JNCIP-ENT IP Multicast Practice Test 3 — 15 Questions

Question 1

An engineer configures protocol independent multicast (PIM) sparse-mode on a Junos device and notices that join messages are not reaching the Rendezvous Point (RP). Which CLI command should the engineer use to verify the operational state of the PIM neighbor adjacencies and confirm that the hello messages are successfully exchanged?

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

Accepted Answer

show pim neighbor. The 'show pim neighbor' command is the standard operational command in Junos to verify active PIM neighbor adjacencies, IP addresses, interfaces, and hold timers.

Answer

show mpls lsp

Answer

show rpc statistics

Answer

show igmp group

Question 2

An engineer needs to view the MSDP Source-Active (SA) cache on a Junos router to verify which sources are currently active across different PIM domains. Which operational command should be executed?

Accepted Answer

show msdp source-active. The 'show msdp source-active' command displays the contents of the MSDP SA cache.

Answer

show multicast source-cache

Answer

show bgp msdp active

Answer

show pim source-active

Question 3

An engineer needs to verify which multicast groups have active receivers joined on an interface using IGMP. Which operational command should be used?

Accepted Answer

show igmp group. The 'show igmp group' command lists the multicast groups joined on interfaces via IGMP.

Answer

show multicast heap

Answer

show msdp SA-cache

Answer

show pim rp statistics

Question 4

Which operational command is used to verify the operational status and peer state of MSDP sessions on a Junos device?

Accepted Answer

show msdp summary. The 'show msdp summary' command provides an overview of MSDP peers, state, and connection status.

Answer

show igmp summary

Answer

show pim summary

Answer

show multicast summary

Question 5

An administrator wants to configure Candidate-RP (C-RP) advertisements using the Bootstrap Router (BSR) mechanism in PIM sparse-mode. Which hierarchy level in Junos is used to configure the local router as a Candidate-RP?

Accepted Answer

[edit protocols pim candidate-rp]. Candidate RPs in Junos are configured under protocols pim candidate-rp.

Answer

[edit protocols pim bsr]

Answer

[edit routing-options candidate-rp]

Answer

[edit protocols igmp candidate-rp]

Question 6

Which protocol version introduces explicit source inclusion and exclusion lists (TO_EX, TO_IN, IS_IN, IS_EX) in membership reports?

Accepted Answer

IGMPv3. IGMPv2 supports basic group membership, whereas IGMPv3 introduces source-filtering capabilities allowing hosts to specify include or exclude source lists.

Answer

IGMPv2

Answer

IGMPv4

Answer

IGMPv1

Question 7

An administrator wants to configure an MSDP peer relationship on a Junos device and ensure that the MD5 password authentication is applied to the TCP session. Where is the MD5 authentication key configured for an MSDP peer?

Accepted Answer

set protocols msdp peer

authentication-key . MSDP authentication keys are configured under the specific MSDP peer statement using the authentication-key option.

Answer

set system authentication-key <key>

Answer

set protocols pim peer

authentication-key

Answer

set routing-options msdp authentication-key <key>

Question 8

Which IPv4 address is assigned as the all-systems multicast group address, used by routers to query all hosts on a local subnet?

Accepted Answer

224.0.0.1. 224.0.0.1 is the all-hosts (all-systems) multicast group address.

Answer

224.0.0.22

Answer

224.0.0.13

Answer

224.0.0.2

Question 9

An enterprise design uses PIM sparse-mode with a BSR. An engineer notices that the router has successfully elected a BSR, but no Candidate-RP messages are being processed. Which operational command should the engineer use to verify the BSR candidate information and elected BSR address on the router?

Accepted Answer

show pim bsr statistics. The 'show pim bsr local' or 'show pim bsr' commands display information regarding the BSR state, elected BSR, and received bootstrap messages.

Answer

show igmp bsr

Answer

show msdp bsr-state

Answer

show multicast bsr

Question 10

An engineer wants to configure a Junos router to act as a Bootstrap Router (BSR) for PIM sparse-mode. Which configuration hierarchy is used to enable the BSR function?

Accepted Answer

[edit protocols pim bsr]. BSR functionality on Junos is configured under protocols pim bsr.

Answer

[edit protocols msdp bsr]

Answer

[edit routing-options bsr]

Answer

[edit protocols pim candidate-rp]

Question 11

An enterprise network uses multiple routing instances with PIM sparse-mode. An engineer needs to configure Inter-AS multicast routing using MSDP. Which component is required to establish MSDP peering across different autonomous systems where BGP is also running?

Accepted Answer

Matching MSDP peer loopback addresses and TCP session establishment with MBGP routing. MSDP peers can be configured between BGP speakers in different ASs. The MSDP peer address often matches the BGP router ID or loopback, and MBGP supplies the RPF route for the source.

Answer

A shared PIM dense-mode tunnel between the AS border routers

Answer

IGMPv2 proxy configuration on the border routers

Answer

Static multicast routes for all 224.0.0.0/4 destinations

Question 12

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

Accepted Answer

show pim rps. The 'show pim rps' command displays all active RPs known to the router, including whether they were learned via static configuration, Auto-RP, or BSR.

Answer

show igmp rp

Answer

show msdp rp-list

Answer

show multicast rp-table

Question 13

An engineer is configuring PIM sparse-mode in an enterprise network. Which TWO characteristics are true regarding PIM sparse-mode operation? (Choose two)

Accepted Answer

It uses explicit join messages (*,G or S,G) sent towards the RP or source.. Option C is correct because PIM-SM is an explicit-join protocol: receivers' DRs send (*,G) joins toward the Rendezvous Point and, after the shortest-path tree switchover, (S,G) joins toward the source, building distribution trees only where membership exists. Option E is correct because PIM-SM uses a shared tree rooted at the RP to connect sources and receivers initially, with the RP forwarding traffic until routers can join the source-specific shortest-path tree. Option A is wrong because PIM-SM does not mandate IGMPv3 on every interface; IGMPv2 or IGMPv3 may be used, and IGMP is only relevant on receiver-facing segments. Option B is wrong because flooding-until-pruned behavior describes PIM dense mode, not sparse mode. Option D is wrong because PIM-SM relies on the unicast routing table (or MRIB) for RPF checks to prevent loops and select the correct upstream neighbor.

Answer

It requires every interface to run IGMPv3 exclusively.

Answer

It floods multicast traffic across all router interfaces by default until pruned.

Answer

It does not require any unicast routing protocol for RPF checks.

Question 14

An administrator is troubleshooting an MSDP deployment between two autonomous systems. Which THREE factors can cause an MSDP peer session to fail to establish? (Choose three)

Accepted Answer

TCP port 639 being blocked by a firewall between the peers. MSDP runs over TCP port 639. Session establishment requires correct peer IP configuration, functional TCP connectivity, and matching authentication keys if configured.

Answer

An incorrect IGMPv2 timer setting on the receiver VLAN

Answer

An invalid PIM dense-mode setting on the core interface

Question 15

Which TWO statements are correct regarding IGMP version 2 (IGMPv2) features compared to IGMPv1? (Choose two)

Accepted Answer

IGMPv2 includes a querier election mechanism among multiple routers on a subnet.. Option B is correct because IGMPv2 adds a querier election process: when multiple multicast routers exist on the same subnet, the one with the lowest source IP address on that subnet is elected as the querier, whereas IGMPv1 designated the querier via the multicast routing protocol (e.g., PIM). Option C is correct because IGMPv2 introduces the explicit Leave Group message (type 0x17), sent to the all-routers address 224.0.0.2, which allows the querier to send a group-specific query and prune the group quickly instead of waiting for the full group membership timeout. Option A is wrong because IGMPv2 specifically reduces reliance on the membership timeout by using the Leave Group message, though the timeout still exists as a fallback. Option D is wrong because source-specific include/exclude filtering is an IGMPv3 feature, not IGMPv2. Option E is wrong because IGMPv2 is a host-to-router protocol that does not require PIM sparse-mode on hosts; PIM is a router-to-router multicast routing protocol.

Answer

IGMPv2 relies entirely on group membership timeout for leaving groups.

Answer

IGMPv2 supports source-specific filtering lists (include/exclude).

Answer

IGMPv2 requires PIM sparse-mode to be enabled on all participating hosts.