CCNA Spcor Networking Questions — Page 2 of 2

Multi-Selecteasy

A service provider is deploying IS-IS with wide metrics to support traffic engineering. Which two statements about IS-IS wide metrics are correct?

Select 2 answers

A.Wide metrics are required for segment routing.

B.Wide metrics are incompatible with narrow metrics and require a full migration.

C.Wide metrics use TLV 135 for extended IS reachability.

D.Narrow metrics can only be used with L1 routing.

E.Wide metrics support values up to 16,777,215.

AnswersC, E

TLV 135 carries wide metrics for IS-IS.

Why this answer

Wide metrics use a 24-bit or 32-bit field, allowing values up to 16,777,215 or more, and are backward compatible with narrow metrics via apportioning.

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Multi-Selectmedium

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.)

Select 2 answers

A.LOCAL_PREF

B.NEXT_HOP

C.MED

D.AS_PATH

E.Weight

AnswersA, E

Correct. LOCAL_PREF influences outbound traffic within the AS.

Why this answer

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.

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MCQhard

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

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

B.It requires both IPv4 and IPv6 addresses on every router

C.It uses stateless translation between IPv4 and IPv6 at the network edge

D.It tunnels IPv4 packets over IPv6 using GRE

AnswerC

MAP-T uses stateless NAT64-like translation.

Why this answer

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.

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MCQhard

A service provider wants to provide IPv6 connectivity over an MPLS IPv4 core using 6PE. Which BGP extension is required on the provider edge routers?

A.Labeled unicast IPv4 address family

B.VPNv4 address family with route-target extended community

C.IPv6 address family with next-hop encoded as an IPv4-mapped IPv6 address

D.IPv6 address family with next-hop encoded as an IPv6 address

AnswerC

This allows IPv4 next-hop in IPv6 AF.

Why this answer

6PE uses MP-BGP with the IPv6 address family and an IPv4 next-hop (the PE's IPv4 address), encoded via the IPv4-mapped IPv6 address format.

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MCQeasy

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

A.It identifies the system ID of the router.

B.It is always set to 0x00 for the device itself.

C.It is used to select the routing protocol.

D.It identifies the area within the routing domain.

AnswerB

Correct. SEL is 0x00 for the network layer entity.

Why this answer

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.

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MCQhard

In IS-IS, which TLV is used to carry traffic engineering information for MPLS-TE?

A.TLV 135

B.TLV 229

C.TLV 22

D.TLV 128

AnswerA

TLV 135 carries TE extended IP reachability information.

Why this answer

The IS-IS TE Extended IP Reachability TLV (135) carries TE metrics such as bandwidth, admin group, etc., for MPLS-TE.

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Multi-Selectmedium

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

Select 2 answers

A.Standard area

B.Stub area

C.Totally stubby area

D.Backbone area

E.NSSA

AnswersB, E

Stub areas block Type 5 LSAs.

Why this answer

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

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MCQeasy

Which technology allows an IPv6-only customer edge router to connect to an MPLS provider edge router using IPv4 transport, encapsulating IPv6 packets in MPLS with a labeled IPv4 next-hop?

A.6VPE

B.NAT64

C.MAP-T

D.6PE

AnswerD

6PE provides IPv6 over MPLS with IPv4 next-hop.

Why this answer

6PE (IPv6 Provider Edge) uses MP-BGP to exchange IPv6 prefixes with IPv4 next-hop addresses over MPLS. It does not require IPv6 in the core.

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Multi-Selecthard

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

Select 3 answers

A.Customer edge (CE) routers with IPv6 connectivity

B.6rd tunneling

C.MPLS-enabled core network

D.NAT64 translation

E.MP-BGP with IPv6 VPN address family (VPNv6)

AnswersA, C, E

CE routers must support IPv6.

Why this answer

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

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MCQmedium

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

A.OSPF Type 10 Opaque LSA

B.OSPF Type 1 LSA

C.OSPF Type 5 LSA

D.OSPF Type 7 LSA

AnswerA

Type 10 Opaque LSA carries TE information.

Why this answer

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

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MCQmedium

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?

A.To identify the route reflector that reflected the route

B.To indicate the cluster-id of the route reflector

C.To prevent routing loops by ensuring the route is not accepted if the originator-id matches the local router-id

D.To carry the next-hop information for IPv6 prefixes

AnswerC

Correct; if a router receives a route with its own router-id as originator-id, it discards the route.

Why this answer

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.

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Multi-Selecthard

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

Select 3 answers

A.TLV 22 (Extended IS Reachability)

B.TLV 2 (IS Neighbors)

C.TLV 36 (Prefix SID)

D.TLV 135 (Extended IP Reachability)

E.TLV 128 (IP Internal Reachability)

AnswersA, C, D

Correct. Used for TE and wide metrics.

Why this answer

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.

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Multi-Selecthard

A service provider is implementing 6VPE to provide IPv6 L3VPN services. Which three statements about 6VPE are true?

Select 3 answers

A.6VPE supports overlapping IPv6 address spaces between different VPNs.

B.6VPE PE routers must have IPv6 connectivity to the MPLS core.

C.6VPE requires a full IPv6 routing table on the PE router.

D.6VPE uses MP-BGP extensions with AFI 2 (IPv6) and SAFI 128 (MPLS-labeled VPN address family).

E.6VPE encapsulates IPv6 packets using GRE tunnels.

AnswersA, B, D

VRFs separate VPNs, allowing overlapping addresses.

Why this answer

6VPE uses MP-BGP with AFI=2 and SAFI=1 (or 128?) Actually, 6VPE uses AFI=2 (IPv6) and SAFI=1 (unicast) or SAFI=128 (VPN). Standard is SAFI=128 for VPN. It advertises IPv6 prefixes with an MPLS label and VPN label. 6VPE requires dual-stack PE routers.

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MCQmedium

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?

A.Network LSA (Type 0x2002)

B.Intra-Area Prefix LSA (Type 0x2009)

C.Router LSA (Type 0x2001)

D.Inter-Area Prefix LSA (Type 0x2003)

AnswerD

Correct LSA for inter-area prefixes.

Why this answer

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

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MCQmedium

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?

A.TLV 130

B.TLV 22

C.TLV 135

D.TLV 128

AnswerB

TLV 22 (Extended IS reachability) carries TE information including wide metrics.

Why this answer

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.

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MCQmedium

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

A.OSPFv3 uses a 32-bit Router ID independent of IPv6 addresses.

B.OSPFv3 uses the same LSA types as OSPFv2.

C.OSPFv3 requires both IPv4 and IPv6 addresses on interfaces.

D.OSPFv3 uses IPv6 addresses to form adjacencies.

AnswerA

Correct. Router ID is 32-bit and must be configured or derived from an IPv4 address.

Why this answer

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.

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MCQmedium

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

A.Locally originated routes (prefer routes originated by the local router)

B.MED

C.AS_PATH length

D.eBGP over iBGP

AnswerA

Correct; routes originated locally are preferred over received routes.

Why this answer

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.

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MCQeasy

Which IS-IS metric type supports values up to 2^24-1 and is used for traffic engineering?

A.Extended metrics

B.Narrow metrics

C.TE metrics

D.Wide metrics

AnswerD

Wide metrics use 24 bits and support larger values for TE.

Why this answer

IS-IS wide metrics use a 24-bit field, allowing values up to 16,777,215, and are required for TE.

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Multi-Selectmedium

Which TWO of the following are characteristics of IS-IS Partial Route Computation (PRC)? (Choose two.)

Select 2 answers

A.PRC is used when a router's system ID changes.

B.PRC is triggered when a new adjacency is formed.

C.PRC improves convergence by avoiding full SPF runs for prefix changes.

D.PRC recomputes only IP prefixes without recalculating the SPF tree.

E.PRC requires metric-style wide to operate.

AnswersC, D

Correct. PRC reduces CPU load for prefix changes.

Why this answer

PRC is used when only leaf (IP prefix) information changes, not the IS-IS topology. It avoids full SPF recalculation, improving convergence.

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MCQeasy

In IS-IS, which type of router is responsible for exchanging routing information between different areas?

A.L1/L2 router

B.L1 router

C.Attached router

D.L2 router

AnswerD

L2 routers exchange information between areas.

Why this answer

L2 routers handle inter-area routing in IS-IS, while L1 routers handle intra-area routing. L1/L2 routers act as both.

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MCQhard

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

A.It provides fast convergence by pre-installing backup paths in the FIB

B.It reduces the number of BGP updates during a flap

C.It reduces the memory usage on the router

D.It eliminates the need for BFD

AnswerA

Correct; backup paths are precomputed and installed.

Why this answer

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.

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MCQeasy

Which BGP attribute is used to influence inbound traffic to a multi-homed AS by indicating the preferred entry point?

A.AS_PATH

B.COMMUNITY

C.MED

D.LOCAL_PREF

AnswerC

MED influences inbound traffic.

Why this answer

MED (Multi-Exit Discriminator) is used to influence inbound traffic from neighboring ASes by suggesting the preferred path into the AS.

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MCQhard

In an IS-IS network, a service provider wants to achieve fast convergence using Partial Route Computation (PRC). Which of the following events triggers a PRC instead of a full SPF?

A.A router's system ID changes

B.An LSP with a new fragment arrives

C.A new adjacency is formed between two routers

D.An IP prefix is withdrawn from a directly connected network

AnswerD

Correct. A prefix change without topology change triggers PRC.

Why this answer

PRC is triggered when an IP prefix changes (addition, removal, or metric change) without a change in the IS-IS topology (i.e., no change in adjacency or reachable IS-IS neighbors). PRC only recalculates the affected prefixes, avoiding full SPF.

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MCQeasy

Which BGP attribute is used to indicate the preference of a route within an AS and is propagated to iBGP peers but not to eBGP peers by default?

A.WEIGHT

B.LOCAL_PREF

C.MED

D.AS_PATH

AnswerB

Correct. LOCAL_PREF is used for route preference within an AS.

Why this answer

LOCAL_PREF is a well-known discretionary attribute that indicates the degree of preference for a route within an AS. It is sent to iBGP peers but not to eBGP peers by default.

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100

Multi-Selectmedium

Which three BGP attributes are considered during the route selection process before comparing AS_PATH length? (Choose three.)

Select 3 answers

A.LOCAL_PREF

B.Weight

C.NEXT_HOP

D.Locally originated routes

E.MED

AnswersA, B, D

LOCAL_PREF is compared second.

Why this answer

Weight, LOCAL_PREF, and locally originated routes are compared before AS_PATH length in the BGP best path selection algorithm.

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101

Multi-Selectmedium

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.)

Select 2 answers

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

B.MAP-T requires a dedicated IPv6 prefix for each customer

C.MAP-T employs a Border Router that performs translation between IPv4 and IPv6

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

E.MAP-T can operate in stateless mode

AnswersC, E

Correct. The BR performs IPv4-IPv6 translation.

Why this answer

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.

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102

Multi-Selectmedium

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.)

Select 2 answers

A.ORIGINATOR_ID

B.NEXT_HOP

C.LOCAL_PREF

D.AS_PATH

E.CLUSTER_LIST

AnswersA, E

ORIGINATOR_ID prevents loops within a cluster.

Why this answer

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

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103

MCQmedium

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?

A.OSPF Type 7 LSAs

B.OSPF Type 11 Opaque LSAs

C.OSPF Type 10 Opaque LSAs

D.OSPF Type 5 LSAs

AnswerC

Correct. Type 10 Opaque LSAs carry TE information.

Why this answer

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).

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104

MCQhard

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

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

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

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

D.The Designated Router (DR) is elected to reduce the number of adjacencies and LSDB flooding.

AnswerD

DR/BDR reduce O(n^2) to O(n).

Why this answer

OSPFv3 operates similarly to OSPFv2 on broadcast networks, electing a DR and BDR using Hello protocol, and forming adjacencies with the DR.

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105

MCQmedium

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

A.Default metric (TLV 2)

B.Narrow metrics (TLV 128/130)

C.TE metric (TLV 138)

D.Wide metrics (TLV 135/236/22)

AnswerD

Wide metrics use 24-bit fields and support TE.

Why this answer

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

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106

MCQhard

A service provider wants to use BGP Prefix Independent Convergence (PIC) for faster failover. Which BGP feature must be enabled to support PIC?

A.BGP additional paths

B.BGP multipath

C.BGP route reflectors

D.BGP fast external fallover

AnswerA

Additional paths allow backup path installation.

Why this answer

BGP PIC requires BGP additional paths (add-path) or BGP PIC edge, which installs backup paths in the FIB independent of the prefix count.

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107

MCQeasy

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

A.To compute the entire SPF tree after a topology change

B.To recompute only the routes that are affected by a change in IP reachability

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

D.To repair IS-IS adjacency after link failure

AnswerB

PRC is triggered by IP prefix changes.

Why this answer

PRC recomputes only affected routes when a leaf changes, without full SPF, enabling faster convergence.

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108

MCQeasy

Which IS-IS router type maintains a full Layer 2 routing table of all areas and can act as a gateway between areas?

A.Level 2

B.Level 0

C.Level 1/2

D.Level 1

AnswerA

Correct. Level 2 routers maintain the full L2 routing table and route between areas.

Why this answer

In IS-IS, Level 2 routers route between areas and maintain a complete L2 database. Level 1 routers route within an area, and Level 1/2 routers act as both, but the question asks for the type that maintains a full L2 routing table of all areas. Level 2 routers specifically perform inter-area routing.

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109

MCQeasy

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

A.Identifies the application layer protocol

B.Indicates that this is a router (always 0x00)

C.Identifies the area

D.Identifies the system ID

AnswerB

SEL=0x00 indicates the network entity.

Why this answer

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

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110

MCQmedium

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?

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

B.Wide metrics allow values up to 2^24 - 1, while narrow metrics allow up to 63.

C.TE metrics override narrow metrics for SPF calculations.

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

AnswerB

Wide metrics use 24 bits (max 16777215), narrow use 6 bits (max 63).

Why this answer

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.

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111

MCQhard

In BGP, an SP router receives multiple routes to the same prefix. The first route has a weight of 100, LOCAL_PREF of 200, AS_PATH length 3, and is learned via eBGP. The second route has weight 50, LOCAL_PREF 150, AS_PATH length 2, and is learned via iBGP. According to BGP route selection, which route will be preferred?

A.The second route (AS_PATH length 2)

B.The first route (eBGP learned)

C.The second route (LOCAL_PREF 150)

D.The first route (weight 100)

AnswerD

Correct. Weight is checked first; higher weight wins.

Why this answer

BGP selection order: highest weight first. Route 1 has weight 100, Route 2 has weight 50, so Route 1 is preferred regardless of other attributes.

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112

Multi-Selecteasy

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

Select 3 answers

A.MED

B.AS_PATH length

C.eBGP over iBGP

D.Weight

E.LOCAL_PREF

AnswersB, D, E

AS_PATH is fourth after local preference.

Why this answer

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

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113

MCQeasy

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

A.NO_EXPORT

B.INTERNET

C.LOCAL_AS

D.NO_ADVERTISE

AnswerA

Correct. NO_EXPORT prevents advertisement to eBGP peers.

Why this answer

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.

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114

MCQmedium

An SP engineer is designing an OSPF network with several remote sites that should not receive external routes but need to reach external destinations via a default route. Which OSPF area type best meets this requirement while also preventing Type 5 LSAs from entering?

A.NSSA

B.Backbone area 0

C.Stub area

D.Totally stubby area

AnswerD

Correct. Totally stubby area blocks Type 5 and Type 3 LSAs except a default route, so remote sites only have a default route to reach external destinations.

Why this answer

A totally stubby area blocks Type 5 and Type 3 LSAs (except a default route). A stub area blocks Type 5 but allows Type 3 (inter-area routes). An NSSA allows Type 7 LSAs for external routes from the area.

A totally stubby area is the correct choice because it blocks both Type 5 and Type 3 (except default), meeting the requirement.

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115

MCQmedium

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

A.Type 11 Opaque LSAs.

B.Type 10 Opaque LSAs.

C.Type 5 LSAs.

D.Type 9 Opaque LSAs.

AnswerB

Correct. Type 10 Opaque LSAs are area-scoped and carry TE information.

Why this answer

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

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116

Multi-Selectmedium

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.)

Select 2 answers

A.NSSA

B.Totally stubby area

C.Backbone area 0

D.Stub area

E.Normal area

AnswersA, D

NSSA blocks Type 5 but injects Type 7 for external routes.

Why this answer

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

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117

MCQmedium

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

A.To prevent routing loops by ensuring that a route is not reflected back to its originator

B.To indicate the next-hop IP address

C.To identify the route reflector

D.To carry the community value

AnswerA

A router ignores routes with its own ORIGINATOR_ID.

Why this answer

ORIGINATOR_ID is a non-transitive optional attribute that identifies the router that originated the route into the iBGP domain, used to prevent loops.

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118

Multi-Selecthard

An SP network uses OSPFv3 for IPv6 routing. Which three statements about OSPFv3 are true? (Choose three.)

Select 3 answers

A.OSPFv3 requires an IPv4 address on the interface to form adjacencies

B.OSPFv3 uses link-local addresses for next-hop

C.OSPFv3 uses the same LSA types as OSPFv2 but with different formats

D.OSPFv3 uses IPsec for authentication

E.OSPFv3 supports multiple instances per link

AnswersB, C, E

Correct. OSPFv3 uses link-local addresses for next-hop and to form adjacencies.

Why this answer

OSPFv3 runs on a per-link basis, uses link-local addresses for adjacencies, and supports multiple instances per link. OSPFv3 does not require IPv4; it is for IPv6. It uses the same LSA types but with modified formats.

Option D is false because OSPFv3 uses Authentication Trailer for authentication, not IPsec.

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119

MCQmedium

In BGP confederation, how does the AS_PATH attribute handle the confederation sub-AS numbers to prevent loops?

A.Confederation sub-AS numbers are added to the regular AS_PATH

B.Confederation sub-AS numbers are carried in a separate confederation AS_PATH segment and are stripped when routes leave the confederation

C.Confederation sub-AS numbers are replaced by the confederation identifier

D.Confederation sub-AS numbers are ignored for loop detection

AnswerB

Correct. The confederation AS_PATH is used within the confederation and removed when routes are advertised outside.

Why this answer

In BGP confederation, confederation sub-AS numbers are carried in a separate confederation AS_PATH segment and are not visible to external BGP peers. The confederation AS_PATH is used for loop prevention within the confederation, while the regular AS_PATH remains unchanged when routes leave the confederation.

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120

MCQeasy

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?

A.LOCAL_PREF

B.AS_PATH length

C.MED

D.Weight

AnswerC

MED is compared only if the routes are from the same AS; if from different ASs, MED is not compared by default.

Why this answer

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

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121

MCQhard

In OSPF TE extensions for RSVP-TE, which LSA type is used to carry TE information (such as link attributes) in OSPF?

A.Type 11 Opaque LSA

B.Type 5 AS-external LSA

C.Type 10 Opaque LSA

D.Type 9 Opaque LSA

AnswerC

Type 10 Opaque LSA is area-scoped and carries TE information.

Why this answer

Opaque LSA Type 10 (Area-local) is used for TE information in OSPF. Type 9 is link-local, Type 11 is AS-scoped.

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122

MCQmedium

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?

A.Stub area

B.Totally stubby area

C.NSSA

D.Backbone area 0

AnswerC

NSSA allows external routes via Type 7 LSAs.

Why this answer

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

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123

MCQhard

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?

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

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

C.Type 7 LSAs are originated by ASBR within the NSSA and converted to Type 5 by the ABR.

D.Type 5 LSAs are flooded within the NSSA.

AnswerC

Correct. Type 7 LSAs originated in NSSA and translated at ABR to Type 5 for other areas.

Why this answer

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.

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124

MCQhard

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?

A.IPv6 prefixes are transported over an IPv6 MPLS core using LDPv6

B.IPv6 prefixes are carried as VPNv6 prefixes in MP-BGP with an IPv4 next-hop

C.IPv6 prefixes are encapsulated in IPv4 tunnels with GRE

D.IPv6 prefixes are converted to IPv4 using NAT64 before MPLS forwarding

AnswerB

Correct; 6PE uses MP-BGP with AFI=2 (IPv6) and SAFI=1, with next-hop as IPv4 address.

Why this answer

6PE uses BGP to carry IPv6 prefixes 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.

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125

MCQhard

Which OSPF area type is most suitable for a service provider's customer-facing network where external routes are blocked, but internal routes (including inter-area) are allowed, and the area should not accept Type 5 LSAs?

A.NSSA

B.Backbone area

C.Totally stubby area

D.Stub area

AnswerD

Stub area blocks Type 5 LSAs and uses default route.

Why this answer

A stub area blocks Type 5 LSAs but allows inter-area and intra-area routes. It injects a default route. NSSA allows limited external routes via Type 7, which is not desired here.

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