JNCIP-ENT Practice Test 14 — 15 Questions

Question 1

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 2

When configuring advanced VLAN mapping on a Juniper MX Series router using flexible VLAN tagging, which term describes the action of replacing an incoming inner VLAN tag with a new tag before forwarding into the provider core?

Accepted Answer

VLAN swap. VLAN translation or swapping replaces the incoming tag with a mapped tag.

Answer

VLAN stripping

Answer

VLAN push

Answer

VLAN pop

Question 3

An administrator implements BGP entropy labels and path load balancing on a Junos routing platform. During packet forwarding for a BGP-learned IPv4 prefix with multiple equal-cost paths, how does Junos determine the output interface when hash-based load balancing is active?

Accepted Answer

Hashing selected packet header fields to compute an index into the set of resolved BGP next hops.. Junos hashes packet header fields (such as source/destination IP, ports, and optional hash keys or entropy labels) to select a specific path from the available BGP multipaths.

Answer

Using the lowest MED value among the multipath entries for every packet transmission.

Answer

Consulting the BGP Route Reflector cluster list to determine the optimal egress port.

Answer

Round-robin packet scheduling across all available BGP next hops regardless of flow headers.

Question 4

You are configuring an OSPF NSSA and want to suppress the translation of Type-7 LSAs into Type-5 LSAs on one of the ABRs because another ABR is already performing the translation. Which statement is used?

Accepted Answer

set protocols ospf area 0.0.0.2 nssa no-translate. To prevent an NSSA ABR from translating Type-7 LSAs into Type-5 LSAs, you configure the 'no-translate' option under the nssa statement.

Answer

set protocols ospf area 0.0.0.2 nssa suppress-translation

Answer

set protocols ospf area 0.0.0.2 nssa no-type-5-conversion

Answer

set protocols ospf area 0.0.0.2 nssa translator-role never

Question 5

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 6

Which THREE methods are valid for marking packet headers using CoS rewrite rules in Junos? (Choose three)

Accepted Answer

exp. In Junos CoS rewrite rules, the valid header fields you can rewrite are the EXP bits (for MPLS), IEEE 802.1p (for Layer 2 CoS), and DSCP (for IP ToS). Option A (exp) is correct because MPLS EXP bits are rewritten via the exp rewrite rule. Option B (ieee-802.1) is correct because 802.1p priority bits in VLAN tags are rewritten via the ieee-802.1 rewrite rule. Option C (dscp) is correct because IP DSCP values are rewritten via the dscp rewrite rule. Options D (vlan-id) and E (mpls-ttl) are not valid rewrite-rule match/rewrite fields; vlan-id is a VLAN identifier, not a CoS marking, and MPLS TTL is a forwarding/hop-limit field, not a CoS rewrite target.

Answer

vlan-id

Answer

mpls-ttl

Question 7

You need to ensure that delay-sensitive voice traffic is serviced before all other queues on an egress interface. Which scheduler property should you configure for the voice forwarding class?

Accepted Answer

priority high. In Junos, priority high or priority low is used to designate strict priority queuing for a forwarding class in a scheduler.

Answer

buffer-size

Answer

transmit-rate

Answer

drop-profile

Question 8

An engineer is configuring BGP route resolution and next-hop tracking in Junos. Which TWO circumstances will cause a BGP next hop to be marked as unresolved or unusable? (Choose two)

Accepted Answer

The resolving route in the IGP routing table points to a discard or reject dead-end route.. BGP next hops become unusable if the resolving route in the IGP table is missing, points to a discard/reject route, or lacks reachability.

Answer

The BGP next-hop IP address matches a directly connected interface subnet on the router.

Answer

The BGP neighbor session is established over a loopback interface using multihop.

Answer

The resolving route has an active loop-free alternate backup path installed.

Question 9

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 10

You are integrating an EVPN-VXLAN fabric with an existing MPLS L3VPN backbone using a data center gateway. Which route type allows seamless translation and communication of prefix routes between the EVPN instance and the IP-VRF MPLS VPN backbone?

Accepted Answer

Route Type 5. EVPN Route Type 5 (IP Prefix Route) permits the advertising of IP prefixes that can be easily imported into IP-VRFs, bridging EVPN and classical MPLS L3VPN domains.

Answer

Route Type 3

Answer

Route Type 1

Answer

Route Type 2

Question 11

When configuring centralized gateway or distributed gateway routing models in an EVPN-VXLAN environment, how does a distributed gateway using Integrated Routing and Bridging (IRB) interfaces operate regarding default gateway functionality?

Accepted Answer

All leaf nodes act as default gateways using the same virtual MAC and IP address, terminating traffic locally.. In a distributed gateway model, every leaf/VTEP acts as the default gateway for its directly attached subnets, using anycast MAC and IP addresses so hosts can send traffic to their local VTEP regardless of which leaf they connect to.

Answer

Routing is disabled on leaf nodes, requiring all packets to be tunneled to spine nodes for L3 lookup.

Answer

A single designated MX core router handles all inter-subnet routing via centralized IRB interfaces.

Answer

Hosts must run VRRP between leaf nodes to dynamically elect a single active gateway.

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

An engineer is troubleshooting a large-scale enterprise network with multiple MSTP regions connected by a legacy RSTP region. How do boundary switches running MSTP interact with RSTP switches on shared segments?

Accepted Answer

MSTP boundary ports detect RSTP BPDUs and operate in RSTP compatibility mode on that specific port.. MSTP bridge ports connected to RSTP regions automatically downgrade their communication mode to interoperate with RSTP/STP BPDUs.

Answer

MSTP boundary ports drop all RSTP BPDUs and treat the link as a point-to-point blocked topology.

Answer

The entire MSTP region converts its configuration digest to match the RSTP region's default region name.

Answer

MSTP isolates the RSTP region into a separate MSTI instance automatically.

Question 14

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?

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 15

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.. Option B is correct because IGMP snooping lets the switch listen to IGMP Membership Reports and Leave messages, so it can prune multicast streams from switch links where no receivers exist, thereby conserving bandwidth on those links. Option E is correct because, by default, a Layer 2 switch floods multicast frames out every port in the VLAN; IGMP snooping builds a per-VLAN multicast forwarding table and forwards each group's traffic only to ports that have joined that group via IGMP, preventing unnecessary flooding. Option A is wrong because the PIM Rendezvous Point is a Layer 3 multicast routing function, not something IGMP snooping provides on a switch. Option C is wrong because IGMP snooping does not perform any IPv4-to-IPv6 multicast address translation. Option D is wrong because IGMP snooping operates at Layer 2 and does not replace PIM sparse-mode, which is required for multicast routing between subnets on Layer 3 devices.

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.