JNCIP-ENT Class OF Service Practice Test 2 — 15 Questions

Question 1

You are designing a CoS configuration on a Junos MX Series router for an egress interface that carries voice, video, and best-effort data. You need to ensure that delay-sensitive voice traffic receives strict priority treatment, while video and data share the remaining bandwidth according to configured weights. Which TWO scheduler configuration elements are required to achieve this design? (Choose two.)

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Assign priority strict-high to the voice queue.. To give voice strict priority, the voice queue must be configured with priority strict-high. To make video and data share the remaining bandwidth by weight, excess-rate values must be applied to those queues, defining their proportional share after voice is serviced. Together these elements fulfill the design requirements.

Answer

Assign a shaping-rate to the data queue equal to the interface bandwidth.

Answer

Assign a large buffer-size percentage to the best-effort data queue.

Answer

Assign priority strict-high to both the video and voice queues.

Question 2

You are designing CoS for a Junos EX Series switch that carries both latency-sensitive voice and best-effort data. You plan to use a scheduler map on the uplink interface. Which TWO statements correctly describe scheduler behavior in this scenario? (Choose two.)

Accepted Answer

A queue configured with a transmit-rate of percent 20 is guaranteed at least 20 percent of the interface bandwidth.. Priority ordering in Junos places strict-high above high, so voice on a strict-high queue is serviced first. A percentage transmit-rate reserves that share of interface bandwidth for the queue, guaranteeing at least that amount when the interface is operational and the map is valid.

Answer

A queue configured with low priority is serviced before a queue configured with high priority when the low-priority queue is backlogged.

Answer

A queue configured with a transmit-rate of remainder receives all bandwidth not allocated to other queues.

Answer

A scheduler map applied to an interface replaces the default scheduler map for all queues on that interface.

Question 3

When configuring a hierarchical scheduler map on an MX Series router, what is the primary purpose of the aggregate level shaping?

Accepted Answer

To limit the total traffic across all queues associated with the scheduler map. Aggregate level shaping controls the total bandwidth allocated to a group of queues or sub-interfaces, ensuring overall traffic limits are respected.

Answer

To dynamically assign forwarding classes based on IP headers

Answer

To ensure absolute priority for best-effort traffic

Answer

To rewrite CoS bits on egress frames

Question 4

Which standard Junos forwarding class is reserved for control plane traffic such as routing protocols and management traffic?

Accepted Answer

network-control. In Junos, the network-control forwarding class is reserved for control plane traffic to ensure it receives priority handling.

Answer

expedited-forwarding

Answer

assured-forwarding

Answer

best-effort

Question 5

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 6

You want to apply a rewrite rule on an outgoing interface to remark the DSCP bits of packets leaving your Juniper router. Where must this rewrite rule be applied within the CoS hierarchy?

Accepted Answer

[edit class-of-service interfaces]. Rewrite rules in Junos are applied on egress interfaces under the interfaces statement within the class-of-service configuration hierarchy.

Answer

[edit firewall]

Answer

[edit routing-options]

Answer

[edit class-of-service classifiers]

Question 7

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 8

Which configuration stanza is used to define custom forwarding classes in Junos?

Accepted Answer

[edit class-of-service forwarding-classes]. Custom forwarding classes are defined under the [edit class-of-service forwarding-classes] hierarchy.

Answer

[edit class-of-service drop-profiles]

Answer

[edit class-of-service classifiers]

Answer

[edit class-of-service schedulers]

Question 9

You have configured a custom scheduler map, but traffic in the best-effort queue is being starved during periods of heavy congestion. Which scheduler parameter should you adjust to guarantee a minimum bandwidth for this queue?

Accepted Answer

transmit-rate. The transmit-rate parameter in a scheduler definition guarantees a minimum bandwidth allocation for a queue even during congestion.

Answer

drop-profile-map

Answer

buffer-size temporal

Answer

priority high

Question 10

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 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

When applying a rewrite rule on an interface, you notice that packets are being remarked incorrectly. You realize that both a DSCP rewrite rule and an IEEE 802.1p rewrite rule are configured on the same physical interface. What is the rule regarding multiple rewrite rules on a single interface in Junos?

Accepted Answer

Different rewrite rule types (such as DSCP and ieee-802.1) can be applied simultaneously on the same logical interface. Junos allows only one rewrite rule per packet header type (e.g., one DSCP, one 802.1p) per logical interface, but you can have different header types applied simultaneously if they map to different packet layers.

Answer

Applying multiple rewrite rules causes an automatic system kernel crash

Answer

Only one rewrite rule total can be applied per logical interface regardless of type

Answer

Only Layer 2 rewrite rules are permitted on trunk ports

Question 13

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 14

An engineer configures a two-color policer on an MX router. What are the two states or outcomes for evaluated packets in a standard two-color policer?

Accepted Answer

Green and Red. A two-color policer evaluates packets as either conforming (within the rate limit) or non-conforming (exceeding the rate limit).

Answer

In-profile and Out-of-profile only with temporal buffers

Answer

Green, Yellow, and Red

Answer

Discard and Forward without loss priority marking

Question 15

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