350-501 Networking — Timed 20 Questions

Question 1

An SP engineer is configuring IS-IS on a router and specifies a NET address of 49.0001.1921.6800.1001.00. What does the '00' at the end represent?

Accepted Answer

SEL (NSAP Selector). The last two octets of an IS-IS NET address represent the SEL (NSAP Selector), which is always 00 for a router.

Answer

AFI

Answer

System ID

Answer

Area ID

Question 2

In an OSPF network, an engineer wants to minimize the size of the routing table in a non-backbone area while still allowing the area to learn external routes from other ASs. Which OSPF area type should be configured?

Accepted Answer

NSSA. A Not-So-Stubby Area (NSSA) allows importing external routes as Type 7 LSAs while still blocking Type 5 LSAs from other areas.

Answer

Stub area

Answer

Totally stubby area

Answer

Backbone area 0

Question 3

Which BGP attribute is NOT considered in the BGP best path selection process when all other attributes are equal and the routes are from different ASs?

Accepted Answer

MED. Weight is Cisco-specific and considered first, but it is not a standard BGP attribute; it is considered before LOCAL_PREF.

Answer

LOCAL_PREF

Answer

AS_PATH length

Answer

Weight

Question 4

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 5

In IS-IS, which type of LSP is used to advertise prefix information for IPv4 and IPv6 in a modern SP network that supports traffic engineering?

Accepted Answer

TLV 135 (Extended IP Reachability). TLV 135 for IPv4 (extended IP reachability) and TLV 236 for IPv6 (IPv6 reachability) are used in IS-IS for prefix advertisement.

Answer

TLV 2 (IS Neighbors)

Answer

TLV 1 (Area Addresses)

Answer

TLV 22 (IS Extended Neighbors)

Question 6

An OSPF network is configured with RSVP-TE. Which OSPF extension is used to advertise TE link attributes such as bandwidth and administrative group?

Accepted Answer

OSPF Type 10 Opaque LSA. OSPF TE extensions use Opaque LSAs (Type 9, 10, 11) to carry TE information. Type 10 (area-local) is commonly used for TE.

Answer

OSPF Type 1 LSA

Answer

OSPF Type 5 LSA

Answer

OSPF Type 7 LSA

Question 7

In BGP route reflection, what is the purpose of the ORIGINATOR_ID attribute?

Accepted Answer

To prevent routing loops by ensuring that a route is not reflected back to its originator. ORIGINATOR_ID is a non-transitive optional attribute that identifies the router that originated the route into the iBGP domain, used to prevent loops.

Answer

To indicate the next-hop IP address

Answer

To identify the route reflector

Answer

To carry the community value

Question 8

An SP is implementing IPv6 transition using MAP-T. Which encapsulation method does MAP-T use?

Accepted Answer

IPv4-IPv6 translation (NAT64-like). MAP-T (Mapping of Address and Port using Translation) uses IPv4-IPv6 translation (stateless NAT64-like) at the customer edge, not encapsulation.

Answer

MPLS label switching

Answer

IPv4 in IPv6 encapsulation

Answer

IPv6 in IPv4 encapsulation

Question 9

In IS-IS, which metric type supports traffic engineering (TE) and is required for segment routing?

Accepted Answer

Wide metrics (TLV 135/236/22). IS-IS wide metrics (TLV 135/236/22) support TE and segment routing; narrow metrics (TLV 128/130) are limited to 6-bit metrics.

Answer

Default metric (TLV 2)

Answer

Narrow metrics (TLV 128/130)

Answer

TE metric (TLV 138)

Question 10

Which BGP attribute influences inbound traffic to an AS by affecting the path selection of eBGP peers?

Accepted Answer

MED. MED (Multi-Exit Discriminator) is used to influence inbound traffic by suggesting to a neighbor AS which path to use.

Answer

LOCAL_PREF

Answer

Weight

Answer

AS_PATH

Question 11

An SP is deploying IS-IS fast convergence. Which mechanism triggers an immediate SPF computation when a neighbor fails?

Accepted Answer

BFD (Bidirectional Forwarding Detection). BFD (Bidirectional Forwarding Detection) provides sub-second failure detection and triggers SPF/PRC.

Answer

Partial Route Computation (PRC)

Answer

Event-driven SPF

Answer

IS-IS Hello multiplier

Question 12

In a BGP confederation, which AS number is used in the AS_PATH to prevent loops within the confederation?

Accepted Answer

Private AS numbers (64512-65535). Confederation uses private AS numbers (from 64512 to 65535) for sub-ASs, and these are prepended to the AS_PATH but not shown to external peers.

Answer

The same AS number as the confederation ID

Answer

Public AS numbers

Answer

No AS number is prepended

Question 13

An SP engineer is designing an OSPF network and wants to reduce the number of LSAs in a stub area. Which TWO area types would block Type 5 LSAs but allow Type 3 LSAs? (Choose two.)

Accepted Answer

NSSA. Stub and NSSA allow Type 3 LSAs but block Type 5 LSAs. Totally stubby blocks both Type 3 and Type 5.

Answer

Totally stubby area

Answer

Backbone area 0

Answer

Normal area

Question 14

Which THREE BGP attributes are considered in the best path selection process before comparing IGP metric to the next-hop? (Choose three.)

Accepted Answer

AS_PATH length. Weight, LOCAL_PREF, and AS_PATH length are considered before IGP metric. MED comes after AS_PATH.

Answer

MED

Answer

eBGP over iBGP

Question 15

An SP is deploying IPv6 using 6VPE. Which THREE components are required? (Choose three.)

Accepted Answer

Customer edge (CE) routers with IPv6 connectivity. 6VPE requires MPLS core, MP-BGP with VPNv6 address family, and CE routers running IPv6. LDP is used for label distribution in the core.

Answer

6rd tunneling

Answer

NAT64 translation

Question 16

An engineer is configuring IS-IS in a service provider network. The network uses wide metrics for traffic engineering. Which TLV is mandatory for IS-IS to carry traffic engineering (TE) information in accordance with RFC 5305?

Accepted Answer

TLV 22 (Extended IS Reachability). TLV 22 (Extended IS Reachability) is the mandatory TLV for IS-IS TE, defined in RFC 5305.

Answer

TLV 135 (Extended IP Reachability)

Answer

TLV 229 (Multi-Topology Reachable IPv4 Prefixes)

Answer

TLV 128 (IP Internal Reachability)

Question 17

In an IS-IS network, a router has a NET of 49.0001.1921.6800.1001.00. What does the '00' at the end represent?

Accepted Answer

SEL (NSAP Selector). The last byte '00' is the SEL (NSAP Selector), which is always '00' for IS-IS routing.

Answer

System ID

Answer

AFI

Answer

Area ID

Question 18

A service provider is deploying OSPFv3 for IPv6 in its core. The network uses multiple areas. Which LSA type is used by OSPFv3 to advertise prefix information for inter-area routes?

Accepted Answer

Inter-Area Prefix LSA (Type 0x2003). In OSPFv3, Inter-Area Prefix LSAs (Type 0x2003) are used to advertise prefixes from other areas.

Answer

Network LSA (Type 0x2002)

Answer

Intra-Area Prefix LSA (Type 0x2009)

Answer

Router LSA (Type 0x2001)

Question 19

An ISP is implementing BGP PIC (Prefix Independent Convergence) for edge routers. Which BGP feature must be enabled to support PIC for core-facing failures?

Accepted Answer

BGP additional-paths install. BGP PIC relies on installing a backup path in the FIB. For core-facing failures, BGP Fast External Fallover and BGP PIC with backup paths are used; specifically, 'bgp additional-paths install' is needed to install backup paths.

Answer

BGP deterministic-med

Answer

BGP route refresh

Answer

BGP bestpath as-path multipath-relax

Question 20

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