JNCIP-ENT IP Multicast Practice Test 3 — 15 Questions

Question 1

An enterprise engineer is configuring Multicast Source Discovery Protocol (MSDP) on a Junos device. Which THREE statements accurately describe MSDP behavior and functions? (Choose three)

Accepted Answer

MSDP uses Source-Active (SA) messages to advertise active multicast sources to peer RPs.. MSDP is used between RPs to share active sources, uses TCP for transport, and uses SA (Source-Active) messages.

Answer

MSDP replaces PIM sparse-mode for forwarding multicast data traffic to receivers.

Answer

MSDP runs directly over IP protocol number 46.

Question 2

An engineer is troubleshooting multicast forwarding and RPF failures on a Junos routing instance. Which THREE conditions will cause a multicast RPF check failure? (Choose three)

Accepted Answer

The route to the source points towards a null or reject route.. RPF failures occur when the incoming interface for a multicast packet does not match the reverse path towards the source in the routing table, when no route exists, or when the routing table source differs.

Answer

IGMPv2 leave messages are received on an interface without active listeners.

Answer

PIM hello messages are exchanged with an incorrect hold time.

Question 3

An administrator is designing a high-availability PIM sparse-mode network. Which THREE mechanisms are used to provide redundancy for Rendezvous Points (RPs)? (Choose three)

Accepted Answer

Anycast RP with MSDP peering between multiple RPs. RP redundancy is typically achieved using static Anycast RP with MSDP, Bootstrap Router (BSR) dynamic discovery with multiple Candidate RPs, or Auto-RP (vendor-specific).

Answer

IGMP snooping querier election redundancy across core switches

Answer

Static RP configuration with multiple backup RP IP addresses configured on every router

Question 4

An enterprise network uses MBGP (Multicast BGP) alongside PIM sparse-mode. Which THREE statements accurately describe the function of MBGP in a multicast environment? (Choose three)

Accepted Answer

MBGP allows the multicast routing topology to be different from the unicast routing topology.. MBGP provides separate multicast routing information for RPF checks, uses address families (AFI/SAFI), and allows multicast topology to differ from unicast topology.

Answer

MBGP replaces the function of MSDP by sharing source-active states between RPs.

Answer

MBGP forwards multicast data packets directly across autonomous systems.

Question 5

Which TWO statements are true regarding Source-Specific Multicast (SSM) operation in Junos? (Choose two)

Accepted Answer

SSM eliminates the need for Rendezvous Points (RPs) and MSDP.. SSM uses the 232.0.0.0/8 range and requires IGMPv3 (or MLDv2 for IPv6) to allow hosts to specify source addresses directly, bypassing the need for an RP.

Answer

SSM requires PIM dense-mode to flood traffic to all routers.

Answer

SSM operates within the 224.0.0.0/24 multicast range.

Answer

SSM uses (*,G) shared trees exclusively for distribution.

Question 6

An administrator is configuring IGMP snooping on an EX Series switch. Which TWO benefits does IGMP snooping provide in a switched Ethernet environment? (Choose two)

Accepted Answer

It conserves bandwidth on switch links by filtering unwanted multicast streams.. IGMP snooping inspects IGMP traffic to constrain multicast traffic to ports with active receivers, preventing unnecessary flooding on non-listening ports.

Answer

It automatically acts as the PIM Rendezvous Point for the VLAN.

Answer

It translates IPv4 multicast addresses to IPv6 multicast addresses.

Answer

It replaces PIM sparse-mode on Layer 3 core routers.

Question 7

Which TWO statements correctly describe the role of the Designated Router (DR) on a multi-access network running PIM sparse-mode? (Choose two)

Accepted Answer

The DR sends PIM join and prune messages towards the RP on behalf of local receivers when necessary.. The PIM DR is responsible for sending register messages to the RP on behalf of sources and sending join/prune messages on behalf of receivers on a shared LAN segment.

Answer

The DR elects the IGMP querier for the VLAN segment.

Answer

The DR maintains the MSDP Source-Active cache for the entire AS.

Answer

The DR floods all multicast traffic across the multi-access segment by default.

Question 8

An engineer is troubleshooting PIM Sparse-Mode on a Junos device and notices that source traffic is not switching from the shared tree (*,G) to the shortest path tree (S,G) at the Last-Hop Router. Which configuration statement on the Junos routing instance allows adjusting the threshold for this switchover behavior?

Accepted Answer

set protocols pim spt-threshold infinity. By default, Junos switches from the (*,G) shared tree to the (S,G) shortest path tree immediately upon receiving the first data packet from a source. To prevent this or adjust the behavior, operators use the 'spt-threshold' statement under protocols pim.

Answer

set routing-options multicast spt-lifetime 0

Answer

set protocols pim switchover-delay 0

Answer

set protocols igmp ssm-mapping

Question 9

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?

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 10

An administrator is configuring a Junos device to support IGMPv3 on user-facing VLAN interfaces. Which configuration statement enables IGMPv3 processing on interface irb.10?

Accepted Answer

set protocols igmp interface irb.10 version 3. IGMP version selection on Junos interfaces is configured under protocols igmp interface.

Answer

set protocols pim interface irb.10 igmp-version 3

Answer

set interfaces irb.10 family inet igmp-version v3

Answer

set routing-options multicast igmp-version 3

Question 11

A network engineer must implement Anycast RP using MSDP between two data center routers running Junos OS. Which statement correctly describes a core requirement for MSDP peer establishment?

Accepted Answer

MSDP peer addresses must be reachable via standard unicast routing protocols, and TCP port 639 must be allowed.. MSDP sessions run over TCP port 639. Unlike PIM, MSDP peers do not require direct physical connectivity and typically peer using their loopback addresses, requiring an IGP and an underlying unicast route to establish the TCP connection.

Answer

MSDP messages are encapsulated in PIM register packets and sent directly to the multicast group 224.0.0.13.

Answer

MSDP relies on IGMPv3 source filters to exchange active source state information across administrative domains.

Answer

MSDP peering sessions require direct physical interface connectivity between the Anycast RP routers.

Question 12

An enterprise has deployed MSDP between two independent PIM sparse-mode domains. An administrator notices that Source-Active (SA) messages are looping between MSDP peers. Which Junos mechanism should be configured to prevent SA message loops in an MSDP topology?

Accepted Answer

Configure an MSDP mesh group using 'set protocols msdp mesh-group <name>'.. MSDP uses a modified Reverse Path Forwarding (RPF) check for SA messages. To prevent loops in complex topologies, peer RPF flooding rules or MSDP mesh groups are configured using 'set protocols msdp mesh-group'.

Answer

Configure static RPF routes pointing to the peer loopbacks.

Answer

Enable PIM Dense-Mode on the interconnecting links between the MSDP peers.

Answer

Apply a TTL scoping boundary on the MSDP TCP sessions.

Question 13

A network administrator is configuring an enterprise router to join the Source-Specific Multicast (SSM) range. According to RFC standards, what is the standard IPv4 address block reserved for SSM?

Accepted Answer

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

Answer

239.0.0.0/8

Answer

224.0.0.0/24

Answer

224.0.1.0/24

Question 14

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 15

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