350-501 Practice Exam 58 — 20 Questions

Question 1

A service provider is implementing BGP PIC (Prefix Independent Convergence) for its core network. Which mechanism does BGP PIC primarily rely on to achieve fast convergence?

Accepted Answer

Precomputed backup paths (BGP PIC edge). BGP PIC uses precomputed backup paths (e.g., via BGP PIC edge or BGP add-path) to switch traffic upon failure without waiting for BGP convergence.

Answer

BFD

Answer

Route reflectors

Answer

Communities

Question 2

In OSPFv3, which of the following is true about the protocol's operation?

Accepted Answer

It runs per-link rather than per-subnet. OSPFv3 runs per-link, not per-subnet; it uses link-local addresses for adjacencies and floods LSA types specific to IPv6.

Answer

It requires IPv4 to function

Answer

It uses the same LSA types as OSPFv2

Answer

It does not support authentication

Question 3

An ISP is implementing 6PE for IPv6 transport over MPLS. Which two conditions are required for 6PE to work? (Choose two.)

Accepted Answer

BGP multiprotocol extensions for IPv6. 6PE requires BGP to carry IPv6 prefixes with an IPv4 next-hop (MPLS label), and the core MPLS network must support IPv4 LSPs.

Answer

IPv6 MPLS LSPs in the core

Answer

IPv6 next-hop in BGP updates

Answer

6PE requires 6VPE

Question 4

A network administrator needs to automate the deployment of a new QoS policy on dozens of provider edge routers. Which Cisco tool is best suited for this purpose?

Accepted Answer

Cisco Network Services Orchestrator (NSO). Cisco Network Services Orchestrator (NSO) is the correct tool because it provides model-driven orchestration and automation for deploying and managing network configurations across hundreds of devices using YANG data models and NETCONF. For QoS policy deployment, NSO can push consistent service definitions (e.g., class-maps, policy-maps, service-policy) to multiple provider edge routers simultaneously, ensuring compliance and reducing manual errors.

Answer

Cisco SecureX

Answer

Cisco Prime Infrastructure

Answer

Cisco ISE

Question 5

Which IS-IS level is used for routing within an area?

Accepted Answer

Level 1. IS-IS uses Level 1 (L1) for intra-area routing and Level 2 (L2) for inter-area routing.

Answer

Level 2

Answer

Level 0

Answer

Level 1/2

Question 6

In IS-IS, what is the result of configuring wide metrics on all interfaces?

Accepted Answer

Higher metric values are supported for traffic engineering. Wide metrics (24-bit or 32-bit) allow values up to 16,777,215 or higher, enabling TE and faster convergence with precise metric adjustments.

Answer

Only L2 routers can use wide metrics

Answer

Metrics are limited to 63

Answer

IS-IS TLVs are backward compatible with narrow metrics

Question 7

An SP network uses MPLS to provide IPv6 connectivity over an IPv4 backbone using 6PE. Which BGP extension is required on the provider edge routers to exchange IPv6 prefixes with an IPv4 next-hop?

Accepted Answer

BGP multiprotocol extensions (MP-BGP) with IPv6 address family. 6PE uses BGP multiprotocol extensions (MP-BGP) with an AFI of 2 (IPv6) and SAFI of 1 (unicast), and the next-hop is encoded as an IPv4 address using the 'next-hop' attribute.

Answer

BGP route reflection

Answer

BGP confederation

Answer

BGP prefix-independent convergence (PIC)

Question 8

An SP is deploying IS-IS fast convergence using Partial Route Computation (PRC). Under which condition does PRC occur?

Accepted Answer

When a prefix is added or removed without topology change. PRC is triggered when a prefix changes but the topology remains unchanged. It recalculates only the affected prefixes, not the entire SPF tree.

Answer

When the IS-IS metric changes

Answer

When the system ID changes

Answer

When a new adjacency is formed

Question 9

Which BGP attribute is used to prefer a specific entry point into an AS when multiple ASBRs are advertising the same prefix to a neighboring AS?

Accepted Answer

MED. MED (Multi-Exit Discriminator) is used to influence the inbound traffic by suggesting the preferred entry point.

Answer

LOCAL_PREF

Answer

WEIGHT

Answer

AS_PATH

Question 10

Which BGP attribute is used to influence inbound traffic to an AS by advertising a preferred path to a neighbor AS?

Accepted Answer

MED. MED (Multi-Exit Discriminator) is sent to a neighboring AS to suggest the best entry point into the local AS. Lower MED is preferred.

Answer

WEIGHT

Answer

LOCAL_PREF

Answer

AS_PATH

Question 11

An ISP is implementing MAP-T to transition to IPv6. Which of the following best describes MAP-T?

Accepted Answer

It uses stateless translation between IPv4 and IPv6 at the network edge. MAP-T (Mapping of Address and Port using Translation) uses IPv4-IPv6 translation (stateless NAT64) to allow IPv4 devices to communicate over an IPv6 network. It is an IPv6 transition mechanism.

Answer

It encapsulates IPv6 packets in IPv4 headers for transport over an IPv4 core

Answer

It requires both IPv4 and IPv6 addresses on every router

Answer

It tunnels IPv4 packets over IPv6 using GRE

Question 12

What is the purpose of the SEL (NSAP Selector) field in an IS-IS NET address?

Accepted Answer

It is always set to 0x00 for the device itself.. In IS-IS, the NET (Network Entity Title) address includes an SEL byte. The SEL is always set to 0x00 for the device itself, as it identifies the network layer entity, not a specific service.

Answer

It identifies the system ID of the router.

Answer

It is used to select the routing protocol.

Answer

It identifies the area within the routing domain.

Question 13

A service provider is designing an OSPF network with multiple areas. Which two area types prevent Type 5 LSAs from being flooded? (Choose two.)

Accepted Answer

Stub area. Stub and NSSA areas both block Type 5 LSAs; totally stubby also blocks Type 3/4.

Answer

Standard area

Answer

Totally stubby area

Answer

Backbone area

Question 14

A service provider uses BGP route reflectors to scale iBGP. A route reflected from a route reflector arrives at a client with the originator-id set. What is the purpose of the originator-id attribute?

Accepted Answer

To prevent routing loops by ensuring the route is not accepted if the originator-id matches the local router-id. The originator-id is set by the route reflector to the router-id of the originating router in the AS. It prevents routing loops by allowing a route to be ignored if the originator-id matches the receiving router's ID.

Answer

To identify the route reflector that reflected the route

Answer

To indicate the cluster-id of the route reflector

Answer

To carry the next-hop information for IPv6 prefixes

Question 15

A service provider is implementing BGP security using RPKI. Which three components are required for RPKI-based BGP origin validation? (Choose three.)

Accepted Answer

Route Origin Authorization (ROA). RPKI requires: 1) ROA (Route Origin Authorization) created by the prefix holder; 2) Relying Party (cache server) that fetches and validates ROAs; 3) RTR protocol to download the VRP (Validated ROA Payload) to routers. BGPsec is a separate standard for path validation. IS-IS is not involved.

Answer

BGPsec path validation

Answer

IS-IS routing protocol

Question 16

A service provider is implementing MAP-T (Mapping of Address and Port using Translation) to transition customers from IPv4 to IPv6. Which two characteristics of MAP-T are true? (Choose two.)

Accepted Answer

MAP-T employs a Border Router that performs translation between IPv4 and IPv6. MAP-T uses stateful or stateless translation between IPv4 and IPv6, and it uses a Border Router (BR) that performs translation. MAP-T does not use encapsulation; it uses translation (NAT). MAP-T also uses a Domain Name System (DNS) but that is not unique. The key characteristics: it uses a BR for translation and can be stateless.

Answer

MAP-T is primarily used for IPv6-to-IPv4 communication only

Answer

MAP-T requires a dedicated IPv6 prefix for each customer

Answer

MAP-T uses encapsulation to transport IPv4 packets over an IPv6 network

Question 17

An engineer is configuring BGP route reflectors to scale iBGP. Which TWO attributes are used to prevent routing loops in a route reflector cluster? (Choose two.)

Accepted Answer

ORIGINATOR_ID. CLUSTER_LIST and ORIGINATOR_ID are used to prevent loops. CLUSTER_LIST is a sequence of cluster IDs; ORIGINATOR_ID identifies the originator.

Answer

NEXT_HOP

Answer

LOCAL_PREF

Answer

AS_PATH

Question 18

An SP network uses OSPF with RSVP-TE for traffic engineering. Which OSPF extension is required to advertise TE link parameters such as maximum reservable bandwidth?

Accepted Answer

OSPF Type 10 Opaque LSAs. OSPF TE extensions are defined in RFC 3630, which introduces the Opaque LSA (Type 9, 10, 11). Specifically, Type 10 Opaque LSAs carry TE information. The TE LSA is carried in an Opaque LSA of area scope (Type 10).

Answer

OSPF Type 7 LSAs

Answer

OSPF Type 11 Opaque LSAs

Answer

OSPF Type 5 LSAs

Question 19

A service provider uses OSPFv3 for IPv6 routing in the core. Which statement correctly describes OSPFv3 adjacency formation on a broadcast multiaccess network?

Accepted Answer

The Designated Router (DR) is elected to reduce the number of adjacencies and LSDB flooding.. OSPFv3 operates similarly to OSPFv2 on broadcast networks, electing a DR and BDR using Hello protocol, and forming adjacencies with the DR.

Answer

OSPFv3 does not use DR/BDR election; instead, it forms full mesh adjacencies.

Answer

All routers on the network form full adjacencies with every other router.

Answer

The DR is elected based on the highest router ID, with a tiebreaker of highest interface priority.

Question 20

In IS-IS, what is the purpose of the Partial Route Computation (PRC)?

Accepted Answer

To recompute only the routes that are affected by a change in IP reachability. PRC recomputes only affected routes when a leaf changes, without full SPF, enabling faster convergence.

Answer

To compute the entire SPF tree after a topology change

Answer

To calculate the shortest path to all destinations in the L2 backbone

Answer

To repair IS-IS adjacency after link failure