350-501 Architecture Practice Test 14 — 15 Questions

Question 1

Which TWO of the following are characteristics of the IOS XR operating system architecture? (Select two.)

Accepted Answer

Commit/rollback configuration model. Option B is correct because IOS XR uses a commit-based configuration model: changes are staged in a candidate configuration and only take effect when the operator issues the commit command, with the ability to roll back to previous configurations. Option D is correct because IOS XR is a distributed operating system in which processes run in separate protected memory spaces, and control-plane functions are distributed across the route processor and line cards rather than sharing one monolithic image. Option A is incorrect because IOS XR does not apply configuration changes immediately; they require an explicit commit. Option C is incorrect because IOS XR is not a monolithic kernel with shared memory; it is built on a microkernel-style, modular architecture with process isolation. Option E is incorrect because line cards do not all run a single shared control-plane process; IOS XR distributes processes across nodes, with each line card running its own processes.

Answer

Configuration changes take effect immediately without commit

Answer

Monolithic kernel where all processes share memory

Answer

All line cards run a single control plane process

Question 2

Which THREE of the following are benefits of using EVPN over traditional VPLS for L2VPN services? (Select three.)

Accepted Answer

Integrated L2 and L3 services (e.g., IRB). EVPN offers BGP control plane, multi-homing with ESI, and integrated L2/L3 services.

Answer

Supports only point-to-point pseudowires

Answer

Eliminates the need for VPLS

Question 3

Which TWO access technologies are considered fiber-based solutions for service provider access networks? (Select two.)

Accepted Answer

XGS-PON. GPON and XGS-PON are fiber-based PON technologies.

Answer

WiMAX

Answer

Cable (DOCSIS)

Answer

DSL

Question 4

A service provider wants to provide a point-to-point Ethernet service between two customer sites with strict Service Level Agreements (SLAs). Which MEF service type should be used?

Accepted Answer

E-Line. E-Line is the MEF (Metro Ethernet Forum) service type that provides a point-to-point Ethernet Virtual Connection (EVC) between exactly two customer sites, which is ideal for strict SLAs because it offers dedicated, predictable bandwidth and performance. E-Line services are defined in MEF 6.1 and support both Ethernet Private Line (EPL) and Ethernet Virtual Private Line (EVPL) variants, ensuring low latency, jitter, and frame loss. This directly matches the requirement for a point-to-point service with SLAs.

Answer

E-LAN

Answer

E-Access

Answer

E-Tree

Question 5

In Cisco IOS XR architecture, using Secure Domain Routers (SDRs) allows partitioning a physical router into multiple logical routers. Which statement about admin plane and SDRs is correct?

Accepted Answer

The admin plane is a separate SDR that manages hardware resources and system-level functions, while the default SDR handles routing and forwarding.. In Cisco IOS XR, the admin plane is a separate Secure Domain Router (SDR) that manages hardware resources and system-level functions, while the default SDR handles routing and forwarding. The admin plane is responsible for chassis management, software installation, and other system-wide tasks, and it is isolated from the default SDR for security and stability.

Answer

The admin plane runs only on route processor cards, while default SDR runs on line cards.

Answer

The admin plane and default SDR are the same logical entity and share all configuration.

Answer

SDRs are only supported on Cisco CRS, not on ASR 9000.

Question 6

Which access technology uses a passive optical splitter to deliver broadband services to multiple subscribers over a single fiber?

Accepted Answer

GPON. GPON (Gigabit Passive Optical Network) uses a passive optical splitter to divide a single fiber's signal among multiple subscribers, enabling point-to-multipoint broadband delivery without active electronics in the field. The splitter is unpowered, reducing cost and complexity while allowing service to many homes from one feeder fiber.

Answer

Cable (DOCSIS)

Answer

Metro Ethernet

Answer

DSL (Digital Subscriber Line)

Question 7

An SP is deploying EVPN to provide both L2 and L3 VPN services. Which advantage does EVPN offer over traditional VPLS for multi-homing?

Accepted Answer

EVPN provides faster convergence and active-active multi-homing using Ethernet Segment Identifier (ESI) and Designated Forwarder (DF) election.. EVPN uses ESI-based multi-homing with BGP control plane, offering faster convergence and active-active load balancing compared to VPLS's active/standby model.

Answer

EVPN uses a single MAC address per PE to reduce forwarding table size.

Answer

EVPN supports only active/standby redundancy, similar to VPLS.

Answer

EVPN requires MPLS in the core, whereas VPLS can use IP-only.

Question 8

In IOS XR, each routing protocol runs as a separate process. What is the primary benefit of this architecture?

Accepted Answer

It allows each protocol to be upgraded independently without a system reboot.. IOS XR's modular architecture runs each routing protocol (BGP, OSPF, ISIS, etc.) as an independent process with its own memory space. This isolation means a protocol can be restarted, upgraded, or have its configuration changed without rebooting the router or affecting other protocols, delivering hitless software upgrades and fault containment.

Answer

It simplifies configuration by combining all protocols into a single file.

Answer

It reduces memory consumption by sharing code between processes.

Answer

It improves forwarding performance by dedicating CPU cores to each protocol.

Question 9

Which MEF service type is used for multipoint-to-multipoint Ethernet connectivity, such as a corporate LAN extension across multiple sites?

Accepted Answer

E-LAN. E-LAN (Ethernet LAN) is the MEF service type that provides multipoint-to-multipoint Ethernet connectivity, allowing any site to communicate with any other site as if they were on the same LAN. It is the standard choice for corporate LAN extension across multiple locations. E-Line is point-to-point and E-Tree is rooted multipoint, so neither matches the multipoint-to-multipoint requirement.

Answer

E-Line

Answer

E-Tree

Answer

E-Access

Question 10

A service provider is implementing network slicing for 5G services. Which of the following is NOT a typical characteristic of a network slice?

Accepted Answer

Slices require dedicated physical infrastructure per slice.. Network slicing in 5G is built on network function virtualization (NFV) and software-defined networking (SDN), allowing multiple logical networks to share the same physical infrastructure. Each slice is a virtualized, isolated instance with its own resources and performance characteristics, so requiring dedicated physical infrastructure per slice contradicts the fundamental efficiency and flexibility that slicing provides. Therefore, option C is NOT a typical characteristic.

Answer

Each slice can have its own dedicated virtualized functions and resources.

Answer

Slices can be customized for specific service types like eMBB, uRLLC, or mMTC.

Answer

Slices are isolated from each other in terms of performance and security.

Question 11

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. In IOS XR's two-stage configuration model, the 'commit' command applies the candidate configuration to the running configuration as a single atomic transaction. All changes in the target configuration are validated and applied together, or none are applied if validation fails. This atomicity is the defining feature of IOS XR's commit-based model.

Answer

save config

Answer

apply-changes

Answer

copy running-config startup-config

Question 12

Which Cisco automation tool is designed for service modeling with YANG and provides lifecycle management of network services?

Accepted Answer

Cisco Network Services Orchestrator (NSO). Cisco NSO (Network Services Orchestrator) uses YANG models and NETCONF to manage service lifecycle.

Answer

Cisco APIC

Answer

Cisco Prime Infrastructure

Answer

Cisco DNA Center

Question 13

In BGP/MPLS IP VPN (L3VPN), which component provides customer isolation by maintaining separate routing tables per customer?

Accepted Answer

VRF. A VRF (Virtual Routing and Forwarding) instance maintains a separate routing table per customer on the PE router, providing logical isolation of customer routes. Each VRF is associated with interfaces and BGP sessions, ensuring customer traffic is kept separate.

Answer

Route distinguisher (RD)

Answer

MPLS label

Answer

MP-BGP

Question 14

An SP is designing a metro Ethernet network using Q-in-Q. A customer uses VLAN ID 100 on their network, and the SP assigns service VLAN 200. Which frame format is used on the SP network?

Accepted Answer

Double tag: outer 200, inner 100. In Q-in-Q (802.1ad), the service provider encapsulates the customer's frame by adding an outer service VLAN tag (S-VLAN) while preserving the customer's original VLAN tag (C-VLAN). The SP assigns S-VLAN 200, and the customer uses C-VLAN 100, so the frame on the SP network has an outer tag of 200 and an inner tag of 100.

Answer

Single tag: VLAN 100

Answer

Double tag: outer 100, inner 200

Answer

Single tag: VLAN 200

Question 15

Which Cisco SP router platform uses IOS XR and is commonly deployed at the aggregation layer, supporting both L2 and L3 services?

Accepted Answer

Cisco ASR 9000. Cisco ASR 9000 is an aggregation router running IOS XR, suitable for L2/L3 services.

Answer

Cisco CRS

Answer

Cisco ASR 1000

Answer

Cisco NCS 540