JNCIP-ENT Practice Test 3 — 25 Questions

Question 1

Which Junos configuration hierarchy is used to define an EVPN routing instance of type 'evpn'?

Accepted Answer

routing-instances instance-type evpn. In Junos OS, EVPN instances are defined under 'routing-instances instance-type evpn'.

Answer

bridge-domains <name> evpn

Answer

protocols evpn

Answer

interfaces xe-0/0/0 unit 0 family evpn

Question 2

An administrator configures PoE management mode on an EX4300 switch to 'consumption'. An IP phone connects, but before booting up completely, the switch denies power. Upon investigation, you find that the switch's static power reservation table is maxed out. What is the reason for this behavior in consumption mode?

Accepted Answer

Consumption mode still requires an initial allocation based on maximum class rating until LLDP-MED or CDP successfully negotiates the lower actual consumption value.. Even in consumption mode, Junos initially allocates power based on class or a default maximum until the device negotiates its actual consumption via LLDP-MED or CDP.

Answer

Consumption mode only works with non-PoE+ devices.

Answer

Consumption mode requires manual CLI power limits for every single port.

Answer

Consumption mode disables all dynamic power allocations permanently.

Question 3

Which BGP address family must be enabled under the BGP neighbor configuration to exchange EVPN routes between PE routers?

Accepted Answer

evpn signaling (or l2vpn evpn). To exchange EVPN routing information, the 'evpn signaling' or 'l2vpn evpn' address family must be configured under the BGP protocol hierarchy and neighbor sessions.

Answer

inet-unicast

Answer

vpls-signaling

Answer

iso-unicast

Question 4

Which command is used to verify the operational state of forwarding classes and their assigned queues on a specific interface on Junos?

Accepted Answer

show class-of-service interface. The show class-of-service interface command displays operational CoS details, including queue mappings, for specified interfaces.

Answer

show route forwarding-table

Answer

show interfaces extensive

Answer

show firewall

Question 5

An operator configures a BGP routing policy to modify the Local Preference attribute. Under which BGP neighbor relationship type can Local Preference be advertised and evaluated?

Accepted Answer

Internal BGP (IBGP) peers only. Local Preference is an IBGP attribute and is exchanged only between internal BGP peers within the same autonomous system.

Answer

BGP confederation member AS boundaries only

Answer

Both EBGP and IBGP peers equally

Answer

External BGP (EBGP) peers only

Question 6

Which statement describes the function of a drop-profile in Junos CoS?

Accepted Answer

It determines when and how many packets to drop based on buffer occupancy. A drop-profile defines the packet drop probability as a function of buffer occupancy to implement RED or WRED congestion avoidance.

Answer

It maps incoming CoS bits to internal forwarding classes

Answer

It defines how traffic is shaped to a specific peak rate

Answer

It rewrites outer VLAN tags on trunk interfaces

Question 7

An engineer needs to ensure that routes received from an external BGP peer are evaluated using multipath load balancing across different next hops. By default, Junos requires several conditions to be met for multipath. Which condition is mandatory for BGP multipath to consider two paths as valid candidates?

Accepted Answer

The IGP metric to the BGP next hop must be identical for all participating paths.. To qualify for BGP multipath in Junos, multiple attributes must match by default, including AS path length, local preference, origin, MED, and the IGP metric to the respective next hops must be equal (or within an acceptable variance if configured).

Answer

The peer IP addresses must reside on the exact same subnet.

Answer

The advertising router IDs must be identical.

Answer

The cluster lists must be completely empty.

Question 8

In a BGP confederation setup, two member ASNs (65001 and 65002) belong to a larger confederation AS (65100). When routes are advertised between these two member ASs, how is the AS path attribute handled?

Accepted Answer

The member AS numbers are placed in AS_CONFED_SEQUENCE segments and are not treated as external AS hops.. Confederation member AS numbers are included in the AS_CONFED_SEQUENCE attribute and are stripped when the route exits the confederation boundary.

Answer

The confederation AS number is prepended to the front of the path, removing all member AS numbers.

Answer

The member AS numbers are completely stripped and replaced by the confederation AS number.

Answer

The route is dropped by the receiving member AS due to an inter-AS loop prevention violation.

Question 9

An engineer is troubleshooting a multicast forwarding issue where data from a specific source is not reaching receivers in a remote PIM sparse-mode domain. Which THREE operational commands and diagnostic steps should be used to verify the multicast forwarding state and RPF path on a Junos router? (Choose three)

Accepted Answer

Run 'show pim join' to inspect upstream neighbor information and verify the RPF interface for the source.. Option B is correct because 'show pim join' displays the PIM join state, including the upstream neighbor (RPF neighbor) and the incoming/RPF interface for each (S,G) or (*,G) entry, which is exactly what is needed to confirm the RPF path toward the source in a PIM sparse-mode domain. Option C is correct because 'show igmp group' verifies that receivers on the local segment have actually sent IGMP joins for the group, confirming the last-hop router has the group membership needed to build the multicast forwarding state. Option E is correct because 'show multicast route' shows the installed (S,G)/(*,G) forwarding entries along with their incoming and outgoing interfaces and packet counters, letting the engineer confirm whether traffic is being forwarded and where it may be dropping. Option A is not correct because OSPF LSA type 6 (group-membership LSA) is MOSPF-specific and is not used for RPF checks in a PIM sparse-mode domain. Option D is not correct because there is no 'show bgp summary multicast-unicast' command, and multicast RPF lookups in Junos use the unicast routing table (inet.0) or an explicit multicast RPF table, not a BGP multicast-unicast summary.

Answer

Run 'show ospf database multicast' to verify LSA type 6 propagation.

Answer

Run 'show bgp summary multicast-unicast' to verify BGP routing tables for multicast RPF checks.

Question 10

An enterprise network uses Q-in-Q tunneling over an MX Series provider network. Customer BPDUs must pass transparently across the provider core without being processed by the provider's own VSTP/MSTP instances. Which feature must be enabled on the provider switch access ports to achieve this?

Accepted Answer

Layer 2 Protocol Tunneling (L2PT). Layer 2 protocol tunneling (L2PT) or BPDU tunneling is required to encapsulate L2 control frames (like STP BPDUs) into multicast destination MAC addresses so they cross the core transparently.

Answer

MSTP region boundary enforcement

Answer

BPDU filter across all bridging domains

Answer

VLAN translation swapping on inner tags

Question 11

You need to configure a classifier that inspects the Multiprotocol Label Switching (MPLS) experimental (EXP) bits. Which classifier type must you specify?

Accepted Answer

exp. The MPLS EXP bits are classified using the exp classifier type in Junos CoS configurations.

Answer

fec

Answer

ieee-802.1

Answer

dscp

Question 12

An enterprise WAN edge router running Junos OS has a single 1 Gbps uplink. The design requires that when total egress congestion occurs, the queue carrying business-critical database replication traffic must be guaranteed a minimum of 400 Mbps, while the queue carrying guest internet traffic must never consume more than 200 Mbps even if bandwidth is idle. Which CoS configuration accomplishes this requirement?

Accepted Answer

Apply a transmit-rate of 400m to the critical queue and a shaping-rate of 200m to the guest queue in the scheduler.. Guaranteeing a minimum and enforcing a maximum are distinct scheduler behaviors. A transmit-rate provides the guaranteed minimum share during congestion, whereas a shaping-rate imposes a hard ceiling on how much a queue can transmit even when bandwidth is available. The critical queue needs the guarantee and the guest queue needs the cap, so pairing transmit-rate with shaping-rate matches the design intent.

Answer

Apply a transmit-rate of 400m to the critical queue and a transmit-rate of 200m to the guest queue in the scheduler.

Answer

Apply a shaping-rate of 400m to the critical queue and a transmit-rate of 200m to the guest queue in the scheduler.

Answer

Apply a transmit-rate of 400m with exact to the critical queue and a transmit-rate of 200m with exact to the guest queue in the scheduler.

Question 13

In Junos CoS architecture, what role does a forwarding class play?

Accepted Answer

It represents an internal queue abstraction used to group and process packets. Forwarding classes act as internal labels used by the router to group traffic into specific queues for scheduling and drop treatment.

Answer

It specifies the egress interface physical speed

Answer

It provides static IP routing table entries

Answer

It defines the physical queue index directly on the ASIC

Question 14

An enterprise network uses BGP route reflection. The design team has deployed two route reflectors in the same cluster for redundancy, with all client routers peering to both route reflectors. After a link failure, some clients receive duplicate route advertisements. Which BGP attribute is used to prevent routing loops within a route reflection cluster, and how does it function?

Accepted Answer

CLUSTER_LIST — it records the cluster IDs of route reflectors that a route has traversed, and a route reflector discards a route if its own cluster ID is already present.. The CLUSTER_LIST attribute is the mechanism that prevents routing loops when multiple route reflectors serve the same cluster. Each route reflector prepends its cluster ID to the CLUSTER_LIST when reflecting a route. If a route reflector receives a route that already contains its own cluster ID in the CLUSTER_LIST, it discards the route. This ensures that a route cannot loop back to a route reflector that has already processed it, even if multiple route reflectors exist in the same cluster.

Answer

ORIGINATOR_ID — it identifies the originating router, and a route reflector discards a route if it sees its own router ID as the originator.

Answer

AS_PATH — it records the autonomous systems a route has traversed, and a route reflector discards a route if its own AS number appears in the path.

Answer

MULTI_EXIT_DISC (MED) — it carries metric information and is used to prevent loops by comparing metrics across multiple route reflectors.

Question 15

You are deploying a Juniper EX Series switch as an access layer device in a campus network. The uplink port ge-0/0/1 connects to a distribution switch and is expected to carry traffic for VLANs 10, 20, and 30. You want to prevent the access switch from becoming the root bridge for any of these VLANs and ensure that the uplink is preferred for forwarding. Which configuration should you apply on the access switch?

Accepted Answer

Set the bridge priority to 61440 on the access switch and configure the uplink port with a lower path cost.. To prevent the access switch from becoming the root bridge, a high bridge priority such as 61440 is appropriate. To ensure the uplink is preferred for forwarding, a lower path cost on that port is necessary. Together, these settings control both root bridge election and path selection, aligning with best practices for access layer switches in a campus network.

Answer

Enable RSTP on the access switch and set the uplink port as an edge port to prioritize forwarding.

Answer

Set the bridge priority to 4096 on the access switch and configure the uplink port as the root port using the root-port command.

Answer

Configure the uplink port with a higher path cost and set the bridge priority to 61440 on the access switch.

Question 16

You are configuring a Juniper EX Series switch to support a Layer 2 network with multiple VLANs. You want to use RSTP for faster convergence but need to ensure that each VLAN has its own spanning-tree instance. Which feature should you enable?

Accepted Answer

VSTP. VSTP is the Juniper implementation that runs RSTP per VLAN, providing a separate spanning-tree instance for each VLAN. This meets the requirement of per-VLAN instances with rapid convergence. RSTP and STP use a single instance for all VLANs, and MSTP maps multiple VLANs to a single instance, so they do not provide one instance per VLAN. VSTP is the appropriate feature for this design.

Answer

STP

Answer

RSTP

Answer

MSTP

Question 17

You are deploying a Junos EX Series switch in a campus network. Voice packets arrive untagged from IP phones on access ports, while a trunk uplink carries traffic already marked with DSCP values from the core. You need to ensure that all ingress traffic on the uplink is classified into forwarding classes based solely on the existing DSCP bits without inspecting Layer 3 or Layer 4 headers. Which classifier type should you apply to the uplink interface?

Accepted Answer

Behavior aggregate classifier. Because the incoming packets on the uplink already carry DSCP markings from the core and the goal is to classify them without deeper header inspection, a behavior aggregate classifier is the correct mechanism. BA classifiers map a single CoS field such as DSCP directly to a forwarding class and loss priority, providing efficient, marking-based classification at ingress.

Answer

Fixed classifier

Answer

Multifield classifier

Answer

EXP classifier

Question 18

Which TWO commands are used to troubleshoot OSPF issues on Junos devices? (Choose two)

Accepted Answer

show ospf neighbor. Operational commands like 'show ospf neighbor' and 'show ospf database' are standard for troubleshooting OSPF adjacencies and LSDB status.

Answer

show ip ospf interface

Answer

show protocols ospf status

Answer

show route ospf-table

Question 19

A network engineer notices that on a Junos EX Series switch, the voice queue is configured with strict-high priority, but during periods of congestion, data traffic is being dropped while voice traffic is unaffected. The engineer wants to ensure that voice traffic is not only prioritized but also limited so it cannot consume all interface bandwidth. Which scheduler property should be added to the voice queue to cap its maximum transmission rate?

Accepted Answer

shaping-rate. A strict-high priority queue can consume all available bandwidth during congestion, starving lower-priority queues. To prevent this while preserving priority servicing, the shaping-rate property must be configured on the voice queue to enforce a maximum transmission rate. This caps the voice queue's consumption and protects other traffic.

Answer

transmit-rate

Answer

buffer-size

Answer

excess-rate

Question 20

You are deploying a Junos device where a single physical interface carries both a latency-sensitive multicast video stream and best-effort file transfers. You must ensure that the video traffic is transmitted with the lowest possible per-hop latency and jitter, even when the best-effort queue is congested, without starving the other queues. Which CoS feature should you configure on the egress interface to meet this requirement?

Accepted Answer

A strict-high priority scheduler applied to the video forwarding class queue. Strict-high priority scheduling is the only Junos scheduler property that guarantees a queue is serviced ahead of all others when packets are present, which is exactly what latency-sensitive multicast video requires under congestion. Weighted scheduling, low-priority scheduling, and policing all address bandwidth allocation or rate limiting rather than strict preferential transmit ordering, so they cannot provide the lowest per-hop latency and jitter.

Answer

A low-priority scheduler with a large buffer size on the video queue

Answer

A weighted round-robin scheduler with a high transmit-rate on the video queue

Answer

A rate-limited policer applied to the video forwarding class