Cisco 350-501 Practice Test 38
Question 370
For an original SPCOR service-provider engineering scenario, consider: A multi-area service provider wants end-to-end labeled transport but only local LDP adjacencies exist and distant PE loopbacks lack consistent label reachability. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Check: Trace remote PE loopback route and label advertisements through each border node, then validate transport LSP and VPN service forwarding.
- Change: Establish an authenticated PCE-PCC control relationship, current topology data and valid policy delegation or candidate update handling.
- Check: Inspect LDP discovery and session state, transport address routing, label binding and hardware forwarding labels along the path.
- Change: Establish end-to-end transport using documented interarea label distribution and BGP labeled-unicast mechanisms where appropriate.
- Assume a plain unlabeled IPv4 route to the distant PE automatically satisfies every cross-domain MPLS VPN label requirement.
Explanation
Correct Answer
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. Required intervention: Establish end-to-end transport using documented interarea label distribution and BGP labeled-unicast mechanisms where appropriate.
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. Acceptance: Remote PEs have resolvable label-switched transport paths through interarea boundaries without flooding all service routes into core IGPs.
Incorrect Answers
B:This option addresses a different service provider engineering topic (PCE-PCC delegation and SRTE path computation) rather than the documented Unified MPLS core and BGP labeled unicast transport decision.
C:Check: Inspect LDP discovery and session state, transport address routing, label binding and hardware forwarding labels along the path. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
E:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
Question 371
A service provider network engineer is reviewing this backbone or customer-service scenario: A region boundary advertises PE prefixes without the needed labeled-unicast transport attributes, causing cross-region VPN services to fail. A proposed shortcut is: Assume a plain unlabeled IPv4 route to the distant PE automatically satisfies every cross-domain MPLS VPN label requirement. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Assume a plain unlabeled IPv4 route to the distant PE automatically satisfies every cross-domain MPLS VPN label requirement.
- Allocate unique intended prefix SID indexes and validate advertised SRGB information and effective labels on participating routers.
- Use supported LDP session protection or targeted discovery with routed transport continuity and bounded recovery timers.
- Establish end-to-end transport using documented interarea label distribution and BGP labeled-unicast mechanisms where appropriate.
Explanation
Correct Answer
D:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A region boundary advertises PE prefixes without the needed labeled-unicast transport attributes, causing cross-region VPN services to fail.
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. Use this instead: Establish end-to-end transport using documented interarea label distribution and BGP labeled-unicast mechanisms where appropriate.
B:Allocate unique intended prefix SID indexes and validate advertised SRGB information and effective labels on participating routers. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
C:Use supported LDP session protection or targeted discovery with routed transport continuity and bounded recovery timers. A region boundary advertises PE prefixes without the needed labeled-unicast transport attributes, causing cross-region VPN services to fail.
Question 372
A Cisco service provider design review finds: A region boundary advertises PE prefixes without the needed labeled-unicast transport attributes, causing cross-region VPN services to fail. The team proposes: Establish end-to-end transport using documented interarea label distribution and BGP labeled-unicast mechanisms where appropriate. 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.
- MPLS LSP ping and traceroute test labeled forwarding equivalence classes and can identify failures hidden behind successful IP control-plane checks.
- RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
- 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
A:Demonstrable success requires: Remote PEs have resolvable label-switched transport paths through interarea boundaries without flooding all service routes into core IGPs. Applied case: A region boundary advertises PE prefixes without the needed labeled-unicast transport attributes, causing cross-region VPN services to fail.
Incorrect Answers
B:MPLS LSP ping and traceroute test labeled forwarding equivalence classes and can identify failures hidden behind successful IP control-plane checks. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
C:RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
D:TI-LFA computes a fast repair path using segment routing and a postconvergence viewpoint to avoid local loops after a topology failure. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
Question 373
The service provider operations team has not yet approved a change. Current evidence indicates: A region boundary advertises PE prefixes without the needed labeled-unicast transport attributes, causing cross-region VPN services to fail. 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.
- Inspect the active candidate, preference, BSID or policy steering rules, operational validity and flow path through the backbone.
- Trace segment-list execution, SR label stack and the adjacency owner at each hop using a forced parallel-link test.
- Inspect prefix SID TLVs, SRGB advertisements, derived labels and outgoing next hops on at least three routers.
Explanation
Correct Answer
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. Applied case: A region boundary advertises PE prefixes without the needed labeled-unicast transport attributes, causing cross-region VPN services to fail.
Incorrect Answers
B:Inspect the active candidate, preference, BSID or policy steering rules, operational validity and flow path through the backbone. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
C:Trace segment-list execution, SR label stack and the adjacency owner at each hop using a forced parallel-link test. A region boundary advertises PE prefixes without the needed labeled-unicast transport attributes, causing cross-region VPN services to fail.
D:Inspect prefix SID TLVs, SRGB advertisements, derived labels and outgoing next hops on at least three routers. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
Question 374
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A region boundary advertises PE prefixes without the needed labeled-unicast transport attributes, causing cross-region VPN services to fail. 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.
- 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.
- Each IPv6 segment resolves to its intended endpoint and traffic crosses SR-MPLS to SRv6 boundaries using supported adaptation.
Explanation
Correct Answer
B:Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed. The result must be validated using the documented device, service or access context.
Incorrect Answers
A:The intended traffic resumes over an eligible repair path within the service convergence target and no protection loop is created. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
C:LDP neighbors become operational on intended links and the requested FEC follows a valid label-switched path end to end. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
D:Each IPv6 segment resolves to its intended endpoint and traffic crosses SR-MPLS to SRv6 boundaries using supported adaptation. A region boundary advertises PE prefixes without the needed labeled-unicast transport attributes, causing cross-region VPN services to fail.
Question 375
An implementation sign-off request identifies the following problem: A region boundary advertises PE prefixes without the needed labeled-unicast transport attributes, causing cross-region VPN services to fail. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- 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: 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: Bind the service steering rule to the correct SR policy color and endpoint and validate candidate preference, segment-list resolution and policy validity. Verify: Inspect the active candidate, preference, BSID or policy steering rules, operational validity and flow path through the backbone.
- Change: Establish end-to-end transport using documented interarea label distribution and BGP labeled-unicast mechanisms where appropriate. Verify: Trace remote PE loopback route and label advertisements through each border node, then validate transport LSP and VPN service forwarding.
Explanation
Correct Answer
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. The change is successful only when: Remote PEs have resolvable label-switched transport paths through interarea boundaries without flooding all service routes into core IGPs.
Incorrect Answers
A:Change: Enable a supported TI-LFA protection mechanism and confirm the repair list is loop-free for the protected link or node failure. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
B:Change: Advertise accurate TE topology and choose a path whose available reservable bandwidth satisfies the RSVP-TE tunnel constraints. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
C:Change: Bind the service steering rule to the correct SR policy color and endpoint and validate candidate preference, segment-list resolution and policy validity. Unified MPLS extends labeled reachability across IGP boundaries while keeping each IGP domain scalable, but label continuity and next-hop resolution must be designed.
Question 376
A service provider network engineer is reviewing this backbone or customer-service scenario: A provider defines an RSVP-TE tunnel with a requested bandwidth larger than every link on its explicit path and expects signaling to succeed. 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.
- 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.
- Request an arbitrarily large reservation and assume a routing shortest path guarantees admission irrespective of bandwidth constraints.
- Use supported LDP session protection or targeted discovery with routed transport continuity and bounded recovery timers.
Explanation
Correct Answer
A:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
Incorrect Answers
B:Establish end-to-end transport using documented interarea label distribution and BGP labeled-unicast mechanisms where appropriate. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
C:RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
D: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.
Question 377
A Cisco service provider design review finds: A provider defines an RSVP-TE tunnel with a requested bandwidth larger than every link on its explicit path and expects signaling to succeed. 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.
- A node SID follows IGP shortest-path semantics, while an adjacency SID identifies a particular link local to its advertising router and must be reached in sequence.
- LDP signaling distributes bindings for forwarding equivalence classes, while an IP routing adjacency alone does not prove label transport is ready.
- RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
- 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
C:Demonstrable success requires: A valid LSP is signaled on capacity-feasible links and impossible reservations are rejected rather than silently oversubscribed. This principle explains the proposed technical approach, which is: Advertise accurate TE topology and choose a path whose available reservable bandwidth satisfies the RSVP-TE tunnel constraints.
Incorrect Answers
A:A node SID follows IGP shortest-path semantics, while an adjacency SID identifies a particular link local to its advertising router and must be reached in sequence. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
B:LDP signaling distributes bindings for forwarding equivalence classes, while an IP routing adjacency alone does not prove label transport is ready. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
D:A Path Computation Element calculates constraints-based paths while the PCC enforces or requests them, and PCEP sessions and delegation govern their coordination. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
Question 378
The service provider operations team has not yet approved a change. Current evidence indicates: A provider defines an RSVP-TE tunnel with a requested bandwidth larger than every link on its explicit path and expects signaling to succeed. 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.
- Inspect incoming and outgoing labels, label stack operation, TTL and traffic class on a lab LSP with and without explicit-null.
- Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled.
- Check TE database attributes, unreserved bandwidth, ERO or path message and reservation errors across the candidate hops.
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. Confirm afterward that: A valid LSP is signaled on capacity-feasible links and impossible reservations are rejected rather than silently oversubscribed.
Incorrect Answers
A:Trace remote PE loopback route and label advertisements through each border node, then validate transport LSP and VPN service forwarding. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
B:Inspect incoming and outgoing labels, label stack operation, TTL and traffic class on a lab LSP with and without explicit-null. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
C:Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
Question 379
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A provider defines an RSVP-TE tunnel with a requested bandwidth larger than every link on its explicit path and expects signaling to succeed. 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.
- Protected traffic continues through a verified loop-free repair path while IGP converges to a stable new route.
- A valid LSP is signaled on capacity-feasible links and impossible reservations are rejected rather than silently oversubscribed.
- LDP neighbors become operational on intended links and the requested FEC follows a valid label-switched path end to end.
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. 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. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
B:This option addresses a different service provider engineering topic (TI-LFA topology-independent loop-free repair) rather than the documented RSVP-TE path signaling and reserved bandwidth decision.
D:LDP neighbors become operational on intended links and the requested FEC follows a valid label-switched path end to end. RSVP-TE establishes signaled label-switched paths using path and reservation messages, while IGP TE extensions distribute topology constraints for computation.
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.
