JNCIP-ENT Practice Exam 3 — 20 Questions

Question 1

What is the default number of forwarding classes available on Juniper MX Series routers equipped with Modular Port Concentrators (MPCs)?

Accepted Answer

64. Junos supports up to 64 forwarding classes on modern MPC-based hardware platforms, though default configurations typically use a subset.

Answer

4

Answer

8

Answer

16

Question 2

What is the primary function of a behavior aggregate (BA) classifier in Junos CoS?

Accepted Answer

It classifies packets based exclusively on header CoS bits such as DSCP or EXP. A Behavior Aggregate (BA) classifier classifies packets based solely on the CoS bits in the packet header (such as DSCP, EXP, or IEEE 802.1p).

Answer

It drops packets exceeding a predefined bandwidth rate

Answer

It rewrites VLAN tags on egress interfaces

Answer

It classifies packets based on Layer 4 port numbers and source IP addresses

Question 3

Which command displays the configured scheduler maps and their association with forwarding classes on a Junos device?

Accepted Answer

show class-of-service scheduler-map. The show class-of-service scheduler-map command displays details of scheduler maps and queue associations.

Answer

show class-of-service queue

Answer

show class-of-service forwarding-class

Answer

show configuration class-of-service schedulers

Question 4

Which TWO statements are correct regarding the behavior of policers in Junos? (Choose two)

Accepted Answer

Policers can mark the loss priority of exceeding packets. Policers can drop traffic or mark loss priority, and they operate based on token bucket algorithms.

Answer

Policers buffer exceeding packets in temporal memory queues until transmission capacity opens

Answer

Policers are always applied to egress interfaces only

Answer

Policers guarantee a minimum bandwidth allocation for best-effort traffic

Question 5

Which THREE components are required to fully configure a custom Class of Service scheme on an MX Series router? (Choose three)

Accepted Answer

schedulers. Implementing custom CoS requires forwarding classes, classifiers, and schedulers.

Answer

dynamic-profiles

Answer

bgp-routes

Question 6

You want to configure voice VLAN functionality on a Juniper EX switch so that IP phones automatically place voice traffic into VLAN 50 while passing PC data through unchanged. Which feature should you configure?

Accepted Answer

LLDP-MED with voice VLAN assignment. Voice VLAN feature on EX switches automatically assigns voice traffic from known MAC OUIs to the designated voice VLAN.

Answer

MAC-based RADIUS dynamic VLAN assignment

Answer

Layer 2 protocol tunneling (L2PT)

Answer

IEEE 802.1X supplicant authentication

Question 7

You are configuring Ethernet switching on an EX4300 switch and need to implement storm control to prevent broadcast, multicast, and unknown unicast traffic from overwhelming access links. Where is storm-control applied in the Junos configuration hierarchy?

Accepted Answer

set interfaces ge-0/0/1 unit 0 family ethernet-switching storm-control. Storm control is applied under 'interfaces <interface-name> unit 0 family ethernet-switching storm-control'.

Answer

set vlans default storm-control

Answer

set protocols l2-learning storm-control interface ge-0/0/1

Answer

set forwarding-options storm-control interface ge-0/0/1

Question 8

Which TWO actions can be triggered when a MAC address limit is exceeded on a Juniper switch interface configured with MAC limiting? (Choose two)

Accepted Answer

drop. Configurable actions on MAC limit violation include drop and log, or drop and shutdown (disable) the interface.

Answer

quarantine

Answer

reboot

Answer

isolate-vlan

Question 9

When configuring advanced Layer 2 tunneling (Q-in-Q) on Juniper EX Series switches, which THREE statements are correct regarding VLAN stacking behavior and limitations? (Choose three)

Accepted Answer

MTU sizes across the core must be adjusted to account for the extra 4 bytes of the added outer VLAN tag.. QinQ on Juniper EX switches involves specific encapsulation requirements like flexible-ethernet-services, stacking VLAN tags on ingress and popping on egress, and preserving inner customer VLAN tags transparently.

Answer

Layer 2 Protocol Tunneling (L2PT) is automatically enabled for all protocols without additional configuration when QinQ is active.

Answer

QinQ tunneling requires standard access mode encapsulation on all core-facing uplink ports.

Question 10

Which TWO parameters can be configured within a Junos scheduler definition? (Choose two)

Accepted Answer

transmit-rate. Schedulers include parameters such as transmit-rate, buffer-size, priority, and drop-profile-map.

Answer

rewrite-rule

Answer

bandwidth-limit

Answer

policer-action

Question 11

Which TWO statements are correct regarding hierarchical scheduling (H-QoS) on Juniper MX Series routers? (Choose two)

Accepted Answer

Subscriber management frameworks often utilize hierarchical scheduler maps. Hierarchical schedulers allow multi-level bandwidth allocation and tenant sub-rate shaping.

Answer

H-QoS eliminates the need for physical interface drop profiles

Answer

H-QoS is configured exclusively under the system routing-options hierarchy

Answer

H-QoS requires disabling all hardware-based forwarding ASICs

Question 12

You are configuring VSTP (VLAN Spanning Tree Protocol) on Juniper EX switches to interoperate with legacy third-party switches running PVST+. Which operational command allows you to verify the VSTP bridge identifier and root bridge status per VLAN?

Accepted Answer

show vstp vlan. The command 'show vstp vlan' displays the VSTP state, root bridge, and port roles for each VLAN.

Answer

show ethernet-switching vstp

Answer

show spanning-tree vlan detail

Answer

show bridge vstp-status

Question 13

An administrator needs to filter Type-3 LSAs entering an OSPF stub area on a Junos routing device. Which statement under the area hierarchy is required?

Accepted Answer

set protocols ospf area 0.0.0.2 area-range 192.168.1.0/24 restrict. In Junos OS, you can filter inbound Type-3 LSAs into a stub or NSSA area using the 'area-range' command with the 'restrict' or 'hidden' parameter, or using an import policy at the area level, but specifically for summarization and blocking, the area-range statement with 'restrict' prevents the LSA from being advertised.

Answer

set protocols ospf area 0.0.0.2 type-3-lsa-block

Answer

set protocols ospf area 0.0.0.2 stub lsa-filter block-type-3

Answer

set protocols ospf area 0.0.0.2 filter type-3-lsa

Question 14

You need to modify the priority of a Junos OSPF interface to ensure it becomes the designated router (DR). Which command accomplishes this?

Accepted Answer

set protocols ospf area 0.0.0.0 interface xe-0/0/0.0 priority 200. OSPF interface priority is configured under the interface level within protocols ospf using the 'priority' command.

Answer

set interfaces xe-0/0/0.0 ospf-priority 200

Answer

set protocols ospf priority 200 interface xe-0/0/0.0

Answer

set protocols ospf area 0.0.0.0 interface xe-0/0/0.0 dr-priority 200

Question 15

You want to tune OSPF convergence by reducing the hello and dead intervals on a point-to-point interface. Which configuration is valid?

Accepted Answer

set protocols ospf area 0.0.0.0 interface xe-0/0/0.1 hello-interval 1. OSPF interface timers such as hello-interval and dead-interval are configured directly under the interface hierarchy within protocols ospf.

Answer

set protocols ospf area 0.0.0.0 timers hello-interval 1

Answer

set interfaces xe-0/0/0.1 ospf hello-interval 1

Answer

set protocols ospf hello-interval 1 dead-interval 4

Question 16

When configuring EVPN multi-homing in all-active mode, which THREE key components or concepts must be properly established across the PE routers? (Choose three)

Accepted Answer

A Designated Forwarder (DF) election mechanism using Type-4 routes to determine who forwards BUM traffic.. EVPN all-active multi-homing requires a consistent Ethernet Segment Identifier (ESI) across participating PEs, an active Designated Forwarder election (governed by Type-4 routes), and split-horizon filtering to prevent traffic loops.

Answer

Enabling Spanning Tree Protocol root bridge on all leaf nodes.

Answer

Configuring OSPF as the underlay routing protocol for EVPN signaling.

Question 17

Which TWO actions can be performed by an OSPF routing policy export filter when redistributing routes into OSPF? (Choose two)

Accepted Answer

Modify the OSPF route metric using the metric action.. Routing policies when exporting into OSPF can set metric types (Type 1 or Type 2) and modify route metrics. They cannot directly change area ID during redistribution without area design changes.

Answer

Change the OSPF hello timer interval via routing policy.

Answer

Alter the OSPF router ID of neighboring routers.

Answer

Change the OSPF area ID of external routes dynamically.

Question 18

An engineer configures an EVPN instance with multiple bridge domains. Each bridge domain requires a unique VNI. Where are the VNI values mapped to their respective bridge domains in Junos OS?

Accepted Answer

Under routing-instances bridge-domains vni . In Junos OS, VNI values are mapped under the 'bridge-domains' hierarchy using the 'vni ' statement.

Answer

Under protocols bgp neighbor configuration

Answer

Under interfaces loopback unit 0 vni

Answer

Under policy-options community definition

Question 19

You are configuring MAC limiting on an EX Series switch interface to restrict the maximum number of learned MAC addresses to 10. What happens when the 11th unique MAC address attempts to communicate through the interface?

Accepted Answer

The switch drops packets from the new MAC address and optionally logs or generates an SNMP trap.. By default, MAC limit drop or log actions occur. The standard configurable action when a limit is exceeded includes dropping the packet or shutting down the port.

Answer

The switch immediately reboots the line card to protect the control plane.

Answer

The switch forwards the frame and clears the oldest learned MAC entry from the forwarding table.

Answer

The switch dynamically converts the port into a routed Layer 3 interface.

Question 20

An enterprise network engineer is designing a redundant Layer 2 topology with MSTP across Juniper EX switches. Two switches have identical bridge priorities and MAC addresses that result in a tie for regional root. How does MSTP deterministically break the tie to select the regional root bridge?

Accepted Answer

The switch with the numerically lowest MAC address is selected as the root bridge.. Spanning tree tie-breaking checks the bridge priority first, and if tied, compares the lowest MAC address of the switches.

Answer

The switch with the highest interface count operational status wins.

Answer

The switch with the higher serial number stored in EEPROM is chosen.

Answer

MSTP triggers a randomized tie-breaker algorithm using the system uptime.