Cisco 350-501 Practice Test 49
Question 480
For an original SPCOR service-provider engineering scenario, consider: Two carriers agree to exchange customer VPN routes but advertise them over ordinary IPv4 unicast with no route-target or label context across the inter-AS boundary. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Exchange unqualified internet routes between carriers and assume all customers now have isolated inter-AS MPLS VPN service.
- Check: Capture ingress and egress Ethernet frames including TPID, tag stack and VLAN IDs for two isolated customers.
- Check: Trace VPNv4 advertisements, ASBR or RR roles, per-hop label stack and route-target import on a two-AS test topology.
- Change: Match ingress encapsulation, symmetric tag rewrite and EVC service instances to the contracted UNI format end to end.
- Change: 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
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. Acceptance: Only authorized customer VPNs extend between providers and payload forwarding follows a valid label-switched or agreed interconnect path.
E: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. Evidence: Trace VPNv4 advertisements, ASBR or RR roles, per-hop label stack and route-target import on a two-AS test topology.
Incorrect Answers
A:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. 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.
B:Check: Capture ingress and egress Ethernet frames including TPID, tag stack and VLAN IDs for two isolated customers. 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.
D:Change: Match ingress encapsulation, symmetric tag rewrite and EVC service instances to the contracted UNI format end to end. 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.
Question 481
A service provider network engineer is reviewing this backbone or customer-service scenario: A PE in one AS receives remote VPNv4 NLRI but its BGP next hop lacks a valid transport or service label and traffic fails. A proposed shortcut is: Exchange unqualified internet routes between carriers and assume all customers now have isolated inter-AS MPLS VPN service. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Use matching IGMP or MLD listener protocols and supported source-filtering behavior on the appropriate IPv4 or IPv6 access segment.
- Exchange unqualified internet routes between carriers and assume all customers now have isolated inter-AS MPLS VPN service.
- 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
D:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A PE in one AS receives remote VPNv4 NLRI but its BGP next hop lacks a valid transport or service label and traffic fails.
Incorrect Answers
A:Use matching IGMP or MLD listener protocols and supported source-filtering behavior on the appropriate IPv4 or IPv6 access segment. 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.
B: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. Applied case: A PE in one AS receives remote VPNv4 NLRI but its BGP next hop lacks a valid transport or service label and traffic fails.
C:Configure consistent service and customer VLAN tag handling with explicit encapsulation and correct cross-PE mapping. 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.
Question 482
A Cisco service provider design review finds: A PE in one AS receives remote VPNv4 NLRI but its BGP next hop lacks a valid transport or service label and traffic fails. The team proposes: Select the supported Inter-AS VPN option and validate labeled VPN route exchange, route targets and transport next-hop resolution at each boundary. 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.
- Policing can drop or remark out-of-profile traffic, shaping buffers and paces egress, and weighted congestion avoidance can reduce tail-drop pressure under load.
- EVPN multihoming coordinates PE participation through Ethernet segment routes and forwarder election to prevent loops and maintain reachability.
- 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.
Explanation
Correct Answer
D:Demonstrable success requires: Only authorized customer VPNs extend between providers and payload forwarding follows a valid label-switched or agreed interconnect path. Applied case: A PE in one AS receives remote VPNv4 NLRI but its BGP next hop lacks a valid transport or service label and traffic fails.
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 PE in one AS receives remote VPNv4 NLRI but its BGP next hop lacks a valid transport or service label and traffic fails.
B:Policing can drop or remark out-of-profile traffic, shaping buffers and paces egress, and weighted congestion avoidance can reduce tail-drop pressure under load. 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.
C:EVPN multihoming coordinates PE participation through Ethernet segment routes and forwarder election to prevent loops and maintain reachability. 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.
Question 483
The service provider operations team has not yet approved a change. Current evidence indicates: A PE in one AS receives remote VPNv4 NLRI but its BGP next hop lacks a valid transport or service label and traffic fails. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Inspect customer PIM state, mVPN BGP or tree signaling, receiver joins, replication counters and stream reachability between PEs.
- Trace VPNv4 advertisements, ASBR or RR roles, per-hop label stack and route-target import on a two-AS test topology.
- Compare imported RT lists, VRF next hops, shared service return routing and firewall policy using two customer tenants.
- Capture tagged or untagged frames at both UNIs, check service instance counters and confirm expected VLAN identity after a full round trip.
Explanation
Correct Answer
B: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. Confirm afterward that: Only authorized customer VPNs extend between providers and payload forwarding follows a valid label-switched or agreed interconnect path.
Incorrect Answers
A:Inspect customer PIM state, mVPN BGP or tree signaling, receiver joins, replication counters and stream reachability between PEs. 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.
C:Compare imported RT lists, VRF next hops, shared service return routing and firewall policy using two customer tenants. 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.
D:Capture tagged or untagged frames at both UNIs, check service instance counters and confirm expected VLAN identity after a full round trip. 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.
Question 484
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A PE in one AS receives remote VPNv4 NLRI but its BGP next hop lacks a valid transport or service label and traffic fails. 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.
- Customer devices receive frames in the specified tagging format and service VLANs remain separated despite provider translations.
- Each customer's original VLAN identity is preserved or intentionally translated and service isolation remains intact across the provider.
- The ring remains loop-free at steady state and service recovers through the allowed protection topology with traceable alarms.
- Only authorized customer VPNs extend between providers and payload forwarding follows a valid label-switched or agreed interconnect path.
Explanation
Correct Answer
D: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. The approved implementation step was: Select the supported Inter-AS VPN option and validate labeled VPN route exchange, route targets and transport next-hop resolution at each boundary.
Incorrect Answers
A:Customer devices receive frames in the specified tagging format and service VLANs remain separated despite provider translations. 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.
B:Each customer's original VLAN identity is preserved or intentionally translated and service isolation remains intact across the provider. 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.
C:This option addresses a different service provider engineering topic (G.8032 ring and Ethernet OAM fault isolation) rather than the documented Inter-AS MPLS L3VPN route exchange and labels decision.
Question 485
An implementation sign-off request identifies the following problem: A PE in one AS receives remote VPNv4 NLRI but its BGP next hop lacks a valid transport or service label and traffic fails. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- Change: Match ingress encapsulation, symmetric tag rewrite and EVC service instances to the contracted UNI format end to end. Verify: Capture tagged or untagged frames at both UNIs, check service instance counters and confirm expected VLAN identity after a full round trip.
- Change: Match multicast routing mode and receiver source selection, then verify PIM RPF and RP or source-tree behavior for the chosen model. Verify: Inspect (*,G) and (S,G) state, RP mapping, RPF interface and actual receiver joins under a test stream.
- Change: Build selective route leaking or shared-service VRF connectivity with scoped route targets and explicit security controls for shared and internet paths. Verify: Compare imported RT lists, VRF next hops, shared service return routing and firewall policy using two customer tenants.
- 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
D: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. The change is successful only when: Only authorized customer VPNs extend between providers and payload forwarding follows a valid label-switched or agreed interconnect path.
Incorrect Answers
A:Change: Match ingress encapsulation, symmetric tag rewrite and EVC service instances to the contracted UNI format end to end. A PE in one AS receives remote VPNv4 NLRI but its BGP next hop lacks a valid transport or service label and traffic fails.
B:Change: Match multicast routing mode and receiver source selection, then verify PIM RPF and RP or source-tree behavior for the chosen model.
C:Change: Build selective route leaking or shared-service VRF connectivity with scoped route targets and explicit security controls for shared and internet paths. 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.
Question 486
A service provider network engineer is reviewing this backbone or customer-service scenario: 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. 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.
- Build the supported carrier-supporting-carrier transport and routing boundary, retaining customer-carrier control where intended and validating labeled reachability.
- Build selective route leaking or shared-service VRF connectivity with scoped route targets and explicit security controls for shared and internet paths.
- Flood the downstream carrier's complete customer service table into every provider core router as an obligatory transit step.
- Configure consistent service and customer VLAN tag handling with explicit encapsulation and correct cross-PE mapping.
Explanation
Correct Answer
A:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: 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.
Incorrect Answers
B:Build selective route leaking or shared-service VRF connectivity with scoped route targets and explicit security controls for shared and internet paths. 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:Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
D: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.
Question 487
A Cisco service provider design review finds: 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. 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.
- Carrier supporting carrier lets a provider transport another carrier's VPN or MPLS reachability without needing full visibility into every downstream end-customer route.
- IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
- IEEE 802.1ad provider bridging adds a service tag outside customer VLAN tags, and tag roles must remain consistent through the carrier network.
- A route distinguisher makes overlapping VPN routes uniquely identifiable, whereas route targets control membership and distribution of VPN routing information.
Explanation
Correct Answer
A:Demonstrable success requires: The customer carrier preserves its own service topology while the backbone transports authorized labeled traffic without core route explosion. This principle explains the proposed technical approach, which is: Build the supported carrier-supporting-carrier transport and routing boundary, retaining customer-carrier control where intended and validating labeled reachability.
Incorrect Answers
B:IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support. 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: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.
D:A route distinguisher makes overlapping VPN routes uniquely identifiable, whereas route targets control membership and distribution of VPN routing information. 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 488
The service provider operations team has not yet approved a change. Current evidence indicates: 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. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Inspect customer PIM state, mVPN BGP or tree signaling, receiver joins, replication counters and stream reachability between PEs.
- Capture ingress and egress Ethernet frames including TPID, tag stack and VLAN IDs for two isolated customers.
- Check labeled route handoff, VRF or transport separation, next-hop reachability and a representative downstream customer LSP.
- Capture tagged or untagged frames at both UNIs, check service instance counters and confirm expected VLAN identity after a full round trip.
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. Applied case: 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.
Incorrect Answers
A:This option addresses a different service provider engineering topic (Multicast VPN mVPN inclusive and selective trees) rather than the documented Carrier supporting carrier hierarchical VPN transport decision.
B:Capture ingress and egress Ethernet frames including TPID, tag stack and VLAN IDs for two isolated customers. 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 (EVC VLAN push pop rewrite and service delimiting) rather than the documented Carrier supporting carrier hierarchical VPN transport decision.
Question 489
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: 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. 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.
- The customer carrier preserves its own service topology while the backbone transports authorized labeled traffic without core route explosion.
- Permitted locations communicate according to the contracted Ethernet service while disallowed leaf or tenant pairs remain isolated.
- Customer MACs or prefixes resolve to the appropriate remote PE without leaking between unrelated EVPN instances.
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 approved implementation step was: Build the supported carrier-supporting-carrier transport and routing boundary, retaining customer-carrier control where intended and validating labeled reachability.
Incorrect Answers
A:Customers reach only approved shared services and internet egress while peer-to-peer tenant access remains restricted. 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: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:Customer MACs or prefixes resolve to the appropriate remote PE without leaking between unrelated EVPN instances. 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 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.
