct Answer
D:RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation. The approved implementation step was: Advertise accurate TE topology and choose a path whose available reservable bandwidth satisfies the RSVP-TE tunnel constraints.
Incorrect Answers
A:The faulty label operation or transit hop is identified and repaired while core IP adjacencies stay stable. A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions.
B:Remote PEs have resolvable label-switched transport paths through interarea boundaries without flooding all service routes into core IGPs. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
C:LDP neighbors become operational on intended links and the requested FEC follows a valid label-switched path end to end. A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions.
Question 385
An implementation sign-off request identifies the following problem: A traffic-engineered LSP fails at the headend because the required TE topology attributes are not advertised by the IGP extensions. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- Change: Coordinate IGP path eligibility with LDP readiness using supported LDP-IGP synchronization and verify label availability before restoring the path. Verify: Compare IGP interface cost and SPF route, LDP session progress and LFIB entries during link bounce on each core router.
- Change: Advertise accurate TE topology and choose a path whose available reservable bandwidth satisfies the RSVP-TE tunnel constraints. Verify: Check TE database attributes, unreserved bandwidth, ERO or path message and reservation errors across the candidate hops.
- Change: Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node. Verify: Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled.
- Change: Combine node and adjacency SIDs in a segment list with proper endpoint locality and imposed stack depth for an explicit steering requirement. Verify: Trace segment-list execution, SR label stack and the adjacency owner at each hop using a forced parallel-link test.
Explanation
Correct Answer
B:RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation. The change is successful only when: A valid LSP is signaled on capacity-feasible links and impossible reservations are rejected rather than silently oversubscribed.
Incorrect Answers
A:Change: Coordinate IGP path eligibility with LDP readiness using supported LDP-IGP synchronization and verify label availability before restoring the path. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
C:Change: Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
D:Change: Combine node and adjacency SIDs in a segment list with proper endpoint locality and imposed stack depth for an explicit steering requirement. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
Question 386
A service provider network engineer is reviewing this backbone or customer-service scenario: A protected transport tunnel reroutes slowly after a backbone link fails because no valid local backup path was prepared at the point of failure. A proposed shortcut is: Assume any IGP alternate route instantly provides RSVP-TE local repair for all tunnels without preprovisioning. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Combine node and adjacency SIDs in a segment list with proper endpoint locality and imposed stack depth for an explicit steering requirement.
- Assume any IGP alternate route instantly provides RSVP-TE local repair for all tunnels without preprovisioning.
- Establish end-to-end transport using documented interarea label distribution and BGP labeled-unicast mechanisms where appropriate.
- Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node.
Explanation
Correct Answer
D:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A protected transport tunnel reroutes slowly after a backbone link fails because no valid local backup path was prepared at the point of failure.
Incorrect Answers
A:Combine node and adjacency SIDs in a segment list with proper endpoint locality and imposed stack depth for an explicit steering requirement. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
B:MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
C:Establish end-to-end transport using documented interarea label distribution and BGP labeled-unicast mechanisms where appropriate. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
Question 387
A Cisco service provider design review finds: A protected transport tunnel reroutes slowly after a backbone link fails because no valid local backup path was prepared at the point of failure. The team proposes: Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination.
- MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
- Penultimate-hop popping removes the outer transport label before egress, while explicit-null retains a label where required for policy or QoS handling.
- LDP signaling distributes bindings for forwarding equivalence classes, while an IP routing adjacency alone does not prove label transport is ready.
Explanation
Correct Answer
B:Demonstrable success requires: The intended traffic resumes over an eligible repair path within the service convergence target and no protection loop is created. This principle explains the proposed technical approach, which is: Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node.
Incorrect Answers
A:A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
C:Penultimate-hop popping removes the outer transport label before egress, while explicit-null retains a label where required for policy or QoS handling. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
D:LDP signaling distributes bindings for forwarding equivalence classes, while an IP routing adjacency alone does not prove label transport is ready. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
Question 388
The service provider operations team has not yet approved a change. Current evidence indicates: A protected transport tunnel reroutes slowly after a backbone link fails because no valid local backup path was prepared at the point of failure. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Inspect incoming and outgoing labels, label stack operation, TTL and traffic class on a lab LSP with and without explicit-null.
- Trace segment-list execution, SR label stack and the adjacency owner at each hop using a forced parallel-link test.
- Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled.
- Compare IGP interface cost and SPF route, LDP session progress and LFIB entries during link bounce on each core router.
Explanation
Correct Answer
C:MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure. Applied case: A protected transport tunnel reroutes slowly after a backbone link fails because no valid local backup path was prepared at the point of failure.
Incorrect Answers
A:Inspect incoming and outgoing labels, label stack operation, TTL and traffic class on a lab LSP with and without explicit-null. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
B:Trace segment-list execution, SR label stack and the adjacency owner at each hop using a forced parallel-link test. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
D:Compare IGP interface cost and SPF route, LDP session progress and LFIB entries during link bounce on each core router. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
Question 389
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A protected transport tunnel reroutes slowly after a backbone link fails because no valid local backup path was prepared at the point of failure. 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 intended traffic resumes over an eligible repair path within the service convergence target and no protection loop is created.
- Targeted traffic follows the active approved policy and reacts predictably when the selected candidate becomes invalid.
- Traffic does not migrate onto the recovered path until a valid label-switched transport is available.
- Remote PEs have resolvable label-switched transport paths through interarea boundaries without flooding all service routes into core IGPs.
Explanation
Correct Answer
A:MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure. The approved implementation step was: Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node.
Incorrect Answers
B:Targeted traffic follows the active approved policy and reacts predictably when the selected candidate becomes invalid. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
C:Traffic does not migrate onto the recovered path until a valid label-switched transport is available. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
D:Remote PEs have resolvable label-switched transport paths through interarea boundaries without flooding all service routes into core IGPs. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
Question 390
For an original SPCOR service-provider engineering scenario, consider: A protected transport tunnel reroutes slowly after a backbone link fails because no valid local backup path was prepared at the point of failure. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Check: Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled.
- Check: Inspect LDP discovery and session state, transport address routing, label binding and hardware forwarding labels along the path.
- Change: Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node.
- Assume any IGP alternate route instantly provides RSVP-TE local repair for all tunnels without preprovisioning.
- Change: Allocate unique intended prefix SID indexes and validate advertised SRGB information and effective labels on participating routers.
Explanation
Correct Answer
A:MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure. Required intervention: Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node.
C:MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure. Evidence: Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled.
Incorrect Answers
B:Check: Inspect LDP discovery and session state, transport address routing, label binding and hardware forwarding labels along the path. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
D:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
E:Change: Allocate unique intended prefix SID indexes and validate advertised SRGB information and effective labels on participating routers. MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
