350-501 Practice Test 25 — 15 Questions

Question 1

Which TWO statements about MPLS label operations are correct? (Choose two.)

Accepted Answer

Label swapping is performed at every transit LSR.. Penultimate Hop Popping (PHP) removes the label before the final hop, and the ingress LSR pushes the initial label.

Answer

The ingress LSR performs a swap operation.

Answer

The egress LSR always performs a pop operation.

Answer

Label popping always happens at the penultimate hop.

Question 2

In EVPN multi-homing with all-active mode, which mechanism is used to elect a designated forwarder (DF) for broadcast, unknown unicast, and multicast (BUM) traffic on a given Ethernet segment?

Accepted Answer

DF election via ESI label and route type 4. The DF election is performed using a deterministic algorithm based on the ESI and the list of PEs, with the lowest IP address becoming DF.

Answer

Load balancing via MLAG

Answer

ES-IS protocol

Answer

MSTP

Question 3

What is the purpose of the SRGB (Segment Routing Global Block) in SR-MPLS?

Accepted Answer

It defines a contiguous block of labels used for global SIDs such as Node SIDs.. The SRGB defines a range of labels reserved for global segment routing SIDs (e.g., Node SIDs). It ensures that the same label value represents the same prefix across the domain, avoiding label conflicts.

Answer

It defines the range of labels for Adjacency SIDs.

Answer

It is used to reserve labels for RSVP-TE tunnels.

Answer

It is the set of labels allowed for MPLS VPNs.

Question 4

Which MPLS TE mechanism provides link protection by pre-establishing a backup LSP that bypasses a specific link, activated when the link fails?

Accepted Answer

Bypass tunnel. RSVP-TE Fast Reroute uses bypass tunnels to protect links, providing local repair upon failure.

Answer

LDP FRR

Answer

Detour tunnel

Answer

TE backup path

Question 5

Which THREE DSCP values are part of the Assured Forwarding (AF) class 4? (Select three.)

Accepted Answer

DSCP 34. AF4 has three drop probabilities: low (AF41 = DSCP 34), medium (AF42 = DSCP 36), high (AF43 = DSCP 38).

Answer

DSCP 40

Answer

DSCP 46

Question 6

An SP engineer is configuring QoS on a PE router for MPLS traffic. The core network uses MPLS EXP bits for QoS. Which TWO methods can be used to set MPLS EXP bits based on IP DSCP? (Select two.)

Accepted Answer

Use a policy-map with 'set mpls experimental' command.. On Cisco routers, you can use 'set mpls experimental imposition' to set EXP on the imposed label, or use a QoS policy with 'set mpls experimental' in a policy-map.

Answer

Configure 'mpls qos enforce' on the interface.

Answer

Configure 'mpls ip' to automatically copy DSCP to EXP.

Answer

Apply 'qos-group' to DSCP mapping.

Question 7

Which component in MQC is used to classify traffic based on match criteria?

Accepted Answer

Class-map. In MQC, a class-map defines the match criteria to classify traffic.

Answer

Service-policy

Answer

Policy-map

Answer

Access-list

Question 8

An SP is designing MQC policies. Which THREE statements about MQC are true? (Choose three.)

Accepted Answer

MQC uses a three-step process: define class-map, policy-map, and apply service-policy. MQC uses class-map, policy-map, and service-policy; class-map can match multiple criteria; policy-map defines actions.

Answer

In a policy-map, the class class-default is optional

Answer

A policy-map can contain only one class

Question 9

An SP uses NSO for service orchestration. A new service requires YANG data validation to ensure that the 'bandwidth' leaf does not exceed 10000 kbps when the 'service-type' is 'premium'. Which YANG statement is appropriate?

Accepted Answer

must '. <= 10000' { error-message 'Bandwidth too high'; }. A 'must' expression in YANG provides a XPath condition that must evaluate to true for the data to be valid.

Answer

when '. <= 10000'

Answer

leafref bandwidth { path '../bandwidth-limit'; }

Answer

range '0..10000';

Question 10

Which two mechanisms are used for congestion avoidance in a QoS policy? (Choose two.)

Accepted Answer

WRED. WRED (Weighted Random Early Detection) and tail drop are congestion avoidance mechanisms that manage queue fullness before congestion occurs.

Answer

CBWFQ

Answer

Policing

Answer

LLQ

Question 11

An SP uses NSO with a YANG service model to provision L3VPNs. Which database in NSO stores the configuration and state for all managed devices?

Accepted Answer

Configuration Database (CDB). NSO's CDB (Configuration Database) holds the configuration and state of all managed devices, acting as the authoritative data store.

Answer

Operational database

Answer

YANG repository

Answer

NED database

Question 12

An SP is designing a QoS policy for a customer VPN that carries voice, video conferencing, and bulk data. The voice traffic requires low latency, video conferencing requires assured bandwidth, and bulk data should use any remaining bandwidth. Which queuing strategy should be applied on the PE-CE link?

Accepted Answer

LLQ with CBWFQ. LLQ provides a strict priority queue for voice (low latency) and CBWFQ for other classes with bandwidth guarantees. Video conferencing can be assigned to a class with a bandwidth percent, and bulk data to the default class with fair queuing.

Answer

Policing with drop probability

Answer

FIFO with WRED

Answer

CBWFQ only

Question 13

An SP uses NSO to orchestrate MPLS L3VPN services. The service model is written in YANG, and the NED communicates with the PE routers. Which protocol does NSO use to push configuration to the network devices?

Accepted Answer

NETCONF. NSO can use NETCONF or RESTCONF southbound to communicate with network devices. NETCONF is the standard for configuration management.

Answer

CLI

Answer

PCEP

Answer

SNMP

Question 14

An SP is implementing Carrier-Grade NAT (CGNAT) to conserve IPv4 addresses. Which feature must be enabled to support applications that embed IP addresses in the payload, such as SIP or FTP?

Accepted Answer

ALG (Application Layer Gateway). Application Layer Gateway (ALG) is required to inspect and modify payloads for protocols like SIP and FTP that carry IP addresses in the data stream.

Answer

IPSec

Answer

Port forwarding

Answer

NAT traversal

Question 15

Which protocol is used by a BNG to authenticate and authorize subscribers?

Accepted Answer

RADIUS. BNG uses RADIUS for AAA (authentication, authorization, and accounting) of subscribers. RADIUS exchanges messages with a backend server to validate credentials and assign policies.

Answer

DIAMETER

Answer

LDAP

Answer

TACACS+