350-501 Practice Test 17 — 15 Questions

Question 1

When deploying IS-IS in a large service provider core, what is the recommended network type on Ethernet interfaces to improve scalability?

Accepted Answer

point-to-point. In a large service provider core, configuring IS-IS interfaces as point-to-point (network type point-to-point) improves scalability by eliminating the need for Designated Router (DIS) election and the associated pseudonode LSPs. This reduces the number of LSPs in the link-state database, lowers CPU and memory overhead, and speeds up convergence, which is critical in dense core networks.

Answer

loopback

Answer

point-to-multipoint

Answer

non-broadcast

Answer

broadcast

Question 2

In IS-IS, what is the purpose of the NET (Network Entity Title) address field SEL (Selector) byte?

Accepted Answer

Indicates that this is a router (always 0x00). The SEL byte is always 0x00 for routers, indicating that the address refers to the router itself rather than a specific service.

Answer

Identifies the application layer protocol

Answer

Identifies the area

Answer

Identifies the system ID

Question 3

Which TWO statements about QoS policy propagation via BGP (QPPB) are correct?

Accepted Answer

QPPB can be applied on inbound direction only.. QPPB can be applied on inbound direction only. QPPB uses BGP policy to classify traffic based on IP precedence or QoS group, and the classification is performed on incoming traffic before any routing decision. The outbound direction is not supported for QPPB classification.

Answer

QPPB is an IETF standard.

Answer

It uses MPLS EXP bits to propagate QoS.

Answer

It dynamically adjusts BGP attributes based on QoS policy.

Question 4

Which IS-IS TLV is used to carry Traffic Engineering (TE) information such as link bandwidth and TE metric in modern SP networks?

Accepted Answer

TLV 22 (extended IS reachability). IS-IS TE extensions use sub-TLVs within the extended IS reachability TLV (type 22). Specifically, TLV 135 (extended IP reachability) carries wide metrics, but TE information is carried in the extended IS reachability TLV (type 22) with sub-TLVs. The question asks for the TLV that carries TE info; the correct answer is the extended IS reachability TLV (type 22).

Answer

TLV 128 (IP reachability)

Answer

TLV 135 (extended IP reachability)

Answer

TLV 1 (area addresses)

Question 5

In IS-IS, what is the purpose of the System ID portion of the NET address?

Accepted Answer

It identifies the router within the area. The NET (Network Entity Title) consists of AFI, Area ID, System ID, and SEL. The System ID uniquely identifies a router within an area.

Answer

It identifies the area to which the router belongs

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It indicates the routing protocol version

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It specifies the ISO layer (SEL) for routing

Question 6

An engineer is designing an iBGP route reflector topology to improve scalability. Which two statements about BGP route reflectors are correct?

Accepted Answer

The originator-id attribute prevents the route from being advertised back to the originating router.. Route reflectors use cluster-id to detect loops and originator-id to prevent advertisement back to the originator. The non-client mesh requirement is eliminated with route reflectors.

Answer

All clients must be fully meshed with each other.

Answer

Route reflectors modify the AS_PATH attribute to prevent loops.

Answer

Route reflectors are only used in eBGP topologies.

Question 7

Which three BGP communities are standardized and commonly used for inter-AS traffic engineering? (Choose three.)

Accepted Answer

NO_EXPORT (0xFFFFFF01). Standard BGP communities include NO_EXPORT (0xFFFFFF01), NO_ADVERTISE (0xFFFFFF02), and LOCAL_AS (0xFFFFFF03). NO_EXPORT prevents advertisement to any eBGP peer; NO_ADVERTISE prevents advertisement to any peer; LOCAL_AS prevents advertisement outside the local AS.

Answer

NOPEER

Answer

INTERNET (0x00000000)

Question 8

An engineer is using NETCONF to retrieve the operational QoS statistics from a router. The response contains XML data but does not include the queueing statistics. What is the most likely reason?

Accepted Answer

The NETCONF filter did not include the correct YANG path for QoS statistics. NETCONF retrieves data based on YANG models. If the filter does not specify the correct YANG path for QoS queueing statistics, the server will not include that data in the response. The YANG data model for QoS (e.g., Cisco‑IOS‑XE‑qos‑oper.yang) defines specific paths for queueing counters; omitting or mis‑specifying the filter path results in an incomplete reply.

Answer

The user does not have enough privilege level

Answer

The statistics are only available via SNMP

Answer

The router is running an older IOS that does not support NETCONF

Question 9

A service provider wants to enable fast convergence for OSPF networks. Which feature should be enabled to detect link failures in sub-second time?

Accepted Answer

BFD. BFD (Bidirectional Forwarding Detection) provides fast failure detection for routing protocols like OSPF. OSPF can be configured to use BFD for sub-second convergence.

Answer

OSPF fast hello

Answer

OSPF SPF throttling

Answer

OSPF LSA throttling

Question 10

An SP is deploying NAT64 to allow IPv6-only clients to access IPv4 servers. Which address translation mechanism is used by NAT64 to map IPv6 addresses to IPv4 addresses?

Accepted Answer

Embedding IPv4 addresses in IPv6 addresses using a predefined prefix. NAT64 uses a well-known prefix (64:ff9b::/96) to embed IPv4 addresses into IPv6 addresses. The IPv4 address is appended to the prefix, creating an IPv6 address that represents the IPv4 destination.

Answer

IPv6-over-IPv4 tunneling

Answer

DNS64

Answer

Stateful translation of IPv6 to IPv4 using a pool of IPv4 addresses

Question 11

A service provider is designing an OSPF network for MPLS-TE. Which two OSPF LSA types are used to advertise Traffic Engineering information? (Choose two.)

Accepted Answer

LSA Type 10 (Area-local Opaque). OSPF uses opaque LSAs to carry TE information. Type 10 (area-local) and Type 11 (AS-scoped) opaque LSAs are used for TE. Type 9 is link-local.

Answer

LSA Type 1 (Router)

Answer

LSA Type 9 (Link-local Opaque)

Answer

LSA Type 4 (ASBR Summary)

Question 12

In IS-IS, a router is configured as L1 only. Which statement is true regarding its routing table?

Accepted Answer

It has a default route pointing to the nearest L1/L2 router.. An L1 router only knows routes within its own area. It uses the closest L1/L2 router as a default route to reach other areas. The L1/L2 router leaks a default route into the L1 area.

Answer

It learns all L2 routes from the backbone.

Answer

It learns inter-area routes via L1 LSPs.

Answer

It only uses narrow metrics.

Question 13

A service provider is implementing BGP route reflectors to scale iBGP. Which THREE mechanisms are used to prevent routing loops in a route reflector topology? (Choose three.)

Accepted Answer

CLUSTER_LIST. BGP route reflectors use several attributes to prevent loops: CLUSTER_LIST (cluster-id list), ORIGINATOR_ID (original router's RID), and the standard AS_PATH loop detection. Also, the route reflector does not reflect routes back to the client that sent it.

Answer

MED comparison

Answer

NEXT_HOP loop detection

Question 14

A service provider is configuring BGP route reflectors to scale iBGP. Which two mechanisms are used to prevent routing loops in a route reflector environment? (Choose two.)

Accepted Answer

CLUSTER_LIST. BGP route reflectors use the CLUSTER_LIST attribute (which includes the cluster-id) and the ORIGINATOR_ID attribute to prevent loops. CLUSTER_LIST lists the cluster-ids that a route has passed through, and ORIGINATOR_ID identifies the originator of the route to prevent it from being reflected back.

Answer

AS_PATH

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LOCAL_PREF

Answer

NEXT_HOP

Question 15

A service provider is designing an OSPF network with multiple areas. Which TWO area types allow external routes (Type 5 LSAs) to be injected into the area? (Choose two.)

Accepted Answer

Standard area. Standard areas and the backbone area (Area 0) allow Type 5 LSAs. Stub, totally stubby, and NSSA do not accept Type 5 LSAs (NSSA converts Type 7 to Type 5 at ABR, but internally uses Type 7).

Answer

NSSA

Answer

Stub area

Answer

Totally stubby area