Cisco CCNP Enterprise 350-401 ENCOR Multicast Forwarding and Distribution Models Practice Test

 

Topic 11 covers multicast forwarding and distribution models for the Cisco Certified Specialist – Enterprise Core certification. These original practice questions apply the verified 350-401 objectives to practical decisions and troubleshooting. Select one answer unless a fixed number is requested. For broader preparation, visit the Cisco 350-401 ENCOR Exam Dumps page. Each option includes an explanation of the relevant behavior and scenario constraints.

Question 1

R1 receives multicast packets from source 10.10.10.10 on Gi0/2. The unicast routing table says the best route back to 10.10.10.10 is through Gi0/1. What does the RPF check normally conclude?

1. The packets pass if at least one receiver joined the group.
2. The router changes the unicast route to Gi0/2 automatically.
3. The packets pass because Gi0/2 is physically up.
4. The packets fail RPF because they arrived on the wrong interface.
5. The packets pass if the destination group is in 239.0.0.0/8.

Correct Answer: D

 

Correct Answer

Answer D is correct because RPF uses the unicast route toward the source to determine the expected incoming interface.

Incorrect Answers

Answer A is incorrect because receiver membership and source-side RPF are separate conditions.

Answer B is incorrect because receiving multicast traffic does not rewrite the unicast RIB to satisfy RPF.

Answer C is incorrect because physical state alone does not satisfy the reverse-path check.

Answer E is incorrect because group range does not override the stated wrong incoming interface.

 

Question 2

A multicast source is reachable by unicast through Gi0/0. The multicast stream instead arrives on Gi0/3 because of an asymmetric upstream design. Receivers are joined correctly, but R1 discards the stream. What is the most direct explanation?

1. PIM sparse mode requires every source to use the receiver-facing interface.
2. IGMP membership forces all traffic to use Gi0/3.
3. The group must be converted to broadcast.
4. The stream arrived on the non-RPF interface.
5. The router needs a lower HSRP priority.

Correct Answer: D

 

Correct Answer

Answer D is correct because the asymmetric multicast path conflicts with the unicast route used for the reverse-path decision.

Incorrect Answers

Answer A is incorrect because PIM does not require source traffic to enter on a receiver interface.

Answer B is incorrect because IGMP records receiver interest; it does not override source RPF.

Answer C is incorrect because broadcast conversion is not the remedy for an RPF failure.

Answer E is incorrect because FHRP priority is unrelated to multicast RPF. It does not satisfy the stem’s governing point: Asymmetric multicast forwarding can fail when the incoming interface does not match the unicast reverse path to the source.

 

Question 3

R1 has a valid unicast route to multicast source 192.0.2.10 and therefore knows the RPF interface. No hosts on R1 downstream LANs have joined group 239.1.1.1, and no downstream PIM joins exist. Which statement is correct?

1. RPF reachability alone does not create receiver interest.
2. The route to the source proves an IGMP join exists.
3. A valid source route automatically makes every interface an outgoing multicast interface.
4. The router must flood the multicast to all LANs.
5. The source route is ignored because multicast never uses unicast information.

Correct Answer: A

 

Correct Answer

Answer A is correct because RPF validates incoming direction; receiver membership/join state drives where multicast should be replicated.

Incorrect Answers

Answer B is incorrect because unicast routing and IGMP host membership are separate state.

Answer C is incorrect because multicast forwarding is receiver-driven in sparse designs. It does not satisfy the stem’s governing point: Keep source-side RPF state separate from receiver membership and outgoing multicast forwarding state.

Answer D is incorrect because PIM sparse mode does not flood traffic without explicit interest.

Answer E is incorrect because RPF explicitly uses routing information toward the source.

 

Question 4

The unicast IGP prefers a path to source S through Core-A, but multicast traffic from S is intentionally engineered to enter through Core-B with no corresponding RPF override or routing change. What risk exists?

1. MSDP forwards the packet around RPF.
2. PIM automatically changes the IGP route to Core-B.
3. The engineered path can fail RPF because the reverse route still uses Core-A.
4. Bidir PIM makes all incoming interfaces valid for every source.
5. IGMPv3 EXCLUDE mode disables RPF.

Correct Answer: C

 

Correct Answer

Answer C is correct because multicast path engineering must remain consistent with the RPF decision or provide supported RPF mechanisms.

Incorrect Answers

Answer A is incorrect because MSDP distributes source information, not user packets that bypass RPF.

Answer B is incorrect because PIM does not normally rewrite unicast routing merely to accommodate the stream.

Answer D is incorrect because bidirectional operation does not mean arbitrary source-interface checks vanish without proper forwarding state.

Answer E is incorrect because IGMP source filtering does not turn off router RPF checks.

 

Question 5

A multicast route entry has incoming interface Gi0/1 and outgoing interface list Gi0/2, Gi0/3, and Gi0/4. One packet from the source arrives correctly on Gi0/1. What does normal multicast forwarding do with that packet?

1. Wait for HSRP election before forwarding.
2. Send the packet back out Gi0/1 as well.
3. Replicate the packet to the eligible outgoing interfaces.
4. Convert it to three unicast TCP sessions.
5. Choose only the numerically lowest outgoing interface.

Correct Answer: C

 

Correct Answer

Answer C is correct because multicast routers can copy one incoming packet to multiple downstream interfaces with receiver/join state.

Incorrect Answers

Answer A is incorrect because first-hop gateway election is unrelated to the supplied multicast route state.

Answer B is incorrect because the incoming RPF interface is not normally an outgoing replication branch for the same entry.

Answer D is incorrect because multicast forwarding replicates multicast packets rather than creating TCP connections.

Answer E is incorrect because multicast replication is not a single-next-hop unicast decision when multiple downstream branches need the stream.

 

Question 6

In a PIM sparse-mode any-source multicast deployment, what is the key function of the rendezvous point during shared-tree operation?

1. Assign DHCP addresses to multicast receivers.
2. Translate multicast groups to public IPv4 addresses.
3. Provide the shared-tree meeting point for sources and receivers.
4. Serve as the Layer 2 STP root.
5. Store every user packet permanently.

Correct Answer: C

 

Correct Answer

Answer C is correct because the RP connects source and receiver discovery/control for PIM-SM shared-tree operation.

Incorrect Answers

Answer A is incorrect because address assignment is not the RP role. It does not satisfy the stem’s governing point: PIM-SM uses an RP as the shared-tree rendezvous/control point for sources and receivers.

Answer B is incorrect because NAT is not the RP function. It does not satisfy the stem’s governing point: PIM-SM uses an RP as the shared-tree rendezvous/control point for sources and receivers.

Answer D is incorrect because spanning-tree election is unrelated to PIM-SM RP behavior.

Answer E is incorrect because the RP participates in multicast control/forwarding, not archival storage.

 

Question 7

A receiver first joins an RP-centered shared tree for group G, then the last-hop router later builds a shortest-path tree directly toward active source S. Which state transition is being described?

1. A VRRP master failover.
2. An MSDP TCP reset.
3. A change from IPv4 to IPv6.
4. A conversion from IGMP to NTP.
5. Move from shared-tree (*,G) to source-specific (S,G) forwarding.

Correct Answer: E

 

Correct Answer

Answer E is correct because the shared tree is group-oriented via the RP; source-tree state identifies a particular source and group.

Incorrect Answers

Answer A is incorrect because FHRP state is unrelated to multicast tree selection.

Answer B is incorrect because MSDP peer transport is not the described receiver-tree transition.

Answer C is incorrect because tree type does not imply a change of IP version.

Answer D is incorrect because receiver signaling and time synchronization are unrelated. It does not satisfy the stem’s governing point: Distinguish RP-centered shared-tree state from source-specific shortest-path state.

 

Question 8

A new multicast source starts sending in a PIM-SM domain. Its first-hop router knows the RP for the group. What high-level control behavior allows the RP to learn about that source?

1. The first-hop router can register source traffic toward the RP.
2. The receiver sends an HSRP hello to the source.
3. The source runs IGMP queries toward the RP.
4. The source must open an MSDP session directly to every receiver.
5. The RP learns only from BGP AS paths.

Correct Answer: A

 

Correct Answer

Answer A is correct because PIM-SM uses source registration so the RP becomes aware of active sources for relevant groups.

Incorrect Answers

Answer B is incorrect because HSRP is unrelated to source discovery. It does not satisfy the stem’s governing point: PIM-SM first-hop routers register active sources toward the RP at a conceptual level.

Answer C is incorrect because IGMP is primarily host-to-local-router membership signaling, not source registration to the RP.

Answer D is incorrect because MSDP peers RPs/domains and does not require sources to peer with receivers.

Answer E is incorrect because ordinary PIM-SM source registration does not depend on BGP advertisement of the multicast source.

 

Question 9

No receiver exists for group 239.10.10.10 on a downstream branch. A router on that branch has PIM sparse mode enabled but has received no Join for the group. Which forwarding behavior is expected?

1. The router floods every multicast group to all PIM interfaces.
2. Do not forward down the branch without explicit receiver interest.
3. The router sends the stream until an IGMP Leave arrives even though no join occurred.
4. The router translates the group to broadcast.
5. The router chooses an HSRP active interface for the group.

Correct Answer: B

 

Correct Answer

Answer B is correct because PIM-SM uses a receiver-driven pull model and requires explicit interest.

Incorrect Answers

Answer A is incorrect because that behavior contradicts sparse-mode receiver-driven forwarding. It does not satisfy the stem’s governing point: PIM sparse mode forwards toward branches that explicitly request the group rather than flooding everywhere.

Answer C is incorrect because without receiver/join state there is no reason to create the downstream branch.

Answer D is incorrect because PIM-SM does not automatically convert multicast into broadcast.

Answer E is incorrect because HSRP is unrelated to PIM downstream interest. It does not satisfy the stem’s governing point: PIM sparse mode forwards toward branches that explicitly request the group rather than flooding everywhere.

 

Question 10

Receivers have valid joins toward the RP, but routers cannot route to the configured RP address. Source routes are otherwise reachable. Why can ASM group establishment still fail?

1. The RP address is only decorative and need not be routed.
2. Source reachability automatically replaces RP reachability for all ASM control.
3. The RP must be reachable for ASM shared-tree control.
4. MSDP supplies a unicast route to the RP automatically.
5. IGMPv2 hosts route directly to the RP themselves.

Correct Answer: C

 

Correct Answer

Answer C is correct because PIM-SM ASM operation requires the RP control point to be reachable by the participating routers.

Incorrect Answers

Answer A is incorrect because the RP must be reachable for the control-plane exchanges that use it.

Answer B is incorrect because the source route and RP route are separate dependencies.

Answer D is incorrect because MSDP does not replace basic IP reachability to peer/RP addresses.

Answer E is incorrect because hosts signal local membership; routers build the multicast control path.

 

Question 11

A host on a LAN uses IGMPv2 to join group 239.20.20.20. What receiver intent does that signal at a high level?

1. A request to become the PIM RP.
2. The host requests group membership without IGMPv3 source filtering.
3. Interest only in source 192.0.2.1.
4. A request to create an HSRP virtual IP.
5. A request to advertise the group in BGP.

Correct Answer: B

 

Correct Answer

Answer B is correct because IGMPv2 primarily signals group membership rather than the source-filter expressions introduced by IGMPv3.

Incorrect Answers

Answer A is incorrect because host membership does not assign router RP role.

Answer C is incorrect because that source-specific intent requires source filtering behavior not expressed by a basic IGMPv2 group join.

Answer D is incorrect because FHRP is unrelated to multicast membership. It does not satisfy the stem’s governing point: IGMPv2 signals group membership but does not provide the same source-filter semantics as IGMPv3.

Answer E is incorrect because IGMP does not advertise prefixes to BGP. It does not satisfy the stem’s governing point: IGMPv2 signals group membership but does not provide the same source-filter semantics as IGMPv3.

 

Question 12

An IGMPv3 report is in INCLUDE mode for group 232.10.10.10 with sources 192.0.2.10 and 192.0.2.20. What does the host request?

1. Advertise both sources through MSDP.
2. Receive the group from every source except the listed two.
3. Become the multicast querier.
4. Receive the group from the listed sources.
5. Block the group entirely.

Correct Answer: D

 

Correct Answer

Answer D is correct because INCLUDE mode expresses interest in the specified source set for the group.

Incorrect Answers

Answer A is incorrect because host IGMP reports do not make the host an MSDP RP peer.

Answer B is incorrect because that describes EXCLUDE-style semantics. It does not satisfy the stem’s governing point: IGMPv3 INCLUDE expresses positive interest in the listed source set for a group.

Answer C is incorrect because source-filter membership does not elect the host as querier.

Answer E is incorrect because a nonempty INCLUDE list requests those source channels.

 

Question 13

An IGMPv3 report is EXCLUDE mode for group G with source set {S1,S2}. Which interpretation is closest?

1. The receiver has left group G completely.
2. Receive the group from sources other than the excluded set.
3. The receiver wants only S1 and S2.
4. The receiver is defining the RP address.
5. The router must drop all multicast from every source.

Correct Answer: B

 

Correct Answer

Answer B is correct because EXCLUDE mode identifies sources the receiver does not want while accepting other sources for the group.

Incorrect Answers

Answer A is incorrect because EXCLUDE with a source list is not equivalent to leaving the group.

Answer C is incorrect because that is INCLUDE-style intent. It does not satisfy the stem’s governing point: IGMPv3 EXCLUDE expresses group interest while excluding specified source traffic.

Answer D is incorrect because IGMP source filtering does not configure an RP.

Answer E is incorrect because the intent is selective source exclusion rather than universal group blocking.

 

Question 14

Three multicast receivers share one Ethernet LAN. Which device function maintains the local IGMP membership state by sending membership queries on that LAN?

1. The PIM RP in every case, even if it is elsewhere.
2. The NAT outside interface.
3. The BGP route reflector.
4. The LAN IGMP querier sends the membership queries.
5. The HSRP standby device only.

Correct Answer: D

 

Correct Answer

Answer D is correct because the querier periodically asks for membership so local multicast receiver state can be maintained.

Incorrect Answers

Answer A is incorrect because the RP is not necessarily the LAN IGMP querier.

Answer B is incorrect because NAT role does not perform IGMP membership queries by definition.

Answer C is incorrect because BGP is unrelated to IGMP membership maintenance. It does not satisfy the stem’s governing point: IGMP querier operation maintains receiver membership knowledge on a local subnet.

Answer E is incorrect because FHRP role is not the definition of IGMP querier.

 

Question 15

A host sends an IGMP membership report for group G. An engineer says this message will build PIM routing state across every router to the source by itself. What is the correction?

1. IGMP is the interdomain RP-to-RP source discovery protocol.
2. IGMP replaces the unicast routing table for RPF.
3. IGMP configures the NAT translation for the group.
4. IGMP is a first-hop redundancy protocol.
5. IGMP handles local host membership; PIM handles router-to-router distribution.

Correct Answer: E

 

Correct Answer

Answer E is correct because host membership and multicast routing are separate protocol roles that interact at the last hop.

Incorrect Answers

Answer A is incorrect because MSDP historically provides that source-discovery role between RPs, not IGMP.

Answer B is incorrect because RPF relies on routing information toward the source.

Answer C is incorrect because NAT is not established by IGMP reports. It does not satisfy the stem’s governing point: Separate local host membership signaling (IGMP) from router-to-router multicast routing (PIM).

Answer D is incorrect because gateway redundancy is unrelated. It does not satisfy the stem’s governing point: Separate local host membership signaling (IGMP) from router-to-router multicast routing (PIM).

 

Question 16

In Source-Specific Multicast, what uniquely identifies the receiver channel of interest?

1. The HSRP group and virtual MAC.
2. Only the receiver IP address.
3. The RP address and VLAN ID.
4. The (S,G) source-and-group pair.
5. Only the multicast group G.

Correct Answer: D

 

Correct Answer

Answer D is correct because SSM receiver interest is source-specific as well as group-specific.

Incorrect Answers

Answer A is incorrect because FHRP data does not identify multicast content channels.

Answer B is incorrect because receiver identity is not the channel key used to specify the multicast source/group.

Answer C is incorrect because SSM is designed to avoid RP-based source discovery for the channel.

Answer E is incorrect because group-only identification describes any-source membership, not the defining SSM channel.

 

Question 17

A video application already knows its sender address S and requests (S,G) using IGMPv3 INCLUDE. Why can SSM avoid the ASM rendezvous-point source-discovery dependency for that channel?

1. SSM converts the stream to unicast at every hop.
2. SSM requires the source to own the group address.
3. SSM floods traffic until the receiver finds the source.
4. SSM requires MSDP to find S.
5. The receiver names the source, enabling direct source-specific state.

Correct Answer: E

 

Correct Answer

Answer E is correct because SSM does not need to discover an unknown source through an RP for an explicitly requested channel.

Incorrect Answers

Answer A is incorrect because the forwarding remains IP multicast. It does not satisfy the stem’s governing point: SSM uses explicit source knowledge to build (S,G) state without ASM RP source discovery.

Answer B is incorrect because source/group channel identity does not make the source the owner of the multicast group address in that sense.

Answer C is incorrect because SSM is not based on dense-mode flooding. It does not satisfy the stem’s governing point: SSM uses explicit source knowledge to build (S,G) state without ASM RP source discovery.

Answer D is incorrect because SSM explicitly avoids the ASM source-discovery dependence; MSDP SA messages are not used for SSM channels.

 

Question 18

A host should receive multicast group 232.1.1.1 only from source 198.51.100.10. Which host membership behavior best matches SSM?

198. IGMPv3 INCLUDE for 198.51.100.10 with group 232.1.1.1.
199. IGMPv2 group-only join with no source information.
200. MSDP SA from the receiver.
201. IGMPv3 EXCLUDE for 198.51.100.10.
202. PIM Register from the host directly to an RP.

Correct Answer: A

 

Correct Answer

Answer A is correct because SSM uses source-specific subscription, typically expressed with IGMPv3 INCLUDE state.

Incorrect Answers

Answer B is incorrect because that cannot express the desired source-specific channel directly.

Answer C is incorrect because MSDP is not host membership signaling. It does not satisfy the stem’s governing point: SSM receiver signaling needs positive source-specific membership for the desired source/group channel.

Answer D is incorrect because that would express the opposite filtering intent. It does not satisfy the stem’s governing point: SSM receiver signaling needs positive source-specific membership for the desired source/group channel.

Answer E is incorrect because hosts do not normally use PIM Register to subscribe.

 

Question 19

A receiver sends a group-only membership report for G but does not identify source S. The application requirement is explicitly to subscribe only to S for that group. What is missing?

1. The receiver must identify source S in its membership state.
2. A BGP community on G.
3. An HSRP virtual IP for S.
4. A lower PTP clock priority.
5. A NAT static translation for the receiver.

Correct Answer: A

 

Correct Answer

Answer A is correct because the SSM application requirement is not met by group-only interest when the source must be selected.

Incorrect Answers

Answer B is incorrect because BGP route attributes do not replace host source-filter membership.

Answer C is incorrect because gateway redundancy does not express multicast source interest.

Answer D is incorrect because time synchronization is unrelated. It does not satisfy the stem’s governing point: A group-only join does not express an SSM (S,G) subscription when the source must be specified.

Answer E is incorrect because address translation is unrelated to selecting a multicast source.

 

Question 20

An SSM deployment assumes the application supplies source addresses through a directory/service. That directory fails, although the multicast network is healthy. What user impact can occur?

1. PIM automatically converts every SSM group into ASM and discovers sources through any RP.
2. Routers lose their IP addresses.
3. All multicast forwarding stops because RPF no longer uses unicast routes.
4. The group becomes an HSRP virtual router.
5. Receivers cannot form (S,G) subscriptions without knowing the source.

Correct Answer: E

 

Correct Answer

Answer E is correct because SSM shifts source discovery toward the application/service; loss of that information can prevent subscription despite healthy routing.

Incorrect Answers

Answer A is incorrect because that would change the service model and is not an automatic guarantee.

Answer B is incorrect because the source directory does not assign router addressing in this scenario.

Answer C is incorrect because RPF behavior remains; the stated problem is application source discovery.

Answer D is incorrect because FHRP is unrelated. It does not satisfy the stem’s governing point: SSM depends on the application or another mechanism knowing the desired source address.

 

Question 21

An enterprise has many multicast senders and many receivers for the same collaborative groups, and it wants to avoid building a separate source tree for every sender. Which PIM model is designed around a bidirectional shared tree for this many-to-many pattern?

1. Bidirectional PIM.
2. HSRP.
3. IGMPv2 alone.
4. PBR.
5. SSM only.

Correct Answer: A

 

Correct Answer

Answer A is correct because bidir PIM keeps traffic on a shared bidirectional tree and is suited to many-to-many source patterns.

Incorrect Answers

Answer B is incorrect because gateway redundancy is unrelated to multicast tree construction.

Answer C is incorrect because IGMP is host membership signaling and does not define inter-router tree architecture.

Answer D is incorrect because policy-based routing handles selected unicast forwarding policy rather than a multicast distribution tree.

Answer E is incorrect because SSM is source-specific and commonly fits one-to-many known-source delivery rather than a shared many-to-many tree.

 

Question 22

On a multiaccess segment in bidirectional PIM, what high-level problem does the designated forwarder mechanism address?

1. Select one router to forward between the LAN and bidirectional shared tree.
2. Choose the VRRP master gateway.
3. Select the BGP best AS path.
4. Elect the PTP grandmaster.
5. Assign NAT pool addresses.

Correct Answer: A

 

Correct Answer

Answer A is correct because a DF is selected per relevant link/RP context to provide one forwarding path on the multiaccess segment.

Incorrect Answers

Answer B is incorrect because VRRP is a separate first-hop redundancy protocol. It does not satisfy the stem’s governing point: Bidir PIM uses a designated forwarder to control forwarding on multiaccess links and avoid duplicates.

Answer C is incorrect because BGP route selection does not define bidir-PIM DF behavior.

Answer D is incorrect because PTP clock selection is unrelated. It does not satisfy the stem’s governing point: Bidir PIM uses a designated forwarder to control forwarding on multiaccess links and avoid duplicates.

Answer E is incorrect because NAT address allocation is unrelated. It does not satisfy the stem’s governing point: Bidir PIM uses a designated forwarder to control forwarding on multiaccess links and avoid duplicates.

 

Question 23

An engineer expects bidir PIM to switch each active sender onto a conventional PIM-SM source-specific shortest-path tree after a traffic threshold. What is the conceptual correction?

1. Bidir PIM disables RPF entirely.
2. Bidir PIM is only an IGMP host mode.
3. Bidir PIM can work only with a single receiver.
4. Keep forwarding on the bidirectional shared tree instead of per-source SPTs.
5. Bidir PIM requires every receiver to run BGP.

Correct Answer: D

 

Correct Answer

Answer D is correct because its scalability model avoids maintaining a separate source tree for every active sender.

Incorrect Answers

Answer A is incorrect because bidirectional forwarding still has defined control/forwarding rules; it is not arbitrary flooding.

Answer B is incorrect because it is a router multicast routing mode/model, not merely host membership signaling.

Answer C is incorrect because the model is specifically useful for shared many-to-many communication.

Answer E is incorrect because BGP is unrelated to the tree model. It does not satisfy the stem’s governing point: Do not assume PIM-SM source-tree switching behavior applies unchanged to bidirectional PIM.

 

Question 24

Two PIM-SM domains each have their own RP. A source becomes active in Domain A, and receivers in Domain B may need to learn that the source exists. What classic protocol can exchange Source-Active information between RPs?

1. MSDP.
2. IGMPv2.
3. HSRP.
4. NTP.
5. LACP.

Correct Answer: A

 

Correct Answer

Answer A is correct because MSDP peers can exchange Source-Active information so RPs in different domains learn about active ASM sources.

Incorrect Answers

Answer B is incorrect because IGMP is host-to-local-router membership signaling. It does not satisfy the stem’s governing point: MSDP provides inter-RP source discovery for ASM across PIM-SM domains.

Answer C is incorrect because HSRP is first-hop redundancy. It does not satisfy the stem’s governing point: MSDP provides inter-RP source discovery for ASM across PIM-SM domains.

Answer D is incorrect because NTP synchronizes clocks. It does not satisfy the stem’s governing point: MSDP provides inter-RP source discovery for ASM across PIM-SM domains.

Answer E is incorrect because LACP forms link aggregation groups. It does not satisfy the stem’s governing point: MSDP provides inter-RP source discovery for ASM across PIM-SM domains.

 

Question 25

An MSDP peer receives a Source-Active message about source S and group G. An engineer says MSDP will now carry the actual user multicast stream between the two domains. What is the correction?

1. MSDP eliminates the need for RPF.
2. MSDP carries source discovery; PIM carries the multicast data path.
3. MSDP turns the source into a VRRP master.
4. MSDP performs NAT on the source address.
5. MSDP replaces IP forwarding for all multicast data.

Correct Answer: B

 

Correct Answer

Answer B is correct because MSDP SA signaling tells remote RPs about sources but is not the steady-state user data transport protocol.

Incorrect Answers

Answer A is incorrect because multicast forwarding still relies on proper route/tree state.

Answer C is incorrect because FHRP roles are unrelated. It does not satisfy the stem’s governing point: Keep MSDP source discovery separate from the actual multicast user-data forwarding plane.

Answer D is incorrect because address translation is not its purpose. It does not satisfy the stem’s governing point: Keep MSDP source discovery separate from the actual multicast user-data forwarding plane.

Answer E is incorrect because MSDP is a control-plane source-discovery mechanism. It does not satisfy the stem’s governing point: Keep MSDP source discovery separate from the actual multicast user-data forwarding plane.