Cisco 350-501 Practice Test 58
Question 570
For an original SPCOR service-provider engineering scenario, consider: A multicast source sends to a sparse-mode group but receivers receive no packets because the designated RP address is unreachable from the first-hop router. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Configure an RP-dependent workflow for SSM and assume group-only subscriptions identify any required source automatically.
- Check: Inspect (*,G) and (S,G) state, RP mapping, RPF interface and actual receiver joins under a test stream.
- Change: Use matching IGMP or MLD listener protocols and supported source-filtering behavior on the appropriate IPv4 or IPv6 access segment.
- Change: Match multicast routing mode and receiver source selection, then verify PIM RPF and RP or source-tree behavior for the chosen model.
- Check: Inspect customer PIM state, mVPN BGP or tree signaling, receiver joins, replication counters and stream reachability between PEs.
Explanation
Correct Answer
B:PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery. Acceptance: Intended subscribers receive the selected source and nonmembers do not trigger unwanted flood or RP dependence.
D:PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery. Evidence: Inspect (*,G) and (S,G) state, RP mapping, RPF interface and actual receiver joins under a test stream.
Incorrect Answers
A:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
C:Change: Use matching IGMP or MLD listener protocols and supported source-filtering behavior on the appropriate IPv4 or IPv6 access segment. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
E:Check: Inspect customer PIM state, mVPN BGP or tree signaling, receiver joins, replication counters and stream reachability between PEs. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
Question 571
A service provider network engineer is reviewing this backbone or customer-service scenario: A network uses PIM-SSM with group-specific source subscription yet the receiver performs only a wildcard group join and expects source-specific forwarding. A proposed shortcut is: Configure an RP-dependent workflow for SSM and assume group-only subscriptions identify any required source automatically. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Match multicast routing mode and receiver source selection, then verify PIM RPF and RP or source-tree behavior for the chosen model.
- Configure a consistent Ethernet Segment Identifier and supported designated-forwarder or split-horizon behavior for the multihoming model.
- Match the Ethernet service type to required point-to-point, multipoint or rooted traffic relationships and enforce the appropriate endpoint split rules.
- Configure an RP-dependent workflow for SSM and assume group-only subscriptions identify any required source automatically.
Explanation
Correct Answer
A:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A network uses PIM-SSM with group-specific source subscription yet the receiver performs only a wildcard group join and expects source-specific forwarding.
Incorrect Answers
B:Configure a consistent Ethernet Segment Identifier and supported designated-forwarder or split-horizon behavior for the multihoming model. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
C:Match the Ethernet service type to required point-to-point, multipoint or rooted traffic relationships and enforce the appropriate endpoint split rules. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
D:PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery. Applied case: A network uses PIM-SSM with group-specific source subscription yet the receiver performs only a wildcard group join and expects source-specific forwarding.
Question 572
A Cisco service provider design review finds: A network uses PIM-SSM with group-specific source subscription yet the receiver performs only a wildcard group join and expects source-specific forwarding. The team proposes: Match multicast routing mode and receiver source selection, then verify PIM RPF and RP or source-tree behavior for the chosen model. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- L3VPN extranet services require controlled cross-VRF routing and return reachability; sharing a few service routes need not grant full tenant-to-tenant visibility.
- PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
- 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.
- EVC tag operations such as push pop and translation are contextual to a service instance and may require symmetric rewrite at both attachment points.
Explanation
Correct Answer
B:Demonstrable success requires: Intended subscribers receive the selected source and nonmembers do not trigger unwanted flood or RP dependence. Applied case: A network uses PIM-SSM with group-specific source subscription yet the receiver performs only a wildcard group join and expects source-specific forwarding.
Incorrect Answers
A:L3VPN extranet services require controlled cross-VRF routing and return reachability; sharing a few service routes need not grant full tenant-to-tenant visibility. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
C: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. A network uses PIM-SSM with group-specific source subscription yet the receiver performs only a wildcard group join and expects source-specific forwarding.
D:EVC tag operations such as push pop and translation are contextual to a service instance and may require symmetric rewrite at both attachment points. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
Question 573
The service provider operations team has not yet approved a change. Current evidence indicates: A network uses PIM-SSM with group-specific source subscription yet the receiver performs only a wildcard group join and expects source-specific forwarding. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Trace VPNv4 advertisements, ASBR or RR roles, per-hop label stack and route-target import on a two-AS test topology.
- Check class-map matches, DSCP or MPLS TC, policer violations, shaping queue depth, WRED counters and customer throughput during controlled congestion.
- Capture tagged or untagged frames at both UNIs, check service instance counters and confirm expected VLAN identity after a full round trip.
- Inspect (*,G) and (S,G) state, RP mapping, RPF interface and actual receiver joins under a test stream.
Explanation
Correct Answer
D:PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery. Confirm afterward that: Intended subscribers receive the selected source and nonmembers do not trigger unwanted flood or RP dependence.
Incorrect Answers
A:Trace VPNv4 advertisements, ASBR or RR roles, per-hop label stack and route-target import on a two-AS test topology. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
B:Check class-map matches, DSCP or MPLS TC, policer violations, shaping queue depth, WRED counters and customer throughput during controlled congestion. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
C:Capture tagged or untagged frames at both UNIs, check service instance counters and confirm expected VLAN identity after a full round trip. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
Question 574
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A network uses PIM-SSM with group-specific source subscription yet the receiver performs only a wildcard group join and expects source-specific forwarding. 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.
- Customers reach only approved shared services and internet egress while peer-to-peer tenant access remains restricted.
- Intended subscribers receive the selected source and nonmembers do not trigger unwanted flood or RP dependence.
- Subscribers receive only authorized group and source traffic with no unnecessary replication to idle access ports.
Explanation
Correct Answer
C:PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery. The approved implementation step was: Match multicast routing mode and receiver source selection, then verify PIM RPF and RP or source-tree behavior for the chosen model.
Incorrect Answers
A:Customer devices receive frames in the specified tagging format and service VLANs remain separated despite provider translations. A network uses PIM-SSM with group-specific source subscription yet the receiver performs only a wildcard group join and expects source-specific forwarding.
B:Customers reach only approved shared services and internet egress while peer-to-peer tenant access remains restricted. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
D:Subscribers receive only authorized group and source traffic with no unnecessary replication to idle access ports. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
Question 575
An implementation sign-off request identifies the following problem: A network uses PIM-SSM with group-specific source subscription yet the receiver performs only a wildcard group join and expects source-specific forwarding. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- Change: Define separate VRFs with correct route distinguishers and coordinated route-target import and export policies and confirm PE-to-PE labeled reachability. Verify: Examine VRF route tables, RD, RT extended communities, MP-BGP updates and the transport plus VPN label stack.
- Change: Configure a consistent Ethernet Segment Identifier and supported designated-forwarder or split-horizon behavior for the multihoming model. Verify: Compare ESI advertisements, DF election, MAC mobility sequence and traffic behavior before and after one PE uplink failure.
- 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.
- 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.
Explanation
Correct Answer
D:PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery. The change is successful only when: Intended subscribers receive the selected source and nonmembers do not trigger unwanted flood or RP dependence.
Incorrect Answers
A:This option addresses a different service provider engineering topic (MPLS L3VPN RD RT and VRF import export) rather than the documented PIM sparse-mode SSM and rendezvous-point behavior decision.
B:Change: Configure a consistent Ethernet Segment Identifier and supported designated-forwarder or split-horizon behavior for the multihoming model. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
C:Change: Select the supported Inter-AS VPN option and validate labeled VPN route exchange, route targets and transport next-hop resolution at each boundary. PIM-SM may use a rendezvous point for shared-tree discovery, while SSM uses explicit source-group state and normally avoids RP discovery.
Question 576
A service provider network engineer is reviewing this backbone or customer-service scenario: A provider carries IPv6 multicast but watches only IGMP group counters and concludes that no receivers exist in the IPv6 subnet. A proposed shortcut is: Treat IPv6 MLD as interchangeable with IPv4-only IGMP and ignore source-filtering information in SSM services. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Select the supported Inter-AS VPN option and validate labeled VPN route exchange, route targets and transport next-hop resolution at each boundary.
- Use matching IGMP or MLD listener protocols and supported source-filtering behavior on the appropriate IPv4 or IPv6 access segment.
- Enable supported ring protection and Ethernet OAM mechanisms to enforce a loop-free normal state and verify service continuity after failure.
- Treat IPv6 MLD as interchangeable with IPv4-only IGMP and ignore source-filtering information in SSM services.
Explanation
Correct Answer
B:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A provider carries IPv6 multicast but watches only IGMP group counters and concludes that no receivers exist in the IPv6 subnet.
Incorrect Answers
A:Select the supported Inter-AS VPN option and validate labeled VPN route exchange, route targets and transport next-hop resolution at each boundary. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
C:Enable supported ring protection and Ethernet OAM mechanisms to enforce a loop-free normal state and verify service continuity after failure. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
D:IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
Question 577
A Cisco service provider design review finds: A provider carries IPv6 multicast but watches only IGMP group counters and concludes that no receivers exist in the IPv6 subnet. The team proposes: Use matching IGMP or MLD listener protocols and supported source-filtering behavior on the appropriate IPv4 or IPv6 access segment. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- EVC tag operations such as push pop and translation are contextual to a service instance and may require symmetric rewrite at both attachment points.
- EVPN multihoming coordinates PE participation through Ethernet segment routes and forwarder election to prevent loops and maintain reachability.
- IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
- E-Line is point-to-point, E-LAN is multipoint and E-Tree distinguishes root and leaf connectivity, requiring deliberate forwarding restrictions.
Explanation
Correct Answer
C:Demonstrable success requires: Subscribers receive only authorized group and source traffic with no unnecessary replication to idle access ports. Applied case: A provider carries IPv6 multicast but watches only IGMP group counters and concludes that no receivers exist in the IPv6 subnet.
Incorrect Answers
A:EVC tag operations such as push pop and translation are contextual to a service instance and may require symmetric rewrite at both attachment points. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
B:EVPN multihoming coordinates PE participation through Ethernet segment routes and forwarder election to prevent loops and maintain reachability. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
D:E-Line is point-to-point, E-LAN is multipoint and E-Tree distinguishes root and leaf connectivity, requiring deliberate forwarding restrictions. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
Question 578
The service provider operations team has not yet approved a change. Current evidence indicates: A provider carries IPv6 multicast but watches only IGMP group counters and concludes that no receivers exist in the IPv6 subnet. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Inspect IGMPv3 source lists or MLD reports, snooping table, receiver membership and forwarded multicast stream source identities.
- 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.
- 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:IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support. Applied case: A provider carries IPv6 multicast but watches only IGMP group counters and concludes that no receivers exist in the IPv6 subnet.
Incorrect Answers
B:Check labeled route handoff, VRF or transport separation, next-hop reachability and a representative downstream customer LSP. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
C:Inspect ring protection state, OAM continuity-check results, link-failure events and convergence on one forced-ring break. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
D:Trace VPNv4 advertisements, ASBR or RR roles, per-hop label stack and route-target import on a two-AS test topology. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
Question 579
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A provider carries IPv6 multicast but watches only IGMP group counters and concludes that no receivers exist in the IPv6 subnet. 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.
- High-priority services meet policy while excess traffic is bounded and ordinary customer classes retain their contracted forwarding share.
- The customer carrier preserves its own service topology while the backbone transports authorized labeled traffic without core route explosion.
- The dual-homed customer retains connectivity with correct single-copy flooding and no persistent Layer-2 forwarding loops.
- Subscribers receive only authorized group and source traffic with no unnecessary replication to idle access ports.
Explanation
Correct Answer
D:IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support. The result must be validated using the documented device, service or access context.
Incorrect Answers
A:This option addresses a different service provider engineering topic (QoS classification marking policing shaping and WRED) rather than the documented IGMPv3 MLD and multicast membership scope decision.
B:The customer carrier preserves its own service topology while the backbone transports authorized labeled traffic without core route explosion. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
C:The dual-homed customer retains connectivity with correct single-copy flooding and no persistent Layer-2 forwarding loops. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
Question 580
For an original SPCOR service-provider engineering scenario, consider: A provider carries IPv6 multicast but watches only IGMP group counters and concludes that no receivers exist in the IPv6 subnet. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Check: Check EVPN address-family advertisements, route types, Ethernet segment and EVI context, route targets and remote forwarding database.
- Treat IPv6 MLD as interchangeable with IPv4-only IGMP and ignore source-filtering information in SSM services.
- Change: Build selective route leaking or shared-service VRF connectivity with scoped route targets and explicit security controls for shared and internet paths.
- Change: Use matching IGMP or MLD listener protocols and supported source-filtering behavior on the appropriate IPv4 or IPv6 access segment.
- Check: Inspect IGMPv3 source lists or MLD reports, snooping table, receiver membership and forwarded multicast stream source identities.
Explanation
Correct Answer
D:IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support. Acceptance: Subscribers receive only authorized group and source traffic with no unnecessary replication to idle access ports.
E:IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support. Required intervention: Use matching IGMP or MLD listener protocols and supported source-filtering behavior on the appropriate IPv4 or IPv6 access segment.
Incorrect Answers
A:Check: Check EVPN address-family advertisements, route types, Ethernet segment and EVI context, route targets and remote forwarding database. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
B:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. IGMP manages IPv4 multicast listener memberships, MLD handles IPv6, and source-specific filtering depends on listener protocol and switch or router support.
C:This option addresses a different service provider engineering topic (L3VPN extranet shared service and internet breakout) rather than the documented IGMPv3 MLD and multicast membership scope decision.
