350-501 Architecture Practice Test 13 — 15 Questions

Question 1

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

Accepted Answer

VRF. VRF (Virtual Routing and Forwarding) creates separate routing tables for each customer, ensuring isolation.

Answer

Route distinguisher (RD)

Answer

MPLS label

Answer

MP-BGP

Question 2

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. Q-in-Q adds an outer (service) VLAN tag (200) while preserving the inner (customer) VLAN tag (100).

Answer

Single tag: VLAN 100

Answer

Double tag: outer 100, inner 200

Answer

Single tag: VLAN 200

Question 3

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

Question 4

Which access technology is based on ITU-T G.984 and provides downstream speeds up to 2.488 Gbps?

Accepted Answer

GPON. GPON (Gigabit-PON) is defined by ITU-T G.984 with downstream up to 2.488 Gbps.

Answer

XGS-PON

Answer

DSL

Answer

EPON

Question 5

Which THREE of the following are key characteristics of Cisco IOS XR operating system?

Accepted Answer

Each routing protocol runs as a separate process.. Cisco IOS XR uses a microkernel operating system where each routing protocol runs as a separate process (A). It features a two-phase commit configuration model with atomic commit and rollback (B). It also supports non-stop forwarding (NSF) with graceful restart for high availability (C). Option D is incorrect because IOS XR does not have a monolithic kernel; it uses a microkernel. Option E is incorrect because while IOS XR separates control and data planes, it is not a distributed OS architecture; it is a microkernel-based OS designed for a single router.

Answer

Monolithic kernel where all processes run in a single memory space.

Answer

Distributed OS architecture with separate control and data planes.

Question 6

An SP is planning to offer L3VPN services. Which TWO components are essential for BGP/MPLS IP VPN operation?

Accepted Answer

VRF (Virtual Routing and Forwarding) on provider edge routers.. VRF (D) provides per-customer routing isolation, and MP-BGP with VPN-IPv4 address family (E) is used to exchange VPN routes between PEs. MPLS labels are used for data plane forwarding but are not considered control plane components for VPN operation.

Answer

Full mesh of IPsec tunnels between all PEs.

Answer

OSPF as the IGP within the MPLS core.

Answer

A single global routing table shared among all customers.

Question 7

Which access technology uses wavelength division multiplexing to provide symmetric gigabit speeds in fiber-optic networks?

Accepted Answer

XGS-PON. XGS-PON uses wavelength division multiplexing to support symmetric 10 Gbps speeds, while GPON is asymmetric and DSL/cable are copper-based.

Answer

Cable

Answer

GPON

Answer

DSL

Question 8

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 9

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

Accepted Answer

Fault isolation between protocols. Process separation prevents a failure in one protocol from affecting others, enhancing overall system stability.

Answer

Faster convergence by running protocols in parallel

Answer

Reduced memory usage by sharing libraries

Answer

Simplified configuration due to centralized processing

Question 10

A service provider wants to offer a point-to-point Layer 2 Ethernet service between two customer sites with strict SLAs. The solution must use MPLS pseudowires. Which MEF service type aligns with this requirement?

Accepted Answer

E-Line. E-Line is a point-to-point Ethernet service defined by MEF. E-LAN is multipoint, E-Tree is rooted multipoint, E-Access is for access to a service provider network.

Answer

E-Tree

Answer

E-Access

Answer

E-LAN

Question 11

Which component of the IOS XR architecture is responsible for managing the system configuration and providing a separation of control plane for multiple tenants?

Accepted Answer

Default SDR. The Default Secure Domain Router (SDR) in IOS XR manages the system configuration and provides logical separation of the control plane for multiple tenants. Other options: XR Config Manager is a tool for configuration management but not for tenant separation; Admin Plane handles administrative functions like system monitoring; LRO (Label Rewrite Engine) is used for label switching operations, unrelated to configuration or tenant separation.

Answer

XR Config Manager

Answer

Admin Plane

Answer

LRO (Label Rewrite Engine)

Question 12

A service provider is implementing EVPN to support multi-homing for a customer site. Which EVPN attribute ensures that only one of the PEs forwards traffic for a given Ethernet segment?

Accepted Answer

Designated Forwarder (DF) election. The ESI (Ethernet Segment Identifier) and designated forwarder election ensure single active forwarding per segment. DF election is used for multi-homing.

Answer

Label block

Answer

Route Target

Answer

Ethernet Tag ID

Question 13

An ISP wants to create separate virtual networks over a shared physical infrastructure to serve mobile broadband (eMBB), IoT (mMTC), and mission-critical services (uRLLC). Which technology enables this segmentation with per-slice resource guarantees?

Accepted Answer

Network Slicing using IETF and 3GPP frameworks. Network slicing divides the physical network into multiple virtual networks, each with dedicated resources for different service types. L3VPN, MPLS-TE, and VPLS do not provide per-slice resource guarantees natively.

Answer

MPLS Traffic Engineering

Answer

L3VPN with VRF

Answer

VPLS

Question 14

Which Cisco automation tool uses service models in YANG and communicates via NETCONF to orchestrate device configurations and lifecycle management?

Accepted Answer

Cisco Network Services Orchestrator (NSO). NSO (Network Services Orchestrator) uses YANG models and NETCONF for configuration management. Ansible, Cisco DNA Center, and Chef are other tools but NSO is specifically for service orchestration.

Answer

Ansible

Answer

Chef

Answer

Cisco DNA Center

Question 15

In a BGP/MPLS IP VPN, which technique ensures that customer traffic from different VPNs remains isolated on the same PE router?

Accepted Answer

Virtual Routing and Forwarding (VRF). VRF (Virtual Routing and Forwarding) provides separate routing tables per VPN on a PE router. MP-BGP carries VPN routes with labels, but isolation is achieved by VRF.

Answer

Route Target (RT)

Answer

MPLS labels

Answer

Route Distinguisher (RD)