JNCIP-ENT Practice Exam 4 — 20 Questions

Question 1

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 2

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 3

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 4

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 5

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 6

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 7

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 8

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 9

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 10

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

Question 11

Which TWO statements describe the function and operation of a PIM Bootstrap Router (BSR)? (Choose two)

Accepted Answer

The BSR collects Candidate-RP messages and periodically distributes the RP-set to all PIM routers.. The BSR collects Candidate-RP advertisements and distributes the RP-set to all routers in the domain via bootstrap messages.

Answer

The BSR acts as the data encapsulation point for multicast sources.

Answer

The BSR forwards multicast data packets directly to receivers.

Answer

The BSR is required to establish MSDP sessions between autonomous systems.

Question 12

You are deploying an EVPN-VXLAN fabric with a pair of Juniper EX Series switches acting as leaf devices for a dual-homed server. The server is connected to both leaf switches using a LAG with LACP, and you want to achieve All-Active multihoming so that both leaf switches can forward traffic to and from the server simultaneously. Which statement correctly describes the role of the Designated Forwarder (DF) in this scenario?

Accepted Answer

The DF election ensures that only one of the two leaf switches forwards broadcast, unknown unicast, and multicast (BUM) traffic to the server, while both can forward known unicast traffic.. In EVPN All-Active multihoming, the Designated Forwarder election per Ethernet segment ensures that only one PE forwards BUM traffic to the multihomed device, preventing duplicate packets. However, all PEs in the Ethernet segment can forward known unicast traffic, enabling load balancing and active-active connectivity. This is a key advantage of All-Active multihoming over Single-Active, where only one PE forwards all traffic.

Answer

The DF election designates one leaf switch to handle all traffic for the server, while the other remains on standby until a failure occurs.

Answer

The DF election is not required for All-Active multihoming because both leaf switches can forward BUM traffic without causing duplicates.

Answer

The DF election ensures that only one leaf switch is active for all traffic types, including known unicast, to the server.

Question 13

You are deploying an EVPN-VXLAN fabric on Juniper MX Series routers. Host A is attached to a leaf device and its MAC address is learned locally. You need to ensure that this MAC is advertised to all other leaf devices in the same EVPN instance so they can forward traffic to Host A without flooding. Which EVPN route type should you verify is being generated and advertised?

Accepted Answer

Type 2 - MAC/IP Advertisement route. Type 2 routes are the standard EVPN mechanism for advertising MAC and IP reachability. When a leaf learns a local MAC, it generates a Type 2 route including the MAC, the VXLAN VNI, and the next-hop. This route is propagated via BGP EVPN to other leaf devices, which then program their forwarding tables to send traffic directly to the originating leaf. This eliminates unknown unicast flooding for known hosts.

Answer

Type 1 - Ethernet Auto-Discovery route

Answer

Type 3 - Inclusive Multicast Ethernet Tag route

Answer

Type 4 - Ethernet Segment route

Question 14

You manage a Juniper Networks enterprise network using OSPF. Router R1 and Router R2 are connected via a point-to-point link. R1 is configured with the interface ge-0/0/0.0 in area 0 with a hello interval of 10 seconds and a dead interval of 40 seconds. R2 has the same interface in area 0 but with a hello interval of 30 seconds and a dead interval of 120 seconds. After configuration, the OSPF adjacency does not form. Which action will resolve the issue?

Accepted Answer

Change the hello interval on R1 to 30 seconds and the dead interval to 120 seconds.. OSPF requires that the hello and dead intervals match on both routers for an adjacency to form. In this scenario, R1 has hello 10 and dead 40, while R2 has hello 30 and dead 120. Changing R1's timers to match R2's will allow the adjacency to establish. The other options would not resolve the timer mismatch and could introduce additional issues.

Answer

Change the OSPF router ID on R1 to be higher than R2's router ID.

Answer

Change the network type on R1 to non-broadcast.

Answer

Change the OSPF area on R1 to area 1.

Question 15

You are troubleshooting an EVPN-VXLAN fabric where a host behind Leaf 1 is unable to communicate with a host behind Leaf 2, even though both hosts are in the same VLAN and EVPN instance. You verify that Type 2 routes are being exchanged, but traffic is not forwarded. You suspect an issue with the VXLAN tunnel. Which Junos command would you use to check the status of the VXLAN tunnel interface and its associated VTEP?

Accepted Answer

show interfaces vtep. The 'show interfaces vtep' command is the primary tool to verify the operational status of the VXLAN tunnel endpoint interface on Junos devices. It shows whether the VTEP is up, its encapsulation type, and associated VNIs. If the VTEP is down, VXLAN tunnels cannot be established, and traffic cannot be encapsulated and forwarded, even if EVPN routes are correctly exchanged. This command directly addresses the suspected data plane issue.

Answer

show configuration protocols evpn

Answer

show route table bgp.evpn.0

Answer

show ethernet-switching table

Question 16

A Junos router is the last-hop router for receivers in VLAN 100. The receivers use IGMPv3 and request group 239.5.5.5 from source 10.10.10.10 only. The router has a PIM sparse-mode shared tree (*,G) toward the RP, but traffic from 10.10.10.10 is not being delivered to the receivers. The unicast route to 10.10.10.10 points out a different interface than the one toward the RP. Which action resolves the problem?

Accepted Answer

Ensure PIM is enabled on the interface toward 10.10.10.10 so the router can build the (S,G) tree.. When a receiver requests a specific source and group, the last-hop router must create (S,G) state and send a PIM join toward the source using the unicast route to the source address. That route can differ from the path toward the rendezvous point. If PIM is not enabled on the outgoing interface toward the source, the join cannot be sent and traffic is never forwarded, so PIM must be enabled on that interface.

Answer

Add a static IGMP group membership for 239.5.5.5 on the VLAN 100 interface.

Answer

Configure an RP for the group so the shared tree can be used for delivery.

Answer

Increase the IGMP query interval on VLAN 100 so the receiver reports are refreshed more often.

Question 17

You are troubleshooting an OSPF network where a Juniper router is not installing a particular OSPF route into its routing table. The route is present in the OSPF link-state database as an external LSA, but it is not in the inet.0 table. You have verified that the route is not filtered by any policy. What is the most likely cause?

Accepted Answer

The external LSA has a forwarding address that is unreachable.. The forwarding address in an external LSA must be reachable for OSPF to install the route. If it is not, the route remains in the LSDB but is not used. This is a common troubleshooting point for OSPF external routes.

Answer

The OSPF route preference is lower than another protocol's route.

Answer

The OSPF area is a stub area, which blocks external LSAs.

Answer

The OSPF router ID is not configured.

Question 18

You are configuring captive portal on an EX Series switch. Users must be redirected to an external web server for authentication. You have configured the captive portal profile with the redirect URL. However, users are not being redirected and can access the Internet without authentication. Which configuration issue is most likely?

Accepted Answer

The captive portal profile is not applied to the interface.. Captive portal requires the profile to be applied to the interface. Without this, the switch does not intercept HTTP traffic and redirect users to the authentication page. The redirect URL alone is insufficient; the profile must be bound to the interface to activate the feature.

Answer

The 'authentication-order' is set to 'radius' instead of ' captive-portal'.

Answer

The 'interface-mode' is set to trunk instead of access.

Answer

The 'redirect-url' is not configured under the captive portal profile.

Question 19

You are configuring an EX Series switch to support IP phones that use LLDP-MED for network policy. Which two statements are true about LLDP-MED network policy TLVs? (Choose two.)

Accepted Answer

They can specify the Layer 2 priority and DSCP values for QoS.. LLDP-MED network policy TLVs are sent by the switch to the phone and include VLAN ID, Layer 2 priority, and DSCP values. These parameters allow the phone to configure its VLAN and QoS settings automatically. They are not sent by the phone, can be used for multiple application types, and require LLDP to be enabled.

Answer

They are sent by the phone to the switch to request VLAN assignment.

Answer

They are only used for voice applications and not for other media types.

Answer

They require LLDP to be disabled to function properly.

Question 20

Which Junos configuration hierarchy is used to define a BGP peer group to simplify neighbor configurations?

Accepted Answer

protocols bgp group <group-name>. BGP peer groups and neighbor settings are configured under the 'protocols bgp group' hierarchy in Junos.

Answer

routing-options autonomous-system

Answer

interfaces <interface-name> unit 0 family inet bgp

Answer

policy-options community