JNCIP-ENT IP Multicast Practice Test 2 — 15 Questions

Question 1

During an audit of a multiregion enterprise network using PIM Sparse-Mode, an engineer needs to ensure that only designated Bootstrap Routers (BSRs) can inject candidate-RP information into the domain. Which Junos configuration feature should be applied on the core routers to secure the BSR domain?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Configure 'set protocols pim interface <interface> bsr-edge' on downstream boundary interfaces.. To protect the PIM domain from rogue BSR messages or unauthorized candidate-RP announcements, Junos allows configuring BSR edge boundaries or using a bsr-candidate policy to filter incoming bootstrap messages.

Answer

Configure an RP-reachability policy under protocols pim static rp.

Answer

Configure 'set protocols pim bsr-candidate interface' with a strict metric.

Answer

Configure a firewall filter on the loopback interface matching PIM protocol traffic destined for 224.0.0.13.

Question 2

An enterprise architect is designing an IP multicast solution using PIM Sparse-Mode and needs to configure a Rendezvous Point (RP) redundantly using Auto-RP. However, Junos OS does not natively support listening to Cisco Auto-RP discovery and announcement messages without specific helper configurations. Which TWO configuration steps are required on Junos to interoperate with or process Auto-RP messages? (Choose two)

Accepted Answer

Configure PIM Dense-Mode on interfaces receiving Auto-RP announcement and discovery multicast groups (224.0.1.39 and 224.0.1.40).. Junos does not natively run Auto-RP (Cisco proprietary). To support Auto-RP environments, Junos routers can be configured to map Auto-RP groups using static RP or by using RPM/helper statements, or by mapping Auto-RP group addresses (224.0.1.39 and 224.0.1.40) into PIM dense-mode or static mappings if supported. Specifically, standard deployments map the Auto-RP well-known group addresses or use static RP configurations since Junos natively relies on standard BSR.

Answer

Enable 'auto-rp compatibility' under the global [edit protocols pim] hierarchy.

Answer

Set the PIM mode to SSM-only across all core interfaces.

Answer

Enable MSDP peering between the Auto-RP mapping agent and the Junos router.

Question 3

An engineer needs to verify the Rendezvous Point (RP) currently learned by a Junos router via the Bootstrap Router (BSR) mechanism. Which operational command should be executed?

Accepted Answer

show pim rps. To check the dynamic RP mappings learned via BSR or static configuration, the command 'show pim join' or 'show pim rps' is used. Specifically, 'show pim rps' displays the active RP database.

Answer

show igmp group

Answer

show multicast route

Answer

show msdp summary

Question 4

An enterprise network administrator is configuring PIM Sparse-Mode and needs to control which multicast groups are allowed to be joined or forwarded through the network. Which THREE methods or configuration elements can be used in Junos OS to filter multicast join messages or control group memberships? (Choose three)

Accepted Answer

Configure an IGMP access policy under [edit protocols igmp interface policy] to restrict local host group memberships.. Option C is correct because an IGMP access policy applied under [edit protocols igmp interface policy] lets the router accept or reject IGMP membership reports from directly attached hosts, thereby restricting which multicast groups local receivers may join. Option D is correct because [edit protocols pim join-policy] applies a routing policy to incoming PIM (*,G) and (S,G) join/prune messages, allowing the administrator to filter which groups or sources PIM will build forwarding state for. Option E is correct because IGMP SSM mapping under [edit protocols igmp ssm-mapping] translates IGMPv1/v2 group joins into (S,G) joins within the SSM range (232.0.0.0/8 by default), effectively controlling which source-specific group memberships are permitted. Option A is not correct because destination port 639 is not a multicast control protocol port (IGMP uses IP protocol 2, PIM uses protocol 103), so a family inet firewall filter matching TCP/UDP port 639 would not filter join messages. Option B is not correct because 01:00:5E:00:00:01 is the Ethernet MAC mapping for 224.0.0.1 (all-hosts), and a bridge-domain filter on that MAC does not filter IGMP/PIM join messages or control PIM-SM group membership in a routed enterprise network.

Answer

Configure a firewall filter family inet filter-name on the loopback interface matching destination port 639.

Answer

Apply a bridge-domain filter under [edit bridge-domains] blocking destination MAC address 01:00:5E:00:00:01.

Question 5

A Junos router is configured with PIM sparse mode and acts as the Rendezvous Point (RP) for the multicast group 239.1.1.1. The network administrator notices that the RP has no (S,G) state for a particular source, yet receivers on the shared tree (*,G) are receiving traffic from that source. Which statement explains this behavior?

Accepted Answer

The source's first-hop router has not sent a PIM register message, so the RP has no (S,G) state, but traffic is still flowing because the RP is also the last-hop router for the group.. In PIM sparse mode, the RP normally maintains (S,G) state for active sources to forward traffic down the shared tree. However, if the RP is also the last-hop router for the group, it will join the shared tree and receive multicast traffic directly from the source's first-hop router via the shared tree. In this scenario, the first-hop router does not need to send PIM register messages because the RP is already on the shared tree, so the RP has no (S,G) state. This is a valid and efficient operation.

Answer

The RP is receiving multicast traffic from the source via a shared tree that was built without the RP's involvement.

Answer

The RP is using the shortest-path tree (SPT) for the source, which bypasses the shared tree.

Answer

The source's first-hop router is not registering with the RP because it is directly connected to the RP.

Question 6

An engineer is deploying PIM Sparse-Mode in a campus network that uses a single static Rendezvous Point (RP) at 10.10.10.10. The design requires that the RP router also be the PIM Designated Router (DR) on the shared LAN segment where the RP address is configured. On the candidate RP router, which configuration is required to ensure the router wins the DR election on interface ge-0/0/1.0?

Accepted Answer

Set the PIM priority to a higher value than other routers on the segment using 'set protocols pim interface ge-0/0/1.0 priority 100'.. In PIM Sparse-Mode, the Designated Router on a multi-access segment is elected based on the highest PIM priority. If priorities are equal, the highest IP address wins. To force the RP router to become the DR, the administrator must set a higher PIM priority on the interface. The other options either lower the priority, change the PIM mode, or use an unrelated metric, none of which would cause the router to win the DR election.

Answer

Set the interface metric to a lower value using 'set protocols pim interface ge-0/0/1.0 metric 1'.

Answer

Enable PIM dense-mode on the interface with 'set protocols pim interface ge-0/0/1.0 mode dense'.

Answer

Configure a lower PIM priority on the interface using 'set protocols pim interface ge-0/0/1.0 priority 1'.

Question 7

A network engineer is troubleshooting a PIM sparse-mode network where receivers are not receiving multicast traffic for group 239.1.1.1. The RP is correctly configured, and the shared tree is built to the RP. The engineer notices that the RP has (S,G) state but the last-hop router does not have (S,G) state. Which statement explains why the last-hop router is not receiving traffic?

Accepted Answer

The last-hop router has not received multicast traffic on the shared tree, so it has not triggered an SPT switchover or Join toward the source.. In PIM sparse-mode, the last-hop router initially joins the shared tree (*,G) rooted at the RP. When it starts receiving multicast traffic on the shared tree, it may switch to the shortest-path tree by sending an (S,G) Join toward the source. If the last-hop router never receives traffic on the shared tree, it will not create (S,G) state. The RP having (S,G) state indicates it has built the source tree, but if the last-hop router isn't receiving traffic, it won't trigger the SPT switchover.

Answer

The RP is not forwarding traffic down the shared tree because it has not received a PIM Register from the first-hop router.

Answer

The last-hop router must send a PIM Join toward the RP to join the shared tree, but it has not done so.

Answer

The last-hop router must send a PIM Assert message to the RP to request the source-specific traffic.

Question 8

An administrator is configuring a Junos router to act as a Candidate Rendezvous Point (C-RP) using the Bootstrap Router (BSR) mechanism for PIM Sparse-Mode. The administrator wants to advertise the router's loopback interface as the RP address for all multicast groups. Which configuration statement is required?

Accepted Answer

set protocols pim rp candidate 10.0.0.1. To configure a Candidate RP for BSR in Junos, the correct statement is 'set protocols pim rp candidate <address>'. This enables the router to advertise itself as a C-RP to the Bootstrap Router, allowing other routers to learn the RP dynamically. The other options are either invalid syntax or configure a static RP, which does not involve BSR.

Answer

set protocols pim rp static 10.0.0.1

Answer

set protocols pim rp bootstrap address 10.0.0.1

Answer

set protocols pim rp local address 10.0.0.1

Question 9

A network engineer is configuring a Bootstrap Router (BSR) in a PIM sparse-mode domain. The engineer wants to ensure that a specific Junos router becomes the BSR and that another router becomes a Candidate-RP (C-RP) for groups 239.1.0.0/16. Which configuration is required on the C-RP router?

Accepted Answer

set protocols pim rp local address 192.168.1.1 group-ranges 239.1.0.0/16. To configure a Candidate-RP for BSR in Junos, the correct statement is 'set protocols pim rp local address 192.168.1.1 group-ranges 239.1.0.0/16'. This advertises the router as a C-RP for the specified group range to the BSR. The BSR collects these advertisements and floods them in Bootstrap messages. Other keywords like 'candidate' or 'static' are not used for this purpose.

Answer

set protocols pim rp candidate 192.168.1.1 group-ranges 239.1.0.0/16

Answer

set protocols pim rp static 192.168.1.1 group-ranges 239.1.0.0/16

Answer

set protocols pim bsr candidate-rp 192.168.1.1 group-ranges 239.1.0.0/16

Question 10

You are deploying PIM sparse-mode in a Junos network where the rendezvous point must be dynamically learned and resilient to a single RP failure without requiring MSDP between the redundant RPs. You plan to use anycast RP with PIM. Which two statements describe how this deployment works on Junos? (Choose two.)

Accepted Answer

Both RPs are configured with the same RP address, typically a shared loopback address, and each advertises it into the unicast routing domain.. Anycast RP gives multiple routers the same RP address, usually a loopback advertised into unicast routing, so each receiver's join reaches the nearest instance. Each instance registers local sources and maintains shared-tree state, and if one fails, unicast convergence redirects joins to another instance. This provides redundancy and load sharing without requiring MSDP between the RPs.

Answer

The RP address must be configured as a static RP on every router because anycast RP cannot be learned dynamically.

Answer

Anycast RP requires that all RPs be placed in the same OSPF area and use identical interface metrics to function.

Answer

The redundant RPs must exchange source-active messages over MSDP so each learns about sources registered with the other.

Question 11

A Junos router running PIM sparse-mode is the first-hop router for source 172.16.5.5 sending to group 239.9.9.9. The RP for the group is reachable, but the RP has no receivers and no shared-tree state for the group. The source's traffic is being encapsulated in PIM register messages, yet the RP is not responding with register-stop. Which statement explains why the register process continues?

Accepted Answer

The RP has no (*,G) or (S,G) state, so it must receive the first data packet via the register before it can decide whether to join the source tree.. In PIM sparse mode, the first-hop router encapsulates the first data packets in register messages and sends them to the RP. If the RP has no state for the group, it cannot immediately send a register-stop; it must receive the register, learn about the source, and decide whether to create state and join the source tree. Only after that evaluation, or when there is no demand and the situation is resolved, does it signal register-stop.

Answer

The first-hop router is sending registers because the source is directly connected and PIM dense-mode fallback is active.

Answer

The RP is not responding because the register message is being dropped by an RPF check on the RP toward the source.

Answer

The first-hop router keeps sending registers until it receives a register-stop, regardless of whether the RP has receivers.

Question 12

A network administrator needs to display the multicast routing table entries, including incoming interfaces and outgoing interface lists (OIL), on a Junos device. Which operational command should be used?

Accepted Answer

show multicast route. The 'show multicast route' command displays the Multicast Forwarding Information Base (MFIB) entries, including source, group, incoming interface, and outgoing interfaces.

Answer

show ospf route

Answer

show igmp interface

Answer

show pim join

Question 13

An administrator wants to configure MSDP (Multicast Source Discovery Protocol) between two autonomous system border routers to share active source information. Which configuration hierarchy in Junos is used to define the MSDP peer relationship?

Accepted Answer

[edit protocols msdp]. MSDP in Junos is configured under the [edit protocols msdp] hierarchy.

Answer

[edit routing-options msdp]

Answer

[edit protocols pim msdp]

Answer

[edit protocols bgp group msdp]

Question 14

An enterprise design requires configuring an Anycast RP setup using two Junos routers to provide redundancy for PIM sparse-mode. Which mechanism is required to synchronize source state information between the two Anycast RPs within the same AS?

Accepted Answer

Multicast Source Discovery Protocol (MSDP). When deploying Anycast RP within a single PIM domain using MSDP, MSDP peer connections are established between the Anycast RP addresses to exchange SA (Source Active) messages, ensuring both RPs know about sources registered to either RP.

Answer

Protocol Independent Multicast Dense-Mode (PIM-DM)

Answer

IGMPv3 snooping

Answer

Multicast BGP (MBGP)

Question 15

Which IPv4 multicast address range is designated for Source-Specific Multicast (SSM) operations according to IANA standards?

Accepted Answer

232.0.0.0/8. The range 232.0.0.0/8 is reserved for Source-Specific Multicast (SSM) by IANA.

Answer

224.0.1.0/24

Answer

224.0.0.0/24

Answer

239.0.0.0/8