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Cisco SPCOR 350-501 practice questions

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First 50 of 199 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

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Question 1Architecture

A service provider wants a single control-plane protocol that distributes both IPv4 and IPv6 customer routes across its core while keeping each address family's policy independent. Which design meets this requirement?

  1. Static routes redistributed into IS-IS Level 1
  2. MP-BGP with separate address-family configurations for IPv4 and IPv6 Correct answer.
  3. RIPv2 with dual-stack route redistribution
  4. OSPFv2 with IPv6 extensions enabled globally

Explanation

Multiprotocol BGP carries multiple address families over one TCP session, and each address family is configured and policed separately with its own activate, network, and route-policy statements. This lets a provider apply distinct import and export policy to IPv4 and IPv6 customer prefixes.

Question 2Architecture

Which statement describes the role of a P router in a service provider MPLS core?

  1. It terminates IPsec tunnels from enterprise sites
  2. It forwards labeled packets and does not maintain customer VPN routing tables Correct answer.
  3. It terminates all customer VRFs and advertises them into BGP
  4. It performs route reflection for all provider edge routers

Explanation

Provider (P) routers switch MPLS labeled packets across the core and only hold the global routing table plus label bindings. Customer VPN routes live in VRFs on PE routers, so P routers stay free of customer routing state.

Question 3Architecture

Which technology allows an enterprise to keep its own routing domain while the service provider transports its routes transparently across the provider core?

  1. Layer 3 MPLS VPN Correct answer.
  2. VPLS
  3. Transparent LAN service
  4. Cisco SD-WAN

Explanation

A Layer 3 MPLS VPN lets the provider carry customer routes in per-VRF tables separated by route targets, so the enterprise keeps control of its own routing domain. The provider forwards customer packets based on labels rather than participating in the customer's IGP.

Question 4Architecture

Which protocol is used to signal MPLS label bindings for traffic-engineered LSPs in a service provider core?

  1. BGP-LU
  2. LDP
  3. RSVP-TE Correct answer.
  4. PIM-SM

Explanation

RSVP-TE reserves bandwidth along an explicit path and distributes labels for traffic-engineered LSPs. LDP distributes labels for IGP-derived paths but does not signal bandwidth reservations or explicit paths.

Question 5Architecture

Which QoS model classifies and marks traffic at the network edge and then applies per-hop behaviors based on those markings in the core?

  1. Differentiated Services Correct answer.
  2. Integrated Services
  3. Weighted fair queueing
  4. Best-effort forwarding

Explanation

Differentiated Services (DiffServ) marks packets with a DSCP at the edge and lets each core hop apply a per-hop behavior keyed to that marking. This scales because core routers do not maintain per-flow state.

Question 6Architecture

Which Cisco platform provides centralized policy and a distributed data plane for large-scale service provider routing while running IOS XR?

  1. Cisco Catalyst 9200 Series
  2. Cisco Nexus 1000V
  3. Cisco ASR 9000 Series Correct answer.
  4. Cisco Meraki MX Series

Explanation

The Cisco ASR 9000 Series is a service provider edge and aggregation platform that runs IOS XR with a distributed forwarding architecture. It is designed for high-scale MPLS, VPN, and subscriber services.

Question 7Architecture

What is the primary purpose of a route target in an MPLS Layer 3 VPN?

  1. To identify the customer VRF into which a VPN route is imported Correct answer.
  2. To authenticate BGP sessions between PE routers
  3. To determine the IGP metric for the PE loopback
  4. To select the label stack used for forwarding

Explanation

Route targets are extended BGP communities attached to VPN routes that control import into and export from VRFs. A PE imports a route only when its VRF is configured with a matching import target.

Question 8Architecture

Which routing protocol is commonly used as the provider core IGP because it supports fast convergence and traffic engineering extensions?

  1. IS-IS Correct answer.
  2. RIPv2
  3. BGP
  4. EIGRP

Explanation

IS-IS is widely deployed as a service provider core IGP because it scales well, converges quickly, and carries traffic engineering extensions. It runs directly over Layer 2 and avoids the IP dependency that OSPF has.

Question 9Architecture

A PE router receives a VPNv4 route with a route target that no local VRF imports. What happens to that route?

  1. It is dropped and not installed in any local VRF Correct answer.
  2. It is converted into an IPv4 static route
  3. It is installed in the global routing table
  4. It is reflected to all other PE routers

Explanation

Route target import policy determines whether a VPNv4 route enters a local VRF. If no VRF imports the attached route target, the route is not installed anywhere on that PE.

Question 10Architecture

Which mechanism allows a PE router to advertise a single label for all routes in a VRF, reducing label consumption?

  1. Per-VRF label allocation Correct answer.
  2. Per-nexthop label allocation
  3. Per-interface label allocation
  4. Per-prefix label allocation

Explanation

Per-VRF label allocation assigns one label to the whole VRF so the egress PE forwards based on the label and then performs a VRF lookup. This conserves label space on platforms with large VRF and prefix counts.

Question 11Architecture

An engineer needs to verify that a PE is receiving VPNv4 prefixes from a route reflector. Which command shows the VPNv4 address family state?

  1. show bgp vpnv4 unicast summary Correct answer.
  2. show mpls ldp neighbor
  3. show ip route vrf all
  4. show isis neighbor

Explanation

The show bgp vpnv4 unicast summary command reports the VPNv4 address family neighbor state and prefix counts. It is the direct way to confirm that VPNv4 sessions are established and exchanging routes.

Question 12Architecture

Which design consideration drives the choice of a BGP route reflector cluster in a large service provider network?

  1. Replacing MPLS forwarding with IP forwarding
  2. Reducing the number of full-mesh iBGP sessions between PE routers Correct answer.
  3. Removing the need for route targets
  4. Eliminating the need for an IGP in the core

Explanation

Route reflectors reduce the full-mesh iBGP requirement by reflecting routes to clients within a cluster. This keeps BGP session counts manageable as the number of PE routers grows.

Question 13Architecture

Which statement best describes the function of a pseudowire in a service provider network?

  1. It provides a Layer 3 VPN routing instance
  2. It encrypts customer traffic end to end
  3. It distributes labels for IPv4 prefixes
  4. It emulates a Layer 2 service across an MPLS or IP packet-switched network Correct answer.

Explanation

A pseudowire carries Layer 2 frames across a packet-switched network by encapsulating them and emulating the attachment circuit. This enables services such as Ethernet over MPLS without native Layer 2 transport.

Question 14Architecture

Which feature allows a service provider to offer a Layer 2 multipoint Ethernet service while maintaining per-customer separation in the MPLS core?

  1. MVPN
  2. L3VPN
  3. VPLS Correct answer.
  4. 6PE

Explanation

VPLS provides multipoint Layer 2 Ethernet emulation over MPLS, with each customer service separated by a unique VPLS instance. It lets the provider offer a bridged LAN-like service across sites.

Question 15Architecture

Which tool should an engineer use to validate that a new route policy will not inadvertently filter a customer prefix before applying it to a production BGP session?

  1. Apply the policy to a lab session and compare advertisements Correct answer.
  2. show running-config | include route-map
  3. show ip bgp summary
  4. show route-map

Explanation

Testing a route policy in a controlled session and comparing the resulting advertisements confirms its behavior before it affects production. Viewing configuration alone does not prove which prefixes the policy permits.

Question 16Architecture

Which element of a service provider architecture is responsible for applying subscriber policy and service activation at the edge?

  1. The route reflector
  2. The provider edge service router Correct answer.
  3. The provider core P router
  4. The customer premises router

Explanation

The provider edge service router terminates customer access and applies subscriber policy, service activation, and QoS treatment at the edge. Core P routers only transport traffic between edges.

Question 17Architecture

Which protocol extension allows BGP to carry IPv6 routes across an IPv4 MPLS core without configuring IPv6 on the core routers?

  1. NAT64
  2. DS-Lite
  3. 6PE Correct answer.
  4. 6VPE

Explanation

6PE uses IPv4-mapped IPv6 next hops and labels so PE routers can forward IPv6 traffic over an IPv4 MPLS core. The core routers only need IPv4 and MPLS, not IPv6 routing.

Question 18Architecture

A provider wants to offer differentiated treatment for voice, video, and best-effort traffic across its core. Which approach applies the correct per-hop behavior?

  1. Use only FIFO queueing on all core interfaces
  2. Mark all traffic with the same DSCP and rely on link bandwidth
  3. Mark traffic with DSCP at the edge and configure matching queueing policies in the core Correct answer.
  4. Apply classification only on customer premises equipment

Explanation

DiffServ relies on consistent DSCP marking at the edge and matching per-hop behaviors such as priority queueing in the core. Voice and video need low-latency treatment while best-effort traffic uses remaining capacity.

Question 19Architecture

Which Cisco IOS XR feature allows a single physical interface to carry multiple logical routing instances with separate forwarding tables?

  1. PIM sparse mode
  2. MPLS LDP
  3. BGP confederation
  4. VRF-lite with subinterfaces Correct answer.

Explanation

VRF-lite with subinterfaces lets one physical interface carry multiple logical interfaces, each bound to a separate VRF and forwarding table. This supports per-customer or per-service separation without MPLS.

Question 20Architecture

A provider is designing a solution where customer multicast traffic must be carried across an MPLS core. Which architecture addresses this requirement?

  1. 6PE
  2. MVPN Correct answer.
  3. VPLS
  4. LDP

Explanation

Multicast VPN (MVPN) extends customer multicast domains across an MPLS provider core using multicast distribution trees. VPLS and 6PE address Layer 2 and IPv6 unicast transport, not multicast replication.

Question 21Architecture

An engineer observes that a PE router is advertising VPNv4 routes with the correct route target, but the remote PE does not install them. Which is the most likely cause?

  1. The remote VRF lacks a matching import route target Correct answer.
  2. The PE loopbacks are not reachable by the IGP
  3. The core routers are not running LDP
  4. The remote PE has no BGP session to the route reflector

Explanation

If the route arrives but is not installed, the mismatch is usually in import policy, such as a missing or incorrect import route target on the destination VRF. Reachability and session problems would prevent the route from arriving at all.

Question 22Architecture

Which design choice best supports fast convergence in a large MPLS core when a core link fails?

  1. Increasing BGP keepalive timers on all PE sessions
  2. Tuning IGP timers and enabling LDP synchronization with the IGP Correct answer.
  3. Disabling MPLS on all core links
  4. Using static routes for all PE loopbacks

Explanation

Fast convergence requires rapid IGP detection and consistent label bindings, so tuned IGP timers plus LDP-IGP synchronization avoid black holes during reconvergence. Longer BGP timers or static loopback routes would slow or prevent recovery.

Question 23Architecture

A provider is comparing per-prefix and per-VRF label allocation for a PE with thousands of VRFs and millions of prefixes. Which consideration favors per-VRF allocation?

  1. It reduces label space consumption at the cost of an extra VRF lookup at the egress PE Correct answer.
  2. It eliminates the need for route targets
  3. It removes the need for an MPLS core
  4. It guarantees faster convergence than per-prefix allocation

Explanation

Per-VRF allocation uses one label per VRF instead of one per prefix, greatly reducing label consumption when prefix counts are high. The trade-off is an additional VRF lookup on the egress PE after the label is popped.

Question 24Architecture

Which combination best describes how a provider separates customer traffic at both the control plane and the data plane in an L3VPN?

  1. VLANs for control-plane separation and IPsec for data-plane separation
  2. Route reflectors for control-plane separation and VRF-lite for data-plane separation
  3. VRFs with route targets for control-plane separation and MPLS labels for data-plane separation Correct answer.
  4. BGP confederations for control-plane separation and GRE for data-plane separation

Explanation

In an L3VPN, VRFs and route targets keep customer routing tables separate in the control plane. MPLS labels provide the corresponding data-plane separation by directing packets to the correct egress VRF.

Question 25Architecture

A provider needs to carry IPv6 customer VPN traffic over an MPLS core while keeping per-customer separation. Which architecture should be selected?

  1. ISATAP
  2. 6PE
  3. 6VPE Correct answer.
  4. NAT64

Explanation

6VPE combines IPv6 routing with MPLS VPN VRFs so each customer's IPv6 traffic is separated by route targets and labels. Plain 6PE provides global IPv6 reachability without per-customer VPN separation.

Question 26Architecture

In an MPLS Layer 3 VPN, which field in the VPNv4 NLRI carries the Route Distinguisher that makes a customer prefix unique across the provider?

  1. The MP-BGP extended community length field
  2. The BGP Originator ID attribute
  3. The MPLS bottom-of-stack bit
  4. The 8-byte RD prepended to the IPv4 prefix Correct answer.

Explanation

The VPNv4 NLRI is formed by an 8-byte Route Distinguisher followed by the IPv4 prefix, so the same customer address can exist in multiple VRFs without collision. The RD is a local identifier used only for uniqueness and does not by itself control import or export of routes.

Question 27Architecture

A provider uses Segment Routing over an MPLS core with SR-IS-IS. What is the primary purpose of a Prefix-SID in this design?

  1. To advertise the SRGB range to BGP peers
  2. To assign a globally unique loopback address to each router
  3. To bind an MPLS label to a router's prefix so traffic follows the shortest path to it Correct answer.
  4. To identify the egress PE for a VPN service label

Explanation

A Prefix-SID associates an index (and therefore an MPLS label from the SRGB) with an IGP prefix, letting routers forward traffic along the shortest path to that prefix using segment routing. It is distributed by the IGP, not BGP, and is distinct from service labels used for VPNs.

Question 28Architecture

An engineer must design an L2VPN service that provides point-to-point Ethernet connectivity between two customer sites over an MPLS core without running a routing protocol on the customer edge. Which architecture fits this requirement most directly?

  1. A VPLS instance with a full mesh of pseudowires
  2. An EVPN instance using IP-VRF route targets
  3. A Layer 3 VPN with static routes on the CE
  4. A point-to-point VPWS pseudowire with AToM Correct answer.

Explanation

A VPWS (Virtual Private Wire Service) using AToM provides a point-to-point Ethernet pseudowire between two attachment circuits, so the CE devices see a transparent Ethernet link and need no routing protocol. It is the simplest fit when only two sites must be connected.

Question 29Architecture

A service provider wants to protect against a PE router failure for a Layer 3 VPN service. Which design approach provides the most direct redundancy for customer VPN connectivity?

  1. Dual-homing the CE to two PEs with redundant VRFs and matching route targets Correct answer.
  2. Configuring BFD on the core links only
  3. Using a single PE with redundant route processors
  4. Increasing the BGP hold timer on the PE-CE session

Explanation

Dual-homing the CE to two PEs, each with a VRF importing the same route targets, allows the customer to retain VPN connectivity if one PE fails. The CE can use a routing protocol or first-hop redundancy to select the active path.

Question 30Architecture

A provider deploys an MPLS core with RSVP-TE tunnels for traffic engineering. An engineer notices that a new tunnel follows the constrained path but bypasses a link that has ample bandwidth. Which factor is the most likely cause when CSPF computes the path?

  1. The link's MPLS MTU is larger than the tunnel MTU
  2. The link's IGP metric is higher than the TE metric threshold
  3. The link lacks a BGP next-hop reachability entry
  4. The link is excluded because its reservable bandwidth is below the tunnel's signaled bandwidth Correct answer.

Explanation

CSPF prunes links whose unreserved bandwidth cannot satisfy the tunnel's requested bandwidth, even if the link is otherwise up and has capacity in aggregate. The tunnel is then signaled along the next shortest feasible path.

Question 31Networking

In Cisco IOS XR, which command enables an IS-IS process and enters the IS-IS configuration submode for the instance named CORE?

  1. router isis instance CORE
  2. router isis CORE Correct answer.
  3. ip router isis CORE
  4. isis instance CORE

Explanation

IOS XR creates an IS-IS routing process with the global command router isis followed by the process/instance name, which then places the CLI into the IS-IS configuration submode. The instance name is a local identifier and does not have to match a NET, though it is commonly aligned with the area design for readability.

Question 32Networking

Which statement correctly describes the role of a NET (Network Entity Title) on an IS-IS router?

  1. It is the NSAP address that identifies the router, with the last byte set to 0x00 as the system ID selector. Correct answer.
  2. It is the BGP router ID redistributed into IS-IS LSPs.
  3. It is the MPLS label used for the IS-IS segment routing prefix-SID.
  4. It is the IPv4 loopback address advertised in the LSP as the router identifier.

Explanation

A NET is an NSAP whose final byte (the NSEL) is 00, meaning the device itself is the destination rather than a transport-layer entity. The system ID portion must be unique within the area and is typically derived from a loopback or MAC address, while the area ID must match for Level 1 adjacency.

Question 33Networking

An engineer must configure OSPFv2 process 10 on IOS XR to run in area 0 on GigabitEthernet0/0/0/1. Which command sequence is valid?

  1. router ospf 10 / interface GigabitEthernet0/0/0/1 / area 0 Correct answer.
  2. ospf 10 / area 0 / interface GigabitEthernet0/0/0/1
  3. router ospf 10 / network 0.0.0.0 255.255.255.255 area 0
  4. router ospf 10 / area 0 / interface GigabitEthernet0/0/0/1

Explanation

IOS XR uses the interface command model: under router ospf, you enter the interface, then assign it to an area. There is no network statement under IOS XR OSPF, which is a key difference from classic IOS configuration.

Question 34Networking

Which BGP path attribute is used by a router to break ties between routes learned from different autonomous systems when all earlier attributes are equal?

  1. ORIGIN
  2. MULTI_EXIT_DISC
  3. LOCAL_PREF
  4. AS_PATH length Correct answer.

Explanation

The BGP best-path algorithm compares weight, LOCAL_PREF, locally originated routes, AS_PATH length, ORIGIN, MED, eBGP over iBGP, and finally router ID. AS_PATH length is compared before MED, so it breaks ties between routes from different ASes (and between routes generally) before MULTI_EXIT_DISC is examined.

Question 35Networking

Which MPLS label range is reserved for static and special-purpose labels such as the implicit null label?

  1. 1048576 and above
  2. 1024 through 1048575
  3. 0 through 15 Correct answer.
  4. 16 through 1023

Explanation

Labels 0 through 15 are reserved by IANA for special purposes, including IPv4 explicit null (0), router alert (1), IPv6 explicit null (2), and implicit null (3). Dynamically assigned labels come from the range starting at 16, with 16-1023 reserved for static assignments by some vendors.

Question 36Networking

What is the purpose of the MPLS experimental (EXP) bits in the label stack entry?

  1. They encode the time-to-live for the label stack.
  2. They indicate whether the bottom-of-stack bit is set.
  3. They identify the label distribution protocol in use.
  4. They carry the Quality of Service treatment for the labeled packet. Correct answer.

Explanation

The 3-bit EXP field (now often called Traffic Class) is used to carry QoS marking across the MPLS domain, typically mapped from IP DSCP or set by a policy. It allows per-hop behavior to be applied without inspecting the encapsulated IP header.

Question 37Networking

Which protocol does Cisco SD-WAN use to distribute fabric routing and policy information among controllers and edge devices?

  1. OSPFv3
  2. BGP
  3. OVSDB
  4. LISP Correct answer.

Explanation

Cisco SD-WAN uses LISP for the control plane to register and resolve endpoint and TLOC information between WAN edges and the controllers. OVSDB is used for the data plane tunnel state between edges, while BGP is used at the service side for routing.

Question 38Networking

A network engineer needs to verify that an LDP session with a peer is fully operational on an IOS XR router. Which command output shows the session state as Oper?

  1. show mpls interfaces
  2. show mpls forwarding
  3. show mpls ldp bindings
  4. show mpls ldp neighbor Correct answer.

Explanation

The show mpls ldp neighbor command displays each LDP peer, its transport address, and the session state, which should read Oper when the session is established. The bindings command shows label-to-prefix mappings, forwarding shows the LFIB, and interfaces shows which interfaces have LDP enabled.

Question 39Networking

In segment routing with MPLS, what does an adjacency SID represent?

  1. A local label that forwards traffic over a specific link to a specific neighbor. Correct answer.
  2. A label bound to a BGP next hop for VPN traffic.
  3. A label used only for RSVP-TE reservation.
  4. A global label that identifies a prefix in the IGP.

Explanation

An adjacency SID is locally significant to the advertising node and steers traffic out a particular adjacency, which is useful for traffic engineering and TI-LFA repair paths. A prefix SID, by contrast, is globally unique within the SR domain and identifies a destination prefix.

Question 40Networking

A router running IS-IS has interfaces in both Level 1 and Level 2. Which LSP types does it generate by default?

  1. Only Level 2 LSPs.
  2. Only Level 1 LSPs unless wide metrics are enabled.
  3. Both Level 1 and Level 2 LSPs. Correct answer.
  4. Only Level 1 LSPs.

Explanation

A router with at least one Level 1 adjacency and one Level 2 adjacency generates separate LSPs for each level, and it sets the ATT bit in its Level 1 LSP to signal a path to other areas. Level 1-only or Level 2-only routers generate only the corresponding LSP type.

Question 41Networking

An engineer configures OSPFv3 on an IOS XR router and notices that no adjacencies form on a point-to-point link. Which configuration element is required for OSPFv3 to operate on that interface?

  1. An IPv4 address on the interface.
  2. A global IPv6 address only.
  3. An OSPFv3 network statement.
  4. A link-local IPv6 address, which is enabled automatically when IPv6 is configured on the interface. Correct answer.

Explanation

OSPFv3 uses IPv6 link-local addresses to form adjacencies, and IOS XR enables link-local addressing automatically when IPv6 is configured on an interface. Global addresses are not required for adjacency formation, and IOS XR does not use network statements for OSPFv3.

Question 42Networking

Which configuration step is required on a PE router to make a VRF participate in MP-BGP VPNv4 route exchange?

  1. Enable LDP on the CE-facing interface.
  2. Redistribute the VRF into OSPF and rely on OSPF to carry VPN labels.
  3. Configure a route target only on the CE router.
  4. Configure a route distinguisher for the VRF and activate the VPNv4 address family toward the peer. Correct answer.

Explanation

The VRF must have a route distinguisher so that overlapping customer prefixes become unique VPNv4 prefixes, and the VPNv4 address family must be activated toward the peer. Route targets control import and export of those prefixes into VRFs, while LDP provides the transport label, not the VPN label.

Question 43Networking

A network uses BGP route reflectors. What is the primary reason for deploying route reflectors instead of a full iBGP mesh?

  1. They convert iBGP routes into eBGP routes to improve path selection.
  2. They reduce the number of required iBGP sessions by relaying routes to clients. Correct answer.
  3. They remove the need for unique router IDs.
  4. They eliminate the need for an IGP inside the AS.

Explanation

Route reflectors relax the iBGP split-horizon rule by reflecting routes learned from one client to other clients and non-clients, replacing the n(n-1)/2 session requirement of a full mesh. They still require an underlying IGP for next-hop reachability and unique router IDs.

Question 44Networking

Which statement about PIM Sparse Mode (PIM-SM) is correct?

  1. It requires no rendezvous point because it uses source-based flooding.
  2. It only supports directly connected receivers.
  3. It floods multicast traffic to all routers in the domain regardless of receivers.
  4. It builds a shared tree rooted at the rendezvous point and can switch to a source-specific shortest-path tree. Correct answer.

Explanation

PIM-SM initially builds a shared (*,G) tree rooted at the RP and then, once traffic arrives, can switch to the shortest-path (S,G) tree for efficiency. This contrasts with PIM Dense Mode, which floods and prunes.

Question 45Networking

Which QoS mechanism in MPLS networks allows a router to mark the EXP bits of a labeled packet based on the incoming IP DSCP value?

  1. The mpls ldp explicit-null command.
  2. A policy map applied with the service-policy command on the interface. Correct answer.
  3. The ip ospf cost command.
  4. The mpls traffic-eng tunnels command.

Explanation

A QoS policy map applied to the interface can classify traffic by DSCP and set the MPLS experimental bits (set mpls experimental imposition) so that the marking is preserved across the label-switched path. The other commands affect label signaling, traffic engineering, or IGP metrics, not QoS marking.

Question 46Networking

A Cisco SD-WAN administrator wants to ensure that voice traffic uses the MPLS transport and falls back to broadband only if latency exceeds a threshold. Which feature implements this?

  1. BGP route reflection within the overlay.
  2. Application-aware routing with an SLA-based policy. Correct answer.
  3. QoS shaping on the service-side interface.
  4. Static route redistribution into OMP.

Explanation

Application-aware routing uses SLA thresholds (latency, loss, jitter) to select the best tunnel per application and to fail over when the primary path degrades. Static redistribution, route reflection, and shaping do not provide per-application path selection based on measured SLA.

Question 47Networking

Which OSPF LSA type is generated by an ASBR to describe routes external to the OSPF domain, and is flooded throughout the AS (except stub areas)?

  1. Type 2
  2. Type 3
  3. Type 5 Correct answer.
  4. Type 1

Explanation

Type 5 AS-external LSAs are originated by ASBRs and flooded to all areas except stub, totally stubby, and NSSA areas, where external information is blocked or carried as type 7. Type 1 and 2 describe intra-area topology, and type 3 describes inter-area prefixes.

Question 48Networking

Which BGP feature is used to prevent a route learned from an iBGP peer from being advertised back to another iBGP peer?

  1. The MED attribute.
  2. The iBGP split-horizon rule, addressed by route reflectors or confederations. Correct answer.
  3. The ORIGIN attribute.
  4. The NEXT_HOP attribute.

Explanation

By default, an iBGP speaker does not advertise routes learned from one iBGP peer to another iBGP peer, which prevents routing loops within the AS. Route reflectors and confederations are the standard mechanisms to relax this rule while preserving loop prevention.

Question 49Networking

Which statement about TI-LFA in segment routing is correct?

  1. It computes a backup path using a post-convergence loop-free alternative with segment list repair. Correct answer.
  2. It requires RSVP-TE to reserve backup bandwidth.
  3. It only works in IS-IS networks.
  4. It replaces the need for any IGP.

Explanation

TI-LFA (Topology-Independent Loop-Free Alternate) computes a repair path based on post-convergence SPF and encodes it as a segment list, providing fast protection for any topology. It works with both IS-IS and OSPF and does not require RSVP-TE.

Question 50Networking

A service provider wants to provide Layer 2 VPN connectivity between two sites using BGP-signaled pseudowires over an MPLS core. Which technology should be used?

  1. MPLS VPNv4 with VRF-lite
  2. Ethernet over MPLS using BGP auto-discovery and LDP signaling Correct answer.
  3. VPLS with LDP signaling only
  4. GRE tunnels with IPsec

Explanation

EoMPLS pseudowires can use BGP for auto-discovery and LDP for signaling the pseudowire label, giving a scalable Layer 2 VPN. VPLS with LDP only lacks the BGP auto-discovery benefit, and VPNv4 is a Layer 3 solution.