Cisco 350-501 Practice Test 50
Question 490
For an original SPCOR service-provider engineering scenario, consider: A wholesale provider carries another carrier's VPN traffic but accidentally imports every downstream customer VRF into the core IGP instead of creating scalable labeled transit. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Change: Build the supported carrier-supporting-carrier transport and routing boundary, retaining customer-carrier control where intended and validating labeled reachability.
- Flood the downstream carrier's complete customer service table into every provider core router as an obligatory transit step.
- Check: Check labeled route handoff, VRF or transport separation, next-hop reachability and a representative downstream customer LSP.
- Change: Configure consistent service and customer VLAN tag handling with explicit encapsulation and correct cross-PE mapping.
- Check: Trace VPNv4 advertisements, ASBR or RR roles, per-hop label stack and route-target import on a two-AS test topology.
Explanation
Correct Answer
A:Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route. Acceptance: The customer carrier preserves its own service topology while the backbone transports authorized labeled traffic without core route explosion.
C:Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route. Required intervention: Build the supported carrier-supporting-carrier transport and routing boundary, retaining customer-carrier control where intended and validating labeled reachability.
Incorrect Answers
B:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route.
D:Change: Configure consistent service and customer VLAN tag handling with explicit encapsulation and correct cross-PE mapping. Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route.
E:Check: Trace VPNv4 advertisements, ASBR or RR roles, per-hop label stack and route-target import on a two-AS test topology. Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route.
Question 491
A service provider network engineer is reviewing this backbone or customer-service scenario: A customer carrier expects end-to-end MPLS labels across the upstream backbone but the transit PE strips the necessary labeled forwarding context at the boundary. A proposed shortcut is: Flood the downstream carrier's complete customer service table into every provider core router as an obligatory transit step. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Flood the downstream carrier's complete customer service table into every provider core router as an obligatory transit step.
- Build the supported carrier-supporting-carrier transport and routing boundary, retaining customer-carrier control where intended and validating labeled reachability.
- Configure consistent service and customer VLAN tag handling with explicit encapsulation and correct cross-PE mapping.
- Select the supported Inter-AS VPN option and validate labeled VPN route exchange, route targets and transport next-hop resolution at each boundary.
Explanation
Correct Answer
B:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A customer carrier expects end-to-end MPLS labels across the upstream backbone but the transit PE strips the necessary labeled forwarding context at the boundary.
Incorrect Answers
A:Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route. Use this instead: Build the supported carrier-supporting-carrier transport and routing boundary, retaining customer-carrier control where intended and validating labeled reachability.
C:Configure consistent service and customer VLAN tag handling with explicit encapsulation and correct cross-PE mapping. A customer carrier expects end-to-end MPLS labels across the upstream backbone but the transit PE strips the necessary labeled forwarding context at the boundary.
D:Select the supported Inter-AS VPN option and validate labeled VPN route exchange, route targets and transport next-hop resolution at each boundary. Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route.
Question 492
A Cisco service provider design review finds: A customer carrier expects end-to-end MPLS labels across the upstream backbone but the transit PE strips the necessary labeled forwarding context at the boundary. The team proposes: Build the supported carrier-supporting-carrier transport and routing boundary, retaining customer-carrier control where intended and validating labeled reachability. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- IEEE 802.1ad provider bridging adds a service tag outside customer VLAN tags, and tag roles must remain consistent through the carrier network.
- Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route.
- Inter-AS L3VPN designs extend VPN signaling across AS boundaries with option-specific control-plane and label requirements; route visibility does not alone prove data-plane continuity.
- EVPN multihoming coordinates PE participation through Ethernet segment routes and forwarder election to prevent loops and maintain reachability.
Explanation
Correct Answer
B:Demonstrable success requires: The customer carrier preserves its own service topology while the backbone transports authorized labeled traffic without core route explosion. Applied case: A customer carrier expects end-to-end MPLS labels across the upstream backbone but the transit PE strips the necessary labeled forwarding context at the boundary.
Incorrect Answers
A:IEEE 802.1ad provider bridging adds a service tag outside customer VLAN tags, and tag roles must remain consistent through the carrier network. A customer carrier expects end-to-end MPLS labels across the upstream backbone but the transit PE strips the necessary labeled forwarding context at the boundary.
C:Inter-AS L3VPN designs extend VPN signaling across AS boundaries with option-specific control-plane and label requirements; route visibility does not alone prove data-plane continuity. Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route.
D:This option addresses a different service provider engineering topic (EVPN multihoming Ethernet segment and split horizon) rather than the documented Carrier supporting carrier hierarchical VPN transport decision.
Question 493
The service provider operations team has not yet approved a change. Current evidence indicates: A customer carrier expects end-to-end MPLS labels across the upstream backbone but the transit PE strips the necessary labeled forwarding context at the boundary. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Capture ingress and egress Ethernet frames including TPID, tag stack and VLAN IDs for two isolated customers.
- Inspect IGMPv3 source lists or MLD reports, snooping table, receiver membership and forwarded multicast stream source identities.
- Inspect (*,G) and (S,G) state, RP mapping, RPF interface and actual receiver joins under a test stream.
- Check labeled route handoff, VRF or transport separation, next-hop reachability and a representative downstream customer LSP.
Explanation
Correct Answer
D:Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route. Applied case: A customer carrier expects end-to-end MPLS labels across the upstream backbone but the transit PE strips the necessary labeled forwarding context at the boundary.
Incorrect Answers
A:Capture ingress and egress Ethernet frames including TPID, tag stack and VLAN IDs for two isolated customers. A customer carrier expects end-to-end MPLS labels across the upstream backbone but the transit PE strips the necessary labeled forwarding context at the boundary.
B:Inspect IGMPv3 source lists or MLD reports, snooping table, receiver membership and forwarded multicast stream source identities. Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route.
C:This option addresses a different service provider engineering topic (PIM sparse-mode SSM and rendezvous-point behavior) rather than the documented Carrier supporting carrier hierarchical VPN transport decision.
Question 494
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A customer carrier expects end-to-end MPLS labels across the upstream backbone but the transit PE strips the necessary labeled forwarding context at the boundary. 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.
- Subscribers receive only authorized group and source traffic with no unnecessary replication to idle access ports.
- Permitted locations communicate according to the contracted Ethernet service while disallowed leaf or tenant pairs remain isolated.
- The customer carrier preserves its own service topology while the backbone transports authorized labeled traffic without core route explosion.
- High-priority services meet policy while excess traffic is bounded and ordinary customer classes retain their contracted forwarding share.
Explanation
Correct Answer
C:Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route. The result must be validated using the documented device, service or access context.
Incorrect Answers
A:Subscribers receive only authorized group and source traffic with no unnecessary replication to idle access ports. Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route.
B:Permitted locations communicate according to the contracted Ethernet service while disallowed leaf or tenant pairs remain isolated. Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route.
D:This option addresses a different service provider engineering topic (QoS classification marking policing shaping and WRED) rather than the documented Carrier supporting carrier hierarchical VPN transport decision.
Question 495
An implementation sign-off request identifies the following problem: A customer carrier expects end-to-end MPLS labels across the upstream backbone but the transit PE strips the necessary labeled forwarding context at the boundary. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- Change: Use matching IGMP or MLD listener protocols and supported source-filtering behavior on the appropriate IPv4 or IPv6 access segment. Verify: Inspect IGMPv3 source lists or MLD reports, snooping table, receiver membership and forwarded multicast stream source identities.
- Change: Build the supported carrier-supporting-carrier transport and routing boundary, retaining customer-carrier control where intended and validating labeled reachability. Verify: Check labeled route handoff, VRF or transport separation, next-hop reachability and a representative downstream customer LSP.
- Change: Advertise and import the proper EVPN MAC or IP reachability route type and associated route targets for the requested L2 or L3 service. Verify: Check EVPN address-family advertisements, route types, Ethernet segment and EVI context, route targets and remote forwarding database.
- Change: Select the supported Inter-AS VPN option and validate labeled VPN route exchange, route targets and transport next-hop resolution at each boundary. Verify: Trace VPNv4 advertisements, ASBR or RR roles, per-hop label stack and route-target import on a two-AS test topology.
Explanation
Correct Answer
B:Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route. The change is successful only when: The customer carrier preserves its own service topology while the backbone transports authorized labeled traffic without core route explosion.
Incorrect Answers
A:Change: Use matching IGMP or MLD listener protocols and supported source-filtering behavior on the appropriate IPv4 or IPv6 access segment.
C:Change: Advertise and import the proper EVPN MAC or IP reachability route type and associated route targets for the requested L2 or L3 service.
D:Change: Select the supported Inter-AS VPN option and validate labeled VPN route exchange, route targets and transport next-hop resolution at each boundary.
Question 496
A service provider network engineer is reviewing this backbone or customer-service scenario: A customer's multicast video stream crosses an MPLS VPN but the provider builds only unicast VRF routes and expects replication to happen automatically. A proposed shortcut is: Treat every unicast VPN route as an automatic request for multicast delivery to all provider edge routers. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Treat every unicast VPN route as an automatic request for multicast delivery to all provider edge routers.
- Advertise and import the proper EVPN MAC or IP reachability route type and associated route targets for the requested L2 or L3 service.
- Configure a consistent Ethernet Segment Identifier and supported designated-forwarder or split-horizon behavior for the multihoming model.
- Configure the supported mVPN multicast control-plane and provider transport distribution according to receiver membership and traffic scale.
Explanation
Correct Answer
D:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A customer's multicast video stream crosses an MPLS VPN but the provider builds only unicast VRF routes and expects replication to happen automatically.
Incorrect Answers
A:MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
B:Advertise and import the proper EVPN MAC or IP reachability route type and associated route targets for the requested L2 or L3 service. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
C:Configure a consistent Ethernet Segment Identifier and supported designated-forwarder or split-horizon behavior for the multihoming model. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
Question 497
A Cisco service provider design review finds: A customer's multicast video stream crosses an MPLS VPN but the provider builds only unicast VRF routes and expects replication to happen automatically. The team proposes: Configure the supported mVPN multicast control-plane and provider transport distribution according to receiver membership and traffic scale. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- EVPN uses MP-BGP to signal Ethernet MAC or IP reachability and other service state; type-2 and type-5 serve different reachability functions.
- Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route.
- MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
- L3VPN extranet services require controlled cross-VRF routing and return reachability; sharing a few service routes need not grant full tenant-to-tenant visibility.
Explanation
Correct Answer
C:Demonstrable success requires: Only authorized receiving VPN sites get the multicast data and replication uses the intended provider transport resources. Applied case: A customer's multicast video stream crosses an MPLS VPN but the provider builds only unicast VRF routes and expects replication to happen automatically.
Incorrect Answers
A:EVPN uses MP-BGP to signal Ethernet MAC or IP reachability and other service state; type-2 and type-5 serve different reachability functions. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
B:Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
D:L3VPN extranet services require controlled cross-VRF routing and return reachability; sharing a few service routes need not grant full tenant-to-tenant visibility. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
Question 498
The service provider operations team has not yet approved a change. Current evidence indicates: A customer's multicast video stream crosses an MPLS VPN but the provider builds only unicast VRF routes and expects replication to happen automatically. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Check labeled route handoff, VRF or transport separation, next-hop reachability and a representative downstream customer LSP.
- Inspect ring protection state, OAM continuity-check results, link-failure events and convergence on one forced-ring break.
- Inspect IGMPv3 source lists or MLD reports, snooping table, receiver membership and forwarded multicast stream source identities.
- Inspect customer PIM state, mVPN BGP or tree signaling, receiver joins, replication counters and stream reachability between PEs.
Explanation
Correct Answer
D:Confirm afterward that: Only authorized receiving VPN sites get the multicast data and replication uses the intended provider transport resources. Applied case: A customer's multicast video stream crosses an MPLS VPN but the provider builds only unicast VRF routes and expects replication to happen automatically.
Incorrect Answers
A:Check labeled route handoff, VRF or transport separation, next-hop reachability and a representative downstream customer LSP. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
B:Inspect ring protection state, OAM continuity-check results, link-failure events and convergence on one forced-ring break. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
C:Inspect IGMPv3 source lists or MLD reports, snooping table, receiver membership and forwarded multicast stream source identities. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
Question 499
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A customer's multicast video stream crosses an MPLS VPN but the provider builds only unicast VRF routes and expects replication to happen automatically. 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.
- Customers reach only approved shared services and internet egress while peer-to-peer tenant access remains restricted.
- High-priority services meet policy while excess traffic is bounded and ordinary customer classes retain their contracted forwarding share.
- Only authorized receiving VPN sites get the multicast data and replication uses the intended provider transport resources.
- Only authorized customer VPNs extend between providers and payload forwarding follows a valid label-switched or agreed interconnect path.
Explanation
Correct Answer
C:MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange. Applied case: A customer's multicast video stream crosses an MPLS VPN but the provider builds only unicast VRF routes and expects replication to happen automatically.
Incorrect Answers
A:Customers reach only approved shared services and internet egress while peer-to-peer tenant access remains restricted. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
B:High-priority services meet policy while excess traffic is bounded and ordinary customer classes retain their contracted forwarding share. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
D:Only authorized customer VPNs extend between providers and payload forwarding follows a valid label-switched or agreed interconnect path. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
Question 500
For an original SPCOR service-provider engineering scenario, consider: A customer's multicast video stream crosses an MPLS VPN but the provider builds only unicast VRF routes and expects replication to happen automatically. Select THREE compatible elements: a proper correction, a targeted diagnostic and an acceptance result.
- Result: The ring remains loop-free at steady state and service recovers through the allowed protection topology with traceable alarms.
- Change: Define separate VRFs with correct route distinguishers and coordinated route-target import and export policies and confirm PE-to-PE labeled reachability.
- Change: Configure the supported mVPN multicast control-plane and provider transport distribution according to receiver membership and traffic scale.
- Check: Inspect customer PIM state, mVPN BGP or tree signaling, receiver joins, replication counters and stream reachability between PEs.
- Check: Check class-map matches, DSCP or MPLS TC, policer violations, shaping queue depth, WRED counters and customer throughput during controlled congestion.
- Result: Only authorized receiving VPN sites get the multicast data and replication uses the intended provider transport resources.
Explanation
Correct Answer
C:Acceptance: Only authorized receiving VPN sites get the multicast data and replication uses the intended provider transport resources. Applied case: A customer's multicast video stream crosses an MPLS VPN but the provider builds only unicast VRF routes and expects replication to happen automatically.
D:Acceptance: Only authorized receiving VPN sites get the multicast data and replication uses the intended provider transport resources. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
F:MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange. Required intervention: Configure the supported mVPN multicast control-plane and provider transport distribution according to receiver membership and traffic scale.
Incorrect Answers
A:Result: The ring remains loop-free at steady state and service recovers through the allowed protection topology with traceable alarms. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
B:Change: Define separate VRFs with correct route distinguishers and coordinated route-target import and export policies and confirm PE-to-PE labeled reachability. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
E:Check: Check class-map matches, DSCP or MPLS TC, policer violations, shaping queue depth, WRED counters and customer throughput during controlled congestion. MVPN extends multicast services through customer VPN contexts, using signaling and core replication trees distinct from ordinary unicast VPN route exchange.
