Cisco CCNP 350-401 ENCOR Multicast: RPF, PIM-SM, IGMPv2/v3, SSM, Bidir, and MSDP Practice Test 1

 

Topic 12 Practice Test 1 covers Multicast: RPF, PIM-SM, IGMPv2/v3, SSM, Bidir, and MSDP for Cisco 350-401 ENCOR. For broader exam preparation, review the Cisco 350-401 ENCOR Exam Dumps. Every option includes focused technical reasoning explaining both the Cisco enterprise networking concept and its fit to the scenario.

Question 1

A branch deployment team must accept multicast traffic only when it arrives on the interface that unicast routing considers the path back toward the source. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. IGMPv3 INCLUDE mode
  2. RPF check
  3. Anycast RP with MSDP
  4. multicast TTL scope check

Correct Answer(s)

 

B

Rationale

  1. IGMPv3 INCLUDE mode can be appropriate because it lets receivers express source-specific interest needed for SSM behavior. Apply it where a host should receive group traffic from one approved source and reject other senders. This case depends on RPF check, leaving IGMPv3 INCLUDE mode mismatched to the requirement.
  2. RPF check is correct because it uses the unicast routing table or multicast routing information to prevent loops and duplicate forwarding. The stem needs the team to accept multicast traffic only when it arrives on the interface that unicast routing considers the path back toward the source. That fit makes RPF check meet the constraint; alternatives differ materially.
  3. Anycast RP with MSDP works by uses the same RP address on multiple routers and MSDP source-active messages so ASM sources are known across them. It fits where the PIM-SM design requires RP resiliency across separate locations. The required function here is RPF check, so this option targets the wrong condition.
  4. The role of multicast TTL scope check is to verify packets are not expiring before reaching intended receivers. It is useful when routing and PIM state are correct but packets consistently stop after a fixed number of routed hops. Here the design needs RPF check; this choice instead solves an adjacent problem.

 

Question 2

A support organization must provide the rendezvous point used to build the initial shared tree for ASM receivers and sources. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. IGMPv3 EXCLUDE mode
  2. MSDP source-active message
  3. RPF check
  4. PIM sparse-mode RP

Correct Answer(s)

 

D

Rationale

  1. Use IGMPv3 EXCLUDE mode to receive a group from all sources except an identified list. Its mechanism expresses source filtering where particular senders are excluded. The current scenario requires PIM sparse-mode RP; IGMPv3 EXCLUDE mode solves a different design issue.
  2. MSDP source-active message is meant to advertise knowledge of an active multicast source between PIM-SM domains or RP peers. Use it when receivers behind one RP must discover a source registered with another RP. This stem calls for PIM sparse-mode RP; MSDP source-active message addresses another operational need.
  3. RPF check can be appropriate because it uses the unicast routing table or multicast routing information to prevent loops and duplicate forwarding. Apply it where multicast packets arrive on an unexpected interface and are being discarded before downstream replication. This case depends on PIM sparse-mode RP, leaving RPF check mismatched to the requirement.
  4. PIM sparse-mode RP is correct because it anchors (*,G) state so receivers can join a group before source-specific trees are established. The stem needs the team to provide the rendezvous point used to build the initial shared tree for ASM receivers and sources. That fit makes PIM sparse-mode RP meet the constraint; alternatives differ materially.

 

Question 3

A cloud engineering team must carry initial source traffic from the first-hop router toward the RP. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. SSM group range
  2. PIM Register
  3. PIM bidirectional shared tree
  4. PIM sparse-mode RP

Correct Answer(s)

 

B

Rationale

  1. SSM group range works by eliminates RP discovery for SSM traffic and builds (S,G) state directly toward the source. It fits where the application can identify the authorized source address and wants simpler source-specific forwarding. The required function here is PIM Register, so this option targets the wrong condition.
  2. PIM Register is correct because it encapsulates early multicast packets to the RP until native forwarding can take over. The stem needs the team to carry initial source traffic from the first-hop router toward the RP. That fit makes PIM Register meet the constraint; alternatives differ materially.
  3. The role of PIM bidirectional shared tree is to use one shared tree rooted at the RP for traffic in both directions without source-tree switchover. It is useful when many-to-many applications have numerous sources and a shared-tree design is preferred. Here the design needs PIM Register; this choice instead solves an adjacent problem.
  4. The role of PIM sparse-mode RP is to provide the rendezvous point used to build the initial shared tree for ASM receivers and sources. It is useful when an ASM deployment needs a common meeting point for senders and receivers. Here the design needs PIM Register; this choice instead solves an adjacent problem.

 

Question 4

A infrastructure team must represent receiver interest in a multicast group regardless of a particular source. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. PIM SSM without RP
  2. PIM designated router
  3. PIM Register
  4. (*,G) shared-tree state

Correct Answer(s)

 

D

Rationale

  1. PIM SSM without RP is meant to build the tree directly toward the named source instead of using an RP. Use it when an SSM application should not depend on rendezvous-point infrastructure. This stem calls for (*,G) shared-tree state; PIM SSM without RP addresses another operational need.
  2. Use PIM designated router to act for directly connected hosts on a multiaccess network when sending joins or registering sources. Its mechanism elects one PIM router on the LAN to perform first-hop or last-hop control duties. The current scenario requires (*,G) shared-tree state; PIM designated router solves a different design issue.
  3. PIM Register is meant to carry initial source traffic from the first-hop router toward the RP. Use it when a new source begins sending in a PIM-SM domain before the RP has native source-tree state. This stem calls for (*,G) shared-tree state; PIM Register addresses another operational need.
  4. (*,G) shared-tree state is correct because it builds the initial tree toward the RP for any source in the group. The stem needs the team to represent receiver interest in a multicast group regardless of a particular source. That fit makes (*,G) shared-tree state meet the constraint; alternatives differ materially.

 

Question 5

A architecture review board must forward multicast for one specific source and group pair. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. PIM Join toward upstream neighbor
  2. (S,G) source-tree state
  3. last-hop router group state
  4. (*,G) shared-tree state

Correct Answer(s)

 

B

Rationale

  1. Use PIM Join toward upstream neighbor to create or refresh multicast forwarding state toward the source or RP. Its mechanism sends control-plane join messages in the upstream direction selected by RPF. The current scenario requires (S,G) source-tree state; PIM Join toward upstream neighbor solves a different design issue.
  2. (S,G) source-tree state is correct because it creates source-specific state that follows a shortest path toward the source. The stem needs the team to forward multicast for one specific source and group pair. That fit makes (S,G) source-tree state meet the constraint; alternatives differ materially.
  3. last-hop router group state can be appropriate because it combines IGMP information from hosts with PIM signaling toward the multicast distribution tree. Apply it where hosts joined successfully on a VLAN but upstream multicast state is missing. This case depends on (S,G) source-tree state, leaving last-hop router group state mismatched to the requirement.
  4. (*,G) shared-tree state belongs where the last-hop router has joined an ASM group but has not selected a specific source tree. It helps to represent receiver interest in a multicast group regardless of a particular source. The stem instead requires (S,G) source-tree state, so (*,G) shared-tree state does not meet the decisive condition.

 

Question 6

A production operations group must signal host interest in receiving traffic for an IPv4 multicast group. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. PIM Prune
  2. RPF neighbor change after unicast routing change
  3. (S,G) source-tree state
  4. IGMPv2 membership report

Correct Answer(s)

 

D

Rationale

  1. PIM Prune belongs where a branch has no remaining receivers and should stop consuming WAN bandwidth. It helps to remove an unnecessary branch of a multicast distribution tree. The stem instead requires IGMPv2 membership report, so PIM Prune does not meet the decisive condition.
  2. Use RPF neighbor change after unicast routing change to recalculate the valid upstream multicast interface when the route toward the source changes. Its mechanism ties multicast upstream selection to current routing information so topology changes can alter the RPF path. The current scenario requires IGMPv2 membership report; RPF neighbor change after unicast routing change solves a different design issue.
  3. (S,G) source-tree state works by creates source-specific state that follows a shortest path toward the source. It fits where the router has switched from the RP-rooted shared tree to a source-specific path. The required function here is IGMPv2 membership report, so this option targets the wrong condition.
  4. IGMPv2 membership report is correct because it lets the local multicast router learn that receivers exist on the LAN. The stem needs the team to signal host interest in receiving traffic for an IPv4 multicast group. That fit makes IGMPv2 membership report meet the constraint; alternatives differ materially.

 

Question 7

A platform team must notify the local router that a host no longer wants a group so membership can be pruned after verification. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. IGMPv2 leave processing
  2. Anycast RP with MSDP
  3. multicast TTL scope check
  4. IGMPv2 membership report

Correct Answer(s)

 

A

Rationale

  1. IGMPv2 leave processing is correct because it uses leave messages and group-specific queries to determine whether any receivers remain. The stem needs the team to notify the local router that a host no longer wants a group so membership can be pruned after verification. That fit makes IGMPv2 leave processing meet the constraint; alternatives differ materially.
  2. Anycast RP with MSDP works by uses the same RP address on multiple routers and MSDP source-active messages so ASM sources are known across them. It fits where the PIM-SM design requires RP resiliency across separate locations. The required function here is IGMPv2 leave processing, so this option targets the wrong condition.
  3. The role of multicast TTL scope check is to verify packets are not expiring before reaching intended receivers. It is useful when routing and PIM state are correct but packets consistently stop after a fixed number of routed hops. Here the design needs IGMPv2 leave processing; this choice instead solves an adjacent problem.
  4. IGMPv2 membership report can be appropriate because it lets the local multicast router learn that receivers exist on the LAN. Apply it where a host wants to join an ASM group but does not need to specify the source. This case depends on IGMPv2 leave processing, leaving IGMPv2 membership report mismatched to the requirement.

 

Question 8

A network operations group must request traffic only from explicitly listed multicast sources. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. MSDP source-active message
  2. RPF check
  3. IGMPv3 INCLUDE mode
  4. IGMPv2 leave processing

Correct Answer(s)

 

C

Rationale

  1. MSDP source-active message is meant to advertise knowledge of an active multicast source between PIM-SM domains or RP peers. Use it when receivers behind one RP must discover a source registered with another RP. This stem calls for IGMPv3 INCLUDE mode; MSDP source-active message addresses another operational need.
  2. RPF check can be appropriate because it uses the unicast routing table or multicast routing information to prevent loops and duplicate forwarding. Apply it where multicast packets arrive on an unexpected interface and are being discarded before downstream replication. This case depends on IGMPv3 INCLUDE mode, leaving RPF check mismatched to the requirement.
  3. IGMPv3 INCLUDE mode is correct because it lets receivers express source-specific interest needed for SSM behavior. The stem needs the team to request traffic only from explicitly listed multicast sources. That fit makes IGMPv3 INCLUDE mode meet the constraint; alternatives differ materially.
  4. Use IGMPv2 leave processing to notify the local router that a host no longer wants a group so membership can be pruned after verification. Its mechanism uses leave messages and group-specific queries to determine whether any receivers remain. The current scenario requires IGMPv3 INCLUDE mode; IGMPv2 leave processing solves a different design issue.

 

Question 9

A application team must receive a group from all sources except an identified list. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. PIM bidirectional shared tree
  2. IGMPv3 EXCLUDE mode
  3. PIM sparse-mode RP
  4. IGMPv3 INCLUDE mode

Correct Answer(s)

 

B

Rationale

  1. The role of PIM bidirectional shared tree is to use one shared tree rooted at the RP for traffic in both directions without source-tree switchover. It is useful when many-to-many applications have numerous sources and a shared-tree design is preferred. Here the design needs IGMPv3 EXCLUDE mode; this choice instead solves an adjacent problem.
  2. IGMPv3 EXCLUDE mode is correct because it expresses source filtering where particular senders are excluded. The stem needs the team to receive a group from all sources except an identified list. That fit makes IGMPv3 EXCLUDE mode meet the constraint; alternatives differ materially.
  3. The role of PIM sparse-mode RP is to provide the rendezvous point used to build the initial shared tree for ASM receivers and sources. It is useful when an ASM deployment needs a common meeting point for senders and receivers. Here the design needs IGMPv3 EXCLUDE mode; this choice instead solves an adjacent problem.
  4. IGMPv3 INCLUDE mode belongs where a host should receive group traffic from one approved source and reject other senders. It helps to request traffic only from explicitly listed multicast sources. The stem instead requires IGMPv3 EXCLUDE mode, so IGMPv3 INCLUDE mode does not meet the decisive condition.

 

Question 10

A enterprise architect must use source-specific multicast semantics where the receiver identifies both source and group. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. SSM group range
  2. PIM designated router
  3. PIM Register
  4. IGMPv3 EXCLUDE mode

Correct Answer(s)

 

A

Rationale

  1. SSM group range is correct because it eliminates RP discovery for SSM traffic and builds (S,G) state directly toward the source. The stem needs the team to use source-specific multicast semantics where the receiver identifies both source and group. That fit makes SSM group range meet the constraint; alternatives differ materially.
  2. Use PIM designated router to act for directly connected hosts on a multiaccess network when sending joins or registering sources. Its mechanism elects one PIM router on the LAN to perform first-hop or last-hop control duties. The current scenario requires SSM group range; PIM designated router solves a different design issue.
  3. PIM Register is meant to carry initial source traffic from the first-hop router toward the RP. Use it when a new source begins sending in a PIM-SM domain before the RP has native source-tree state. This stem calls for SSM group range; PIM Register addresses another operational need.
  4. IGMPv3 EXCLUDE mode is meant to receive a group from all sources except an identified list. Use it when a receiver wants broad ASM-style group traffic but must block a small set of sources. This stem calls for SSM group range; IGMPv3 EXCLUDE mode addresses another operational need.

 

Question 11

A site reliability team must build the tree directly toward the named source instead of using an RP. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. last-hop router group state
  2. (*,G) shared-tree state
  3. PIM SSM without RP
  4. SSM group range

Correct Answer(s)

 

C

Rationale

  1. last-hop router group state can be appropriate because it combines IGMP information from hosts with PIM signaling toward the multicast distribution tree. Apply it where hosts joined successfully on a VLAN but upstream multicast state is missing. This case depends on PIM SSM without RP, leaving last-hop router group state mismatched to the requirement.
  2. (*,G) shared-tree state belongs where the last-hop router has joined an ASM group but has not selected a specific source tree. It helps to represent receiver interest in a multicast group regardless of a particular source. The stem instead requires PIM SSM without RP, so (*,G) shared-tree state does not meet the decisive condition.
  3. PIM SSM without RP is correct because it relies on receiver source information, typically from IGMPv3, to create (S,G) joins. The stem needs the team to build the tree directly toward the named source instead of using an RP. That fit makes PIM SSM without RP meet the constraint; alternatives differ materially.
  4. SSM group range can be appropriate because it eliminates RP discovery for SSM traffic and builds (S,G) state directly toward the source. Apply it where the application can identify the authorized source address and wants simpler source-specific forwarding. This case depends on PIM SSM without RP, leaving SSM group range mismatched to the requirement.

 

Question 12

A security engineering group must create or refresh multicast forwarding state toward the source or RP. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. PIM Join toward upstream neighbor
  2. RPF neighbor change after unicast routing change
  3. (S,G) source-tree state
  4. PIM SSM without RP

Correct Answer(s)

 

A

Rationale

  1. PIM Join toward upstream neighbor is correct because it sends control-plane join messages in the upstream direction selected by RPF. The stem needs the team to create or refresh multicast forwarding state toward the source or RP. That fit makes PIM Join toward upstream neighbor meet the constraint; alternatives differ materially.
  2. Use RPF neighbor change after unicast routing change to recalculate the valid upstream multicast interface when the route toward the source changes. Its mechanism ties multicast upstream selection to current routing information so topology changes can alter the RPF path. The current scenario requires PIM Join toward upstream neighbor; RPF neighbor change after unicast routing change solves a different design issue.
  3. (S,G) source-tree state works by creates source-specific state that follows a shortest path toward the source. It fits where the router has switched from the RP-rooted shared tree to a source-specific path. The required function here is PIM Join toward upstream neighbor, so this option targets the wrong condition.
  4. The role of PIM SSM without RP is to build the tree directly toward the named source instead of using an RP. It is useful when an SSM application should not depend on rendezvous-point infrastructure. Here the design needs PIM Join toward upstream neighbor; this choice instead solves an adjacent problem.

 

Question 13

A branch deployment team must remove an unnecessary branch of a multicast distribution tree. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. PIM Prune
  2. multicast TTL scope check
  3. IGMPv2 membership report
  4. PIM Join toward upstream neighbor

Correct Answer(s)

 

A

Rationale

  1. PIM Prune is correct because it signals that a downstream path no longer needs traffic for the relevant multicast state. The stem needs the team to remove an unnecessary branch of a multicast distribution tree. That fit makes PIM Prune meet the constraint; alternatives differ materially.
  2. The role of multicast TTL scope check is to verify packets are not expiring before reaching intended receivers. It is useful when routing and PIM state are correct but packets consistently stop after a fixed number of routed hops. Here the design needs PIM Prune; this choice instead solves an adjacent problem.
  3. IGMPv2 membership report can be appropriate because it lets the local multicast router learn that receivers exist on the LAN. Apply it where a host wants to join an ASM group but does not need to specify the source. This case depends on PIM Prune, leaving IGMPv2 membership report mismatched to the requirement.
  4. PIM Join toward upstream neighbor is meant to create or refresh multicast forwarding state toward the source or RP. Use it when a downstream router has interested receivers and must extend the multicast tree upstream. This stem calls for PIM Prune; PIM Join toward upstream neighbor addresses another operational need.

 

Question 14

A support organization must provide redundant RP addresses while synchronizing active-source knowledge between RP peers. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. RPF check
  2. IGMPv2 leave processing
  3. Anycast RP with MSDP
  4. PIM Prune

Correct Answer(s)

 

C

Rationale

  1. RPF check can be appropriate because it uses the unicast routing table or multicast routing information to prevent loops and duplicate forwarding. Apply it where multicast packets arrive on an unexpected interface and are being discarded before downstream replication. This case depends on Anycast RP with MSDP, leaving RPF check mismatched to the requirement.
  2. Use IGMPv2 leave processing to notify the local router that a host no longer wants a group so membership can be pruned after verification. Its mechanism uses leave messages and group-specific queries to determine whether any receivers remain. The current scenario requires Anycast RP with MSDP; IGMPv2 leave processing solves a different design issue.
  3. Anycast RP with MSDP is correct because it uses the same RP address on multiple routers and MSDP source-active messages so ASM sources are known across them. The stem needs the team to provide redundant RP addresses while synchronizing active-source knowledge between RP peers. That fit makes Anycast RP with MSDP meet the constraint; alternatives differ materially.
  4. PIM Prune works by signals that a downstream path no longer needs traffic for the relevant multicast state. It fits where a branch has no remaining receivers and should stop consuming WAN bandwidth. The required function here is Anycast RP with MSDP, so this option targets the wrong condition.

 

Question 15

A cloud engineering team must advertise knowledge of an active multicast source between PIM-SM domains or RP peers. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. PIM sparse-mode RP
  2. IGMPv3 INCLUDE mode
  3. Anycast RP with MSDP
  4. MSDP source-active message

Correct Answer(s)

 

D

Rationale

  1. The role of PIM sparse-mode RP is to provide the rendezvous point used to build the initial shared tree for ASM receivers and sources. It is useful when an ASM deployment needs a common meeting point for senders and receivers. Here the design needs MSDP source-active message; this choice instead solves an adjacent problem.
  2. IGMPv3 INCLUDE mode belongs where a host should receive group traffic from one approved source and reject other senders. It helps to request traffic only from explicitly listed multicast sources. The stem instead requires MSDP source-active message, so IGMPv3 INCLUDE mode does not meet the decisive condition.
  3. Anycast RP with MSDP can be appropriate because it uses the same RP address on multiple routers and MSDP source-active messages so ASM sources are known across them. Apply it where the PIM-SM design requires RP resiliency across separate locations. This case depends on MSDP source-active message, leaving Anycast RP with MSDP mismatched to the requirement.
  4. MSDP source-active message is correct because it carries source/group information so another RP can learn about remote active sources. The stem needs the team to advertise knowledge of an active multicast source between PIM-SM domains or RP peers. That fit makes MSDP source-active message meet the constraint; alternatives differ materially.

 

Question 16

A infrastructure team must use one shared tree rooted at the RP for traffic in both directions without source-tree switchover. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. PIM bidirectional shared tree
  2. PIM Register
  3. IGMPv3 EXCLUDE mode
  4. MSDP source-active message

Correct Answer(s)

 

A

Rationale

  1. PIM bidirectional shared tree is correct because it maintains bidirectional group forwarding around a designated forwarder model. The stem needs the team to use one shared tree rooted at the RP for traffic in both directions without source-tree switchover. That fit makes PIM bidirectional shared tree meet the constraint; alternatives differ materially.
  2. PIM Register is meant to carry initial source traffic from the first-hop router toward the RP. Use it when a new source begins sending in a PIM-SM domain before the RP has native source-tree state. This stem calls for PIM bidirectional shared tree; PIM Register addresses another operational need.
  3. IGMPv3 EXCLUDE mode is meant to receive a group from all sources except an identified list. Use it when a receiver wants broad ASM-style group traffic but must block a small set of sources. This stem calls for PIM bidirectional shared tree; IGMPv3 EXCLUDE mode addresses another operational need.
  4. The role of MSDP source-active message is to advertise knowledge of an active multicast source between PIM-SM domains or RP peers. It is useful when receivers behind one RP must discover a source registered with another RP. Here the design needs PIM bidirectional shared tree; this choice instead solves an adjacent problem.

 

Question 17

A architecture review board must act for directly connected hosts on a multiaccess network when sending joins or registering sources. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. (*,G) shared-tree state
  2. SSM group range
  3. PIM bidirectional shared tree
  4. PIM designated router

Correct Answer(s)

 

D

Rationale

  1. (*,G) shared-tree state belongs where the last-hop router has joined an ASM group but has not selected a specific source tree. It helps to represent receiver interest in a multicast group regardless of a particular source. The stem instead requires PIM designated router, so (*,G) shared-tree state does not meet the decisive condition.
  2. SSM group range can be appropriate because it eliminates RP discovery for SSM traffic and builds (S,G) state directly toward the source. Apply it where the application can identify the authorized source address and wants simpler source-specific forwarding. This case depends on PIM designated router, leaving SSM group range mismatched to the requirement.
  3. Use PIM bidirectional shared tree to use one shared tree rooted at the RP for traffic in both directions without source-tree switchover. Its mechanism maintains bidirectional group forwarding around a designated forwarder model. The current scenario requires PIM designated router; PIM bidirectional shared tree solves a different design issue.
  4. PIM designated router is correct because it elects one PIM router on the LAN to perform first-hop or last-hop control duties. The stem needs the team to act for directly connected hosts on a multiaccess network when sending joins or registering sources. That fit makes PIM designated router meet the constraint; alternatives differ materially.

 

Question 18

A production operations group must track local receiver membership and translate it into upstream PIM joins. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. (S,G) source-tree state
  2. last-hop router group state
  3. PIM SSM without RP
  4. PIM designated router

Correct Answer(s)

 

B

Rationale

  1. (S,G) source-tree state works by creates source-specific state that follows a shortest path toward the source. It fits where the router has switched from the RP-rooted shared tree to a source-specific path. The required function here is last-hop router group state, so this option targets the wrong condition.
  2. last-hop router group state is correct because it combines IGMP information from hosts with PIM signaling toward the multicast distribution tree. The stem needs the team to track local receiver membership and translate it into upstream PIM joins. That fit makes last-hop router group state meet the constraint; alternatives differ materially.
  3. The role of PIM SSM without RP is to build the tree directly toward the named source instead of using an RP. It is useful when an SSM application should not depend on rendezvous-point infrastructure. Here the design needs last-hop router group state; this choice instead solves an adjacent problem.
  4. PIM designated router is meant to act for directly connected hosts on a multiaccess network when sending joins or registering sources. Use it when several PIM routers share one Ethernet segment with multicast sources and receivers. This stem calls for last-hop router group state; PIM designated router addresses another operational need.

 

Question 19

A platform team must recalculate the valid upstream multicast interface when the route toward the source changes. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. IGMPv2 membership report
  2. PIM Join toward upstream neighbor
  3. RPF neighbor change after unicast routing change
  4. last-hop router group state

Correct Answer(s)

 

C

Rationale

  1. IGMPv2 membership report can be appropriate because it lets the local multicast router learn that receivers exist on the LAN. Apply it where a host wants to join an ASM group but does not need to specify the source. This case depends on RPF neighbor change after unicast routing change, leaving IGMPv2 membership report mismatched to the requirement.
  2. PIM Join toward upstream neighbor is meant to create or refresh multicast forwarding state toward the source or RP. Use it when a downstream router has interested receivers and must extend the multicast tree upstream. This stem calls for RPF neighbor change after unicast routing change; PIM Join toward upstream neighbor addresses another operational need.
  3. RPF neighbor change after unicast routing change is correct because it ties multicast upstream selection to current routing information so topology changes can alter the RPF path. The stem needs the team to recalculate the valid upstream multicast interface when the route toward the source changes. That fit makes RPF neighbor change after unicast routing change meet the constraint; alternatives differ materially.
  4. last-hop router group state belongs where hosts joined successfully on a VLAN but upstream multicast state is missing. It helps to track local receiver membership and translate it into upstream PIM joins. The stem instead requires RPF neighbor change after unicast routing change, so last-hop router group state does not meet the decisive condition.

 

Question 20

A network operations group must verify packets are not expiring before reaching intended receivers. Which approach most directly satisfies the stated requirement? Choose ONE.

  1. IGMPv2 leave processing
  2. PIM Prune
  3. multicast TTL scope check
  4. RPF neighbor change after unicast routing change

Correct Answer(s)

 

C

Rationale

  1. Use IGMPv2 leave processing to notify the local router that a host no longer wants a group so membership can be pruned after verification. Its mechanism uses leave messages and group-specific queries to determine whether any receivers remain. The current scenario requires multicast TTL scope check; IGMPv2 leave processing solves a different design issue.
  2. PIM Prune works by signals that a downstream path no longer needs traffic for the relevant multicast state. It fits where a branch has no remaining receivers and should stop consuming WAN bandwidth. The required function here is multicast TTL scope check, so this option targets the wrong condition.
  3. multicast TTL scope check is correct because it examines IP TTL handling because multicast forwarding decrements TTL like other IP traffic. The stem needs the team to verify packets are not expiring before reaching intended receivers. That fit makes multicast TTL scope check meet the constraint; alternatives differ materially.
  4. RPF neighbor change after unicast routing change is meant to recalculate the valid upstream multicast interface when the route toward the source changes. Use it when an IGP reconvergence moves the best path to the multicast source onto a different interface. This stem calls for multicast TTL scope check; RPF neighbor change after unicast routing change addresses another operational need.

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