JNCIP-ENT IP Multicast — Timed 10 Questions

Question 1

In an enterprise network running PIM sparse-mode, an engineer notices that multicast traffic is switched from the shared tree (*,G) to the source-specific tree (S,G) prematurely, causing micro-bursts on core links. Which command disables this automatic switchover behavior on a Junos router?

10 minute time limit — choose an answer to begin.

Accepted Answer

set protocols pim spt-threshold infinity. By default, last-hop routers switch from (*,G) to (S,G) upon receiving the first packet from source S. To prevent this, the 'spt-threshold infinity' command is configured under [edit protocols pim].

Answer

set routing-options multicast spt-mode disable

Answer

set protocols pim disable-spt-switchover

Answer

set protocols igmp spt-threshold 0

Question 2

An enterprise network uses PIM sparse-mode across multiple routing instances. An administrator notices that source registration messages are looping between the designated router (DR) and the RP. Which configuration statement under [edit protocols pim] will prevent the DR from continuously encapsulating and sending register messages when no receivers are joined?

Accepted Answer

set protocols pim rp static address 192.168.1.1. Using register-suppression or configuring an MSDP peer is common, but on the Junos DR side, ensuring proper register-policy or verifying register-stop timers helps. However, Juniper implements register-suppression by default via register-stop messages from the RP. To alter register behavior, register-policy can be applied.

Answer

set protocols pim interface all no-bsr

Answer

set protocols pim rp static address 192.168.1.1 register-policy REJECT-REG

Answer

set protocols pim rp static address 192.168.1.1 no-registration-suppression

Question 3

An engineer wants to restrict IGMP membership reports to only accept version 2 on a specific VLAN interface configured on an MX Series router. Which configuration statement achieves this requirement?

Accepted Answer

set protocols igmp interface vlan.10 version 2. Junos allows configuring specific IGMP versions per interface under protocols igmp interface.

Answer

set protocols pim interface vlan.10 igmp-version 2

Answer

set routing-options multicast igmp-version 2 interface vlan.10

Answer

set interfaces vlan.10 igmp-version 2

Question 4

An administrator wants to configure a static Rendezvous Point (RP) with IP address 192.168.100.1 for all multicast groups on a Junos router. Which configuration accomplishes this?

Accepted Answer

set protocols pim rp static address 192.168.100.1. Static RPs are defined under protocols pim rp static address. Group ranges can also be specified.

Answer

set routing-options multicast rp 192.168.100.1

Answer

set protocols pim static-rp address 192.168.100.1

Answer

set protocols igmp rp address 192.168.100.1

Question 5

An enterprise administrator wants to limit PIM sparse-mode join messages to prevent unauthorized sources from registering. Where should a policy be applied to filter PIM join/prune messages in Junos?

Accepted Answer

set protocols pim import <policy-name>. PIM join/prune filtering is accomplished by applying a import policy under protocols pim.

Answer

set protocols igmp import <policy-name>

Answer

set routing-options pim-policy <policy-name>

Answer

set interfaces all unit 0 family pim filter input <policy-name>

Question 6

Which configuration statement enables PIM sparse-mode globally across all interfaces in a Junos routing instance?

Accepted Answer

set protocols pim interface all. In Junos, PIM can be enabled on individual interfaces or globally by specifying 'interface all' under protocols pim.

Answer

set routing-options multicast pim-enable

Answer

set protocols multicast enable

Answer

set protocols pim interface all mode sparse

Question 7

A network engineer troubleshoots an issue where multicast data packets are being dropped due to an RPF (Reverse Path Forwarding) check failure. The unicast routing table uses OSPF, but MBGP is deployed for multicast routing. Which operational command should the engineer use to verify the multicast RPF path for a specific source IP?

Accepted Answer

show route rpf 192.0.2.1. When MBGP is used for multicast RPF separate from unicast routing, the command 'show route rpf <source-ip>' helps check which routing table and next-hop is used for the multicast RPF check.

Answer

show msdp rpf 192.0.2.1

Answer

show pim rpf-table 192.0.2.1

Answer

show multicast rpf-failure

Question 8

An administrator configures MSDP peering between two routers. After configuration, the MSDP session remains in the 'Connect' or 'Active' state and never transitions to 'Established'. Which underlying protocol dependency must be verified and operational for MSDP sessions to establish?

Accepted Answer

TCP connectivity on port 639 between the MSDP peers. MSDP relies directly on TCP (TCP port 639) to establish peer connections. If TCP connectivity fails, the MSDP state will not reach Established.

Answer

MBGP unicast routing tables synchronized

Answer

PIM dense-mode adjacency between the peers

Answer

IGMPv3 snooping enabled on intermediate switches

Question 9

During multicast troubleshooting, an engineer notices that a router is not accepting MSDP Source-Active messages from a specific peer. Where should an export policy be applied to control which SA messages are sent or accepted via MSDP?

Accepted Answer

set protocols msdp peer

import . MSDP policies in Junos are applied directly under the specific MSDP peer configuration or globally under protocols msdp export/import.

Answer

set routing-options msdp-policy <policy-name>

Answer

set protocols pim msdp-import <policy-name>

Answer

set protocols bgp group msdp export <policy-name>

Question 10

An administrator troubleshooting an IGMP snooping issue on an EX Series switch notices that multicast traffic is flooding all ports in a VLAN. Which Junos command verifies the IGMP snooping status and active querier on a specific VLAN?

Accepted Answer

show igmp-snooping membership vlan vlan-name. On Juniper EX Series switches, IGMP snooping operational state and querier details per VLAN are displayed using 'show igmp-snooping membership' or 'show igmp-snooping statistics'.

Answer

show protocols igmp snooping vlan

Answer

show ethernet-switching igmp-snooping

Answer

show bridge igmp-snooping querier