350-501 Networking Practice Test 14 — 15 Questions

Question 1

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

Answer

LOCAL_PREF

Answer

NEXT_HOP

Question 2

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 3

A service provider is migrating from OSPF to IS-IS in the core network. They need to support Traffic Engineering and Segment Routing. Which IS-IS TLV must be supported to carry TE information?

Accepted Answer

TLV 22. IS-IS TLV 22 (Extended IS reachability) carries TE metrics and other attributes for traffic engineering. TLVs 128 and 130 are IP reachability TLVs; TLV 135 is for extended IP reachability.

Answer

TLV 130

Answer

TLV 135

Answer

TLV 128

Question 4

In an OSPF network, an engineer wants to reduce the size of the routing table and prevent external routes from being advertised into an area. Which area type should be configured?

Accepted Answer

Stub area. A stub area does not allow AS-external LSAs (type 5), reducing routing table size. NSSA allows limited external routes via type 7 LSAs.

Answer

Totally stubby area

Answer

Backbone Area 0

Answer

NSSA

Question 5

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 6

An ISP is implementing 6PE to provide IPv6 connectivity over an MPLS network that only supports IPv4 in the core. In 6PE, how are IPv6 prefixes carried across the MPLS backbone?

Accepted Answer

IPv6 prefixes are carried as IPv6 prefixes in MP-BGP with an IPv4 next-hop. 6PE uses MP-BGP to carry IPv6 prefixes (using the IPv6 unicast address family, AFI=2 SAFI=1) with an IPv4 next-hop address (the loopback of the peer 6PE router). The BGP session is over IPv4, but the NLRI carries IPv6 prefixes. MPLS labels are used to forward traffic across the IPv4-only core. It is important to note that 6PE does not use the VPNv6 address family (AFI=1 SAFI=128) — that is used for MPLS L3VPN.

Answer

IPv6 prefixes are transported over an IPv6 MPLS core using LDPv6

Answer

IPv6 prefixes are encapsulated in IPv4 tunnels with GRE

Answer

IPv6 prefixes are converted to IPv4 using NAT64 before MPLS forwarding

Question 7

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

Answer

It indicates the routing protocol version

Answer

It specifies the ISO layer (SEL) for routing

Question 8

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 9

A service provider is deploying BGP PIC (Prefix Independent Convergence) for edge routers. What is the primary benefit of BGP PIC?

Accepted Answer

It provides fast convergence by pre-installing backup paths in the FIB. BGP PIC provides fast failover by precomputing backup paths in the forwarding table, enabling sub-second convergence upon failure, independent of the number of prefixes.

Answer

It reduces the number of BGP updates during a flap

Answer

It reduces the memory usage on the router

Answer

It eliminates the need for BFD

Question 10

In OSPFv3, what change was introduced compared to OSPFv2 for supporting IPv6?

Accepted Answer

OSPFv3 runs over IPv6 and uses link-local addresses for adjacencies. OSPFv3 runs per-link instead of per-subnet, uses link-local addresses for neighbor discovery, and separates the protocol from addressing by using LSAs with IPv6 prefix information.

Answer

OSPFv3 uses the same LSA types as OSPFv2

Answer

OSPFv3 supports only point-to-point network types

Answer

OSPFv3 eliminates the need for a router ID

Question 11

Which IS-IS metric type is required for traffic engineering and segment routing?

Accepted Answer

Wide metrics. IS-IS wide metrics (TLV 22 and 135) use 24-bit or 32-bit values, allowing higher link costs needed for TE. Narrow metrics are limited to 6 bits.

Answer

Narrow metrics

Answer

Extended metrics

Answer

Default metrics

Question 12

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 13

In BGP route selection, when comparing two routes with the same LOCAL_PREF, which attribute is considered next?

Accepted Answer

Locally originated routes (prefer routes originated by the local router). After LOCAL_PREF, the next step in BGP best path selection is whether the route was originated locally (via network or aggregate command). Then AS_PATH length is considered.

Answer

MED

Answer

AS_PATH length

Answer

eBGP over iBGP

Question 14

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 15

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)