350-501 Practice Test 15 — 15 Questions

Question 1

In an MPLS core, which forwarding mechanism do P routers use to forward packets for L3VPN?

Accepted Answer

MPLS label switching. P routers (core routers) perform label switching based on the MPLS label stack. They do not need to examine the IP header; they swap labels and forward accordingly.

Answer

MPLS label imposition

Answer

MPLS label disposition

Answer

IP routing based on destination IP

Question 2

An SP is designing a GPON access network. Which technology allows multiple ONUs to share the same fiber using different wavelengths for upstream and downstream?

Accepted Answer

Wavelength Division Multiplexing (WDM). GPON uses Wavelength Division Multiplexing (WDM) with different wavelengths for downstream (1490nm) and upstream (1310nm) on the same fiber.

Answer

Ethernet PON (EPON)

Answer

Time Division Multiple Access (TDMA)

Answer

Code Division Multiple Access (CDMA)

Question 3

In a Cisco IOS XR router, which statement best describes process separation?

Accepted Answer

Each protocol runs as a separate process with its own memory space. IOS XR runs each protocol as a separate process in protected memory, so a crash of one process does not affect others, improving stability.

Answer

Processes share memory to improve performance

Answer

All routing protocols run in a single process to reduce memory usage

Answer

Only BGP runs as a separate process; others are monolithic

Question 4

In Inter-AS MPLS Option B, which routers exchange labeled VPNv4 prefixes directly?

Accepted Answer

ASBR routers. In Inter-AS MPLS Option B, ASBR routers (Autonomous System Boundary Routers) exchange labeled VPNv4 prefixes directly across the AS boundary. This is achieved by having each ASBR perform two label operations: it pops the outer transport label from the VPNv4 prefix received from its own AS, then swaps the inner VPN label and forwards the labeled VPNv4 prefix to the neighboring ASBR in the adjacent AS. This direct exchange eliminates the need for end-to-end LSPs or MP-eBGP sessions between PE routers across different ASes.

Answer

PE routers

Answer

P routers

Answer

CE routers

Answer

Route reflectors

Question 5

Which Cisco router platform is designed for the aggregation layer and runs IOS XR, supporting both L2 and L3 services at high density?

Accepted Answer

Cisco ASR 9000. The ASR 9000 is a widely used aggregation router with IOS XR and supports L2/L3 services. CRS is core, NCS 5500 is edge/aggregation but more focused on 100GE, and ISR is enterprise.

Answer

Cisco NCS 5500

Answer

Cisco CRS

Answer

Cisco ISR 4000

Question 6

Which MEF service type defines a point-to-point Ethernet connection, often used for business connectivity?

Accepted Answer

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

Answer

E-Tree

Answer

E-Access

Answer

E-LAN

Question 7

A service provider is deploying L3VPN. Which mechanism ensures that customer routes are isolated and not leaked between different customers?

Accepted Answer

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

Answer

Route target (RT)

Answer

Route distinguisher (RD)

Answer

MPLS labels

Question 8

Which MPLS-based service provides point-to-point Ethernet connectivity over a service provider network, emulating a wire?

Accepted Answer

VPWS. VPWS (Virtual Private Wire Service) is a pseudowire that provides point-to-point L2VPN connectivity, emulating a physical wire.

Answer

L3VPN

Answer

VPLS

Answer

EVPN

Question 9

In IOS XR architecture, what is the purpose of Secure Domain Router (SDR)?

Accepted Answer

To enable process separation and fault isolation. SDR logically partitions a physical router into multiple independent routers, each with its own control plane and resources.

Answer

To encrypt control plane traffic

Answer

To provide a secure management plane

Answer

To aggregate multiple physical routers

Question 10

Which MEF service type provides a multipoint-to-multipoint Ethernet virtual connection?

Accepted Answer

E-LAN. E-LAN (Ethernet LAN) service provides multipoint-to-multipoint connectivity, as per MEF standards.

Answer

E-Access

Answer

E-Line

Answer

E-Tree

Question 11

Which MPLS-based service provides point-to-point Ethernet connectivity over a service provider network, also known as a pseudowire?

Accepted Answer

VPWS. VPWS (Virtual Private Wire Service) is a point-to-point L2VPN service that emulates a wire, also called a pseudowire.

Answer

EVPN

Answer

L3VPN

Answer

VPLS

Question 12

A service provider wants to automate service provisioning using NSO. Which protocol is typically used by NSO to configure network devices?

Accepted Answer

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

Answer

CLI scripting

Answer

SNMP

Answer

RESTCONF

Question 13

What is the function of the admin plane in IOS XR architecture?

Accepted Answer

It provides a management interface for configuring Secure Domain Routers (SDRs). The admin plane is a separate management context for administrative tasks such as configuring SDRs, managing hardware, and system-level settings. It provides isolation from the default SDR.

Answer

It runs routing protocols for the default SDR

Answer

It handles data plane forwarding

Answer

It is used for customer-facing VPN services

Question 14

A service provider is designing a network to support mobile backhaul for eMBB, uRLLC, and mMTC services. Which technology allows the physical network to be divided into virtual networks with dedicated resources for each service type?

Accepted Answer

Network slicing. Network slicing enables multiple virtual networks on a shared physical infrastructure, each with tailored performance characteristics.

Answer

Q-in-Q

Answer

MPLS TE

Answer

VPLS

Question 15

Which THREE are benefits of using EVPN over traditional VPLS? (Choose three.)

Accepted Answer

MAC address learning over the control plane (MAC mobility). EVPN offers BGP-based control plane, multi-homing support, and MAC mobility. VPLS traditionally uses LDP and does not natively support multi-homing or MAC mobility as effectively.

Answer

Simpler configuration without BGP

Answer

Lower latency due to MPLS label switching