350-501 Practice Test 43 — 15 Questions

Question 1

A service provider is deploying a Broadband Network Gateway (BNG) for subscriber management. Which protocol is used by the BNG to authenticate subscribers via a RADIUS server?

Accepted Answer

RADIUS. The BNG acts as a RADIUS client and uses RADIUS protocol to send authentication requests (Access-Request) for PPPoE or IPoE sessions.

Answer

LDAP

Answer

Diameter

Answer

TACACS+

Question 2

An automation engineer is writing a Python script using Cisco's pyATS library to validate QoS configurations across a fleet of routers. The script runs without errors but reports that all routers are compliant even though some are not. What is the most likely issue?

Accepted Answer

The script uses a single 'show running-config' without filtering, and the parser fails to locate QoS policies applied under interfaces. The pyATS parser for 'show running-config' without filtering may not recursively parse QoS policy-map configurations applied under interfaces. When the script uses a single unfiltered 'show running-config', the parser might fail to extract QoS policies nested under interface sub-configurations, leading to false compliance reports. This is a common issue where the parser's data model does not map deeply nested CLI structures like 'service-policy input/output' under interfaces.

Answer

The pyATS library does not support QoS features for the specific platform

Answer

The testbed credentials are incorrect but the script still returns compliant

Answer

The script is parsing the startup-config instead of running-config

Question 3

A service provider is designing a greenfield MPLS core and wants to minimize control-plane complexity while still supporting traffic engineering. They plan to use Segment Routing with MPLS. Which statement about Segment Routing in this context is accurate?

Accepted Answer

Segment Routing reduces the number of protocols required in the core.. Segment Routing (SR-MPLS) eliminates the need for a separate label distribution protocol like LDP or RSVP-TE. The MPLS labels are derived directly from the IGP (IS-IS or OSPF) extensions, reducing control-plane complexity while still enabling traffic engineering via SR-TE policies and flexible path computation.

Answer

Segment Routing only works with IPv6 data plane.

Answer

Segment Routing uses RSVP-TE for label distribution.

Answer

Segment Routing requires TI-LFA to be enabled for traffic engineering.

Question 4

Which Cisco router platform is designed for high-density 100GE and uses IOS XR, making it suitable for the core/backbone of a service provider network?

Accepted Answer

Cisco CRS. Cisco CRS (Carrier Routing System) is a high-end core router supporting high-density 100GE and running IOS XR.

Answer

Cisco NCS 5500

Answer

Cisco ASR 9000

Answer

Cisco ISR 4400

Question 5

Which MEF service type provides a point-to-point Ethernet connection between two user-network interfaces (UNIs)?

Accepted Answer

E-Line. E-Line is the MEF service for point-to-point Ethernet connectivity.

Answer

E-LAN

Answer

E-Tree

Answer

E-Access

Question 6

Which TWO are characteristics of the access layer in a service provider network? (Choose two.)

Accepted Answer

Provides connectivity to end customers. Access layer provides connectivity to end users and aggregates traffic from various technologies.

Answer

Implements inter-AS MPLS

Answer

Uses MPLS label switching for core traffic

Answer

Performs BGP route reflection

Question 7

In IOS XR, which process is responsible for managing the configuration database and commit operations?

Accepted Answer

confd. The configuration management process handles commit/rollback and stores configuration in a database.

Answer

fman

Answer

sysmgr

Answer

rib

Question 8

A service provider is using NSO for service orchestration. Which protocol does NSO use to communicate with network devices for configuration?

Accepted Answer

NETCONF. NSO uses NETCONF as the primary protocol for device configuration, leveraging YANG models.

Answer

SNMP

Answer

RESTCONF

Answer

CLI scripting

Question 9

A service provider is deploying network slicing for 5G services. Which slice type is characterized by low latency and high reliability for applications like autonomous driving?

Accepted Answer

uRLLC. uRLLC (Ultra-Reliable Low-Latency Communications) is designed for latency-critical and reliable applications.

Answer

FMC

Answer

eMBB

Answer

mMTC

Question 10

A network engineer is troubleshooting an OSPF adjacency issue between two routers connected via a serial link. The routers are configured with point-to-point network type. The adjacency stays in EXSTART state. What is the most likely cause?

Accepted Answer

Mismatched MTU.. On a point-to-point OSPF link, the EXSTART state indicates that the routers have formed a bidirectional communication (2WAY) and are now negotiating the master/slave relationship for database description (DBD) packet exchange. A mismatched MTU between the two interfaces causes the DBD packets to be dropped or rejected, preventing the adjacency from progressing beyond EXSTART. This is a common issue on serial links where one side may have a different MTU configured.

Answer

Mismatched OSPF area ID.

Answer

Mismatched hello/dead intervals.

Answer

Duplicate router IDs.

Question 11

A service provider needs to offer L3VPN services with customer isolation. Which technology is used to maintain separate routing tables for different customers on a single PE router?

Accepted Answer

VRF. VRF (Virtual Routing and Forwarding) instances provide separate routing tables per customer, ensuring isolation in L3VPN.

Answer

VLAN

Answer

Route distinguisher (RD)

Answer

MPLS labels

Question 12

Which Cisco platform is best suited for the core/backbone role of a large service provider network, offering high scalability and MPLS forwarding capacity?

Accepted Answer

Cisco CRS. Cisco CRS (Carrier Routing System) is designed for the core with high capacity and MPLS capabilities.

Answer

Cisco ASR 1000

Answer

Cisco ASR 9000

Answer

Cisco NCS 5500

Question 13

In the context of IOS XR commit/rollback configuration model, which command is used to apply a set of configuration changes as a single atomic operation?

Accepted Answer

commit. The 'commit' command applies changes atomically; if any part fails, the entire commit is rejected.

Answer

save config

Answer

apply-changes

Answer

copy running-config startup-config

Question 14

A service provider is deploying a new MPLS core network and needs a router platform that supports high-scale MPLS forwarding and offers a modular operating system. Which Cisco platform is best suited for this role?

Accepted Answer

Cisco CRS. The Cisco CRS is a carrier-grade router designed for the core/backbone with high MPLS scalability and IOS XR modularity. ASR 9000 is more for aggregation, NCS for edge/aggregation.

Answer

Cisco ASR 9000

Answer

Cisco 8000 series

Answer

Cisco NCS 5500

Question 15

A metro Ethernet provider needs to scale customer VLANs beyond the 4,096 limit by encapsulating customer VLAN tags with an outer service provider tag. Which IEEE standard is used?

Accepted Answer

802.1ad (Q-in-Q). Q-in-Q (802.1ad) adds an outer VLAN tag to extend VLAN space. 802.1ah is for MAC-in-MAC, 802.1Q is the basic standard, and 802.1ak is not related.

Answer

802.1ah (Provider Backbone Bridging)

Answer

802.1Q

Answer

802.1ak