350-501 Networking Practice Test 15 — 15 Questions

Question 1

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 2

An ISP is deploying BGP confederations to reduce iBGP mesh requirements. Which of the following statements about BGP confederations are true? (Choose two.)

Accepted Answer

The next-hop attribute is unchanged across confederation boundaries. BGP confederations divide an AS into sub-ASes. eBGP-like behavior is used between sub-ASes, but the AS_PATH length calculation treats the confederation as a single AS. The sub-AS number is appended to the AS_PATH with a special type code, but the AS_PATH length for best path selection ignores confederation segments.

Answer

The AS_PATH length calculation includes confederation segments when selecting the best path

Answer

Confederations use a special type of eBGP between sub-ASes, but they retain the IGP metric across the confederation

Answer

The MED attribute is replaced by a confederation-specific metric

Question 3

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 4

An SP engineer is troubleshooting IS-IS routing. The network uses wide metrics, and some links have been configured with TE metrics. Which statement correctly describes the relationship between TE metrics and narrow metrics in IS-IS?

Accepted Answer

Wide metrics allow values up to 2^24 - 1, while narrow metrics allow up to 63.. IS-IS supports both narrow (6-bit) and wide (24-bit) style metrics. TE metrics are separate TLVs that carry additional information for MPLS-TE and do not replace the standard metric used for SPF computation.

Answer

Narrow metrics are used only for L1 routes, while TE metrics are used for L2.

Answer

TE metrics override narrow metrics for SPF calculations.

Answer

TE metrics are used by default when metric-style wide is configured.

Question 5

In an OSPF network, an area is configured as a Not-So-Stubby Area (NSSA). Which statement about LSA types in this area is correct?

Accepted Answer

Type 7 LSAs are originated by ASBR within the NSSA and converted to Type 5 by the ABR.. NSSA areas allow Type 7 LSAs to carry external routes, which are translated to Type 5 at the ABR. Type 5 LSAs are not allowed within the NSSA, and Type 4 LSAs are also blocked. Type 3 LSAs (summary) are allowed.

Answer

Type 1 and Type 2 LSAs are not allowed in NSSA.

Answer

Type 4 LSAs are used to advertise the ABR to other areas.

Answer

Type 5 LSAs are flooded within the NSSA.

Question 6

An SP uses OSPF with Traffic Engineering extensions to support RSVP-TE. Which LSA type is used to carry TE information in OSPF?

Accepted Answer

Type 10 Opaque LSAs.. OSPF TE extensions use Opaque LSAs. Specifically, Type 10 Opaque LSAs (area-scoped) carry TE information as defined in RFC 3630.

Answer

Type 11 Opaque LSAs.

Answer

Type 5 LSAs.

Answer

Type 9 Opaque LSAs.

Question 7

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 8

Which BGP attribute is used to influence inbound traffic to an AS by indicating the preferred path into the AS?

Accepted Answer

MED. The MED (Multi-Exit Discriminator) is used to influence inbound traffic from neighboring ASes. It is advertised to eBGP peers and is compared when multiple paths to the same prefix exist from the same neighboring AS.

Answer

AS_PATH

Answer

LOCAL_PREF

Answer

Weight

Question 9

A service provider is deploying BGP PIC (Prefix Independent Convergence) to improve convergence after a link failure. Which mechanism does BGP PIC leverage to achieve fast failover?

Accepted Answer

It pre-installs a backup path in the routing table and forwarding plane.. BGP PIC uses backup paths that are pre-installed in the RIB/FIB. When the primary path fails, traffic is immediately switched to the backup path without waiting for BGP re-convergence.

Answer

It decreases the BGP update timer to propagate withdrawals faster.

Answer

It reduces the BGP hold timer to detect failures faster.

Answer

It uses BFD to detect failures and triggers BGP to recompute routes immediately.

Question 10

In OSPFv3, which statement correctly describes how OSPFv3 differs from OSPFv2 regarding router IDs and adjacencies?

Accepted Answer

OSPFv3 uses a 32-bit Router ID independent of IPv6 addresses.. OSPFv3 uses a 32-bit Router ID independent of IPv6 addresses. Adjacencies are formed with Router IDs, not link-local addresses. OSPFv3 runs per-link rather than per-subnet.

Answer

OSPFv3 uses the same LSA types as OSPFv2.

Answer

OSPFv3 requires both IPv4 and IPv6 addresses on interfaces.

Answer

OSPFv3 uses IPv6 addresses to form adjacencies.

Question 11

Which BGP community is used to prevent a route from being advertised to any eBGP peers?

Accepted Answer

NO_EXPORT. The well-known community NO_EXPORT (0xFFFFFF01) prevents a route from being advertised to any eBGP peers. The route can still be advertised within the AS.

Answer

INTERNET

Answer

LOCAL_AS

Answer

NO_ADVERTISE

Question 12

An SP is deploying 6VPE (IPv6 L3VPN). Which BGP extensions are used to carry IPv6 VPN prefixes?

Accepted Answer

AFI=2 (IPv6), SAFI=128 with IPv4 next-hop encoded as IPv6-mapped.. 6VPE uses MP-BGP with the IPv6 VPN AFI (AFI=2) and SAFI=128 (MPLS-labeled VPN). The next-hop is an IPv4 address (the PE's loopback) encoded as a mapped IPv6 address, but the VPNv6 address family carries the prefixes.

Answer

AFI=1 (IPv4), SAFI=128 with IPv6 next-hop.

Answer

AFI=2, SAFI=1 (unicast) with MPLS labels.

Answer

AFI=1, SAFI=128 with IPv6 VPN prefixes.

Question 13

Which TWO BGP attributes are considered during the best path selection process and can be used to influence outbound traffic from an AS? (Choose two.)

Accepted Answer

LOCAL_PREF. Weight (Cisco proprietary) and LOCAL_PREF are the first two criteria in BGP path selection. They influence outbound traffic by choosing the preferred path for routes learned from multiple sources.

Answer

NEXT_HOP

Answer

MED

Answer

AS_PATH

Question 14

Which THREE of the following are valid IS-IS TLV types used to support traffic engineering and segment routing? (Choose three.)

Accepted Answer

TLV 22 (Extended IS Reachability). IS-IS TE extensions use various TLVs. TLV 22 (Extended IS Reachability) carries wide metrics and TE information. TLV 135 (Extended IP Reachability) carries IP prefixes with wide metrics. TLV 36 (Prefix SID) is used for segment routing to assign SIDs to prefixes.

Answer

TLV 2 (IS Neighbors)

Answer

TLV 128 (IP Internal Reachability)

Question 15

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