Cisco 350-501 Practice Test 40
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.
Question 391
A service provider network engineer is reviewing this backbone or customer-service scenario: An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node. 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.
- 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.
- Verify MPLS forwarding activation, LDP discovery and reachable transport addresses on every required core hop.
- Bind the service steering rule to the correct SR policy color and endpoint and validate candidate preference, segment-list resolution and policy validity.
Explanation
Correct Answer
A:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node.
Incorrect Answers
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. Use this instead: Configure supported RSVP local protection mechanisms and verify that a prepared bypass or detour can protect the intended link or node.
C:Verify MPLS forwarding activation, LDP discovery and reachable transport addresses on every required core hop. 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:Bind the service steering rule to the correct SR policy color and endpoint and validate candidate preference, segment-list resolution and policy validity. 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 392
A Cisco service provider design review finds: An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node. 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.
- MPLS core VPN traffic may be blackholed when IGP selects a path before its label transport is operational; LDP synchronization delays cost restoration.
- 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.
- MPLS TE fast reroute preestablishes backup forwarding or signaling so a point of local repair can redirect LSP traffic quickly after a protected failure.
- SRv6 encodes endpoint functions in IPv6 SIDs and uSID compresses supported behavior sequences; interworking gateways translate service or transport context between domains.
Explanation
Correct Answer
C:Demonstrable success requires: The intended traffic resumes over an eligible repair path within the service convergence target and no protection loop is created. Applied case: An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node.
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. 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: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. 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:SRv6 encodes endpoint functions in IPv6 SIDs and uSID compresses supported behavior sequences; interworking gateways translate service or transport context between domains. 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 393
The service provider operations team has not yet approved a change. Current evidence indicates: An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node. 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.
- Check IPv6 locator advertisements, SID behavior, encapsulation and decapsulation and gateway forwarding for a test VPN or steered flow.
- Inspect prefix SID TLVs, SRGB advertisements, derived labels and outgoing next hops on at least three routers.
- Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled.
Explanation
Correct Answer
D: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: An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node.
Incorrect Answers
A:Test link removal, targeted hello maintenance, TCP session state and alternate loopback reachability while measuring session churn. An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node.
B:Check IPv6 locator advertisements, SID behavior, encapsulation and decapsulation and gateway forwarding for a test VPN or steered flow. 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:Inspect prefix SID TLVs, SRGB advertisements, derived labels and outgoing next hops on at least three 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.
Question 394
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node. 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.
- Traffic does not migrate onto the recovered path until a valid label-switched transport is available.
- The intended traffic resumes over an eligible repair path within the service convergence target and no protection loop is created.
- A valid LSP is signaled on capacity-feasible links and impossible reservations are rejected rather than silently oversubscribed.
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. 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. An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node.
B:Traffic does not migrate onto the recovered path until a valid label-switched transport is available. An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node.
D:A valid LSP is signaled on capacity-feasible links and impossible reservations are rejected rather than silently oversubscribed. An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node.
Question 395
An implementation sign-off request identifies the following problem: An engineer enables generic IP ECMP and claims every RSVP-TE LSP has pre-signaled local protection across a failing node. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- 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: 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: 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: Establish an authenticated PCE-PCC control relationship, current topology data and valid policy delegation or candidate update handling. Verify: Inspect PCEP session state, computed path constraints, delegated policy ownership, SID reachability and actual headend candidate state.
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 change is successful only when: The intended traffic resumes over an eligible repair path within the service convergence target and no protection loop is created.
Incorrect Answers
B:Change: Coordinate IGP path eligibility with LDP readiness using supported LDP-IGP synchronization and verify label availability before restoring 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.
C:This option addresses a different service provider engineering topic (TI-LFA topology-independent loop-free repair) rather than the documented RSVP TE fast reroute and local protection decision.
D:Change: Establish an authenticated PCE-PCC control relationship, current topology data and valid policy delegation or candidate update 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.
Question 396
A service provider network engineer is reviewing this backbone or customer-service scenario: Two core routers advertise the same global prefix SID index for different prefixes, creating inconsistent label meaning across the SR domain. A proposed shortcut is: Assign arbitrary overlapping prefix SID indexes and treat the numeric label as globally identical across routers with different SRGBs. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Allocate routable SRv6 locators and supported endpoint behaviors and design explicit interworking for differing SR data planes.
- Allocate unique intended prefix SID indexes and validate advertised SRGB information and effective labels on participating routers.
- Verify MPLS forwarding activation, LDP discovery and reachable transport addresses on every required core hop.
- Assign arbitrary overlapping prefix SID indexes and treat the numeric label as globally identical across routers with different SRGBs.
Explanation
Correct Answer
B:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. 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.
Incorrect Answers
A:Allocate routable SRv6 locators and supported endpoint behaviors and design explicit interworking for differing SR data planes. 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.
C:Verify MPLS forwarding activation, LDP discovery and reachable transport addresses on every required core hop. 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.
D: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. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
Question 397
A Cisco service provider design review finds: Two core routers advertise the same global prefix SID index for different prefixes, creating inconsistent label meaning across the SR domain. The team proposes: Allocate unique intended prefix SID indexes and validate advertised SRGB information and effective labels on participating routers. 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.
- 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.
- MPLS core VPN traffic may be blackholed when IGP selects a path before its label transport is operational; LDP synchronization delays cost restoration.
- 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
B:Demonstrable success requires: Every router resolves the intended prefix SID consistently and traffic reaches the target node via the valid SR transport. This principle explains the proposed technical approach, which is: Allocate unique intended prefix SID indexes and validate advertised SRGB information and effective labels on participating routers.
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. 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.
C: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.
D:This option addresses a different service provider engineering topic (TI-LFA topology-independent loop-free repair) rather than the documented SR-MPLS prefix SID allocation and consistency decision.
Question 398
The service provider operations team has not yet approved a change. Current evidence indicates: Two core routers advertise the same global prefix SID index for different prefixes, creating inconsistent label meaning across the SR domain. 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.
- Test link removal, targeted hello maintenance, TCP session state and alternate loopback reachability while measuring session churn.
- Inspect incoming and outgoing labels, label stack operation, TTL and traffic class on a lab LSP with and without explicit-null.
- Inspect prefix SID TLVs, SRGB advertisements, derived labels and outgoing next hops on at least three routers.
Explanation
Correct Answer
D: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. Applied case: Two core routers advertise the same global prefix SID index for different prefixes, creating inconsistent label meaning across the SR domain.
Incorrect Answers
A:Check TE database attributes, unreserved bandwidth, ERO or path message and reservation errors across the candidate hops. 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.
B:Test link removal, targeted hello maintenance, TCP session state and alternate loopback reachability while measuring session churn. 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.
C:Inspect incoming and outgoing labels, label stack operation, TTL and traffic class on a lab LSP with and without explicit-null. 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.
Question 399
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: Two core routers advertise the same global prefix SID index for different prefixes, creating inconsistent label meaning across the SR domain. 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.
- LDP neighbors become operational on intended links and the requested FEC follows a valid label-switched path end to end.
- Every router resolves the intended prefix SID consistently and traffic reaches the target node via the valid SR transport.
- The headend accepts only valid controller-computed paths and falls back according to defined policy when PCE control is unavailable.
Explanation
Correct Answer
C: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. 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. 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.
B:LDP neighbors become operational on intended links and the requested FEC follows a valid label-switched path end to end. 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.
D:The headend accepts only valid controller-computed paths and falls back according to defined policy when PCE control is unavailable. 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.
Question 400
For an original SPCOR service-provider engineering scenario, consider: Two core routers advertise the same global prefix SID index for different prefixes, creating inconsistent label meaning across the SR domain. Select THREE compatible elements: a proper correction, a targeted diagnostic and an acceptance result.
- Check: Inspect prefix SID TLVs, SRGB advertisements, derived labels and outgoing next hops on at least three routers.
- Change: Combine node and adjacency SIDs in a segment list with proper endpoint locality and imposed stack depth for an explicit steering requirement.
- Change: Allocate unique intended prefix SID indexes and validate advertised SRGB information and effective labels on participating routers.
- Check: Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled.
- Result: Every router resolves the intended prefix SID consistently and traffic reaches the target node via the valid SR transport.
- Result: Traffic does not migrate onto the recovered path until a valid label-switched transport is available.
Explanation
Correct Answer
A: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. Required intervention: Allocate unique intended prefix SID indexes and validate advertised SRGB information and effective labels on participating routers.
C: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. Evidence: Inspect prefix SID TLVs, SRGB advertisements, derived labels and outgoing next hops on at least three routers.
E: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. Result: Every router resolves the intended prefix SID consistently and traffic reaches the target node via the valid SR transport.
Incorrect Answers
B:Change: Combine node and adjacency SIDs in a segment list with proper endpoint locality and imposed stack depth for an explicit steering requirement. 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.
D:Check: Inspect protected interface and facility state, bypass path validity and measured traffic loss when the link or node is disabled. 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.
F:Result: Traffic does not migrate onto the recovered path until a valid label-switched transport is available. 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.
