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CCNP Service Provider study materials
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CCNP Service Provider practice questions

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Question 1Service Provider Network Architecture

In a service provider network, which functional layer is responsible for aggregating customer traffic from access nodes and handing it to the core?

  1. Distribution (aggregation) layer Correct answer.
  2. Peering edge layer
  3. Access layer
  4. Core layer

Explanation

The distribution layer aggregates traffic from many access nodes and applies policy before handing it to the core. Access connects individual subscribers, while the core provides high-speed transport between aggregation and edge sites.

Question 2Service Provider Network Architecture

Which IGP is most commonly deployed inside a single service provider point of presence to carry loopback and link addresses?

  1. EIGRP
  2. BGP
  3. OSPF or IS-IS Correct answer.
  4. RIPng

Explanation

Service providers typically run OSPF or IS-IS as the internal IGP to distribute loopback and link addressing within a PoP. BGP carries customer and Internet routes, and RIPng or EIGRP are rarely used at provider scale.

Question 3Service Provider Network Architecture

Which statement best describes the role of an autonomous system number in service provider routing?

  1. It identifies a physical router chassis within a PoP
  2. It defines the OSPF area boundary between PoPs
  3. It uniquely identifies a customer VLAN across the provider network
  4. It identifies a set of routers under one administrative routing policy Correct answer.

Explanation

An AS number identifies a collection of routers administered under a single routing policy and used in BGP path selection. It is not a hardware identifier, an IGP area, or a Layer 2 VLAN tag.

Question 4Service Provider Network Architecture

A provider wants to offer a Layer 3 VPN where each customer's routes are kept separate on PE routers. Which mechanism provides that separation?

  1. Spanning tree per customer
  2. 802.1Q trunking across the core
  3. NAT translation at the PE
  4. VRF instances with route targets Correct answer.

Explanation

VRF instances on PE routers maintain separate routing tables, and route targets control import and export of routes between VRFs. Layer 2 mechanisms and NAT do not provide per-customer Layer 3 route isolation.

Question 5Service Provider Network Architecture

Which protocol is used to signal MPLS label bindings between label switch routers?

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

Explanation

LDP distributes label bindings for IGP-learned prefixes between label switch routers. RSVP-TE signals traffic-engineered LSPs, and PIM handles multicast, so neither replaces basic label distribution.

Question 6Service Provider Network Architecture

What is the primary purpose of a route reflector in a large service provider iBGP design?

  1. To reduce the number of required iBGP sessions by reflecting routes Correct answer.
  2. To eliminate the need for an IGP inside the PoP
  3. To convert iBGP routes into OSPF external routes
  4. To provide MPLS label distribution for the core

Explanation

A route reflector relaxes the full-mesh iBGP requirement by reflecting routes from clients to other clients. It does not replace the IGP, redistribute into OSPF, or distribute MPLS labels.

Question 7Service Provider Network Architecture

In a service provider design, what distinguishes the peering edge from the core layer?

  1. It hosts the DHCP servers for residential subscribers
  2. It provides the high-capacity transport between PoPs
  3. It interconnects with external autonomous systems and enforces external routing policy Correct answer.
  4. It aggregates subscriber access lines into the PoP

Explanation

The peering edge connects the provider to external autonomous systems and applies policy toward peers and transit providers. Aggregation, high-capacity transport, and subscriber services are handled by other layers.

Question 8Service Provider Network Architecture

Which technology allows a provider to carry Layer 2 customer frames across an MPLS core?

  1. BGP route reflection
  2. VPLS or EVPN-based E-LAN Correct answer.
  3. MPLS LDP only
  4. OSPF area 0

Explanation

VPLS and EVPN-based E-LAN services transport Layer 2 frames across an MPLS core by emulating a LAN segment. Route reflection, OSPF, and LDP alone do not provide Layer 2 emulation.

Question 9Service Provider Network Architecture

A provider runs IS-IS with wide metrics and wants traffic to prefer a high-capacity path over a shorter but congested path. Which approach fits?

  1. Advertise the congested path with a lower metric
  2. Increase the IS-IS metric on the congested path Correct answer.
  3. Enable LDP on the congested path only
  4. Reduce the OSPF reference bandwidth

Explanation

Raising the IS-IS metric on the congested path makes the high-capacity path more attractive in shortest-path computation. Lowering the metric on the congested path would have the opposite effect, and LDP or OSPF settings do not apply to an IS-IS design.

Question 10Service Provider Network Architecture

A PE router must import customer routes from only one of several VRFs on the same device. Which configuration element controls this?

  1. The BGP cluster ID
  2. The OSPF area ID of the VRF
  3. The LDP router ID
  4. The route target in the VRF import policy Correct answer.

Explanation

Route targets attached to VPN routes determine which VRFs import them, so the VRF import policy selects the desired customer routes. OSPF area IDs, LDP router IDs, and cluster IDs do not govern VPN route import.

Question 11Service Provider Network Architecture

Why do service providers typically configure BGP next-hop-self on route reflectors toward their clients?

  1. To strip MPLS labels from reflected routes
  2. To ensure clients can resolve the next hop through the IGP without needing the original PE loopback Correct answer.
  3. To force clients to prefer eBGP over iBGP
  4. To convert reflected routes into static routes

Explanation

Next-hop-self makes the route reflector advertise itself as the next hop so clients can resolve it via the IGP even if they lack reachability to the originating PE loopback. It does not change eBGP preference, strip labels, or create static routes.

Question 12Service Provider Network Architecture

A provider wants fast reconvergence after a core link failure without relying on IGP timers alone. Which design technique is most appropriate?

  1. BGP prefix-independent convergence with additional paths Correct answer.
  2. Increasing OSPF hello and dead intervals
  3. Using static routes to all core destinations
  4. Disabling LDP on core links

Explanation

BGP additional paths combined with prefix-independent convergence lets routers precompute and install alternate paths, speeding reconvergence beyond IGP timer tuning. Lengthening IGP timers slows detection, disabling LDP breaks label forwarding, and static routes do not reconverge dynamically.

Question 13Service Provider Network Architecture

Which MPLS transport mechanism provides explicit traffic-engineered paths with bandwidth reservation?

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

Explanation

RSVP-TE signals label-switched paths along explicitly defined routes and can reserve bandwidth for them. LDP follows IGP shortest paths without reservation, BGP-LU distributes labeled routes, and PIM-SSM handles multicast.

Question 14Service Provider Network Architecture

What is the purpose of a sham link in an MPLS Layer 3 VPN with backdoor links between customer sites?

  1. To carry multicast traffic between VRFs
  2. To make the VPN backbone path preferred over the backdoor IGP path Correct answer.
  3. To provide encryption for VPN traffic
  4. To replace route targets between VRFs

Explanation

A sham link creates an intra-area OSPF adjacency across the VPN so the backbone path can be preferred over a lower-cost backdoor link. It is not a multicast, route-target, or encryption mechanism.

Question 15Service Provider Network Architecture

A provider deploys EVPN with a VLAN-based service and wants all-active multihoming on the access side. Which function enables that?

  1. BGP route reflection
  2. Ethernet segment with all-active designated forwarder election Correct answer.
  3. Single-active pseudowire redundancy
  4. OSPF graceful restart

Explanation

EVPN all-active multihoming relies on Ethernet segments and designated forwarder election so multiple PEs can forward for the same segment. Single-active redundancy is the opposite model, while graceful restart and route reflection do not provide access multihoming.

Question 16Service Provider Network Architecture

Which QoS behavior is applied at the provider edge to enforce a committed rate for a customer's traffic class?

  1. Weighted random early detection alone
  2. Priority queueing without a rate limit
  3. Policing with a committed information rate Correct answer.
  4. Traffic shaping to the line rate

Explanation

Policing meters traffic against a committed information rate and marks or drops excess, enforcing the contracted rate at the edge. WRED manages queue depth, priority queueing changes scheduling, and shaping to line rate does not enforce a committed rate.

Question 17Service Provider Network Architecture

In a hierarchical design, why is the core kept simple with few policies and high forwarding capacity?

  1. To terminate subscriber PPP sessions
  2. To host all customer VRFs and route targets
  3. To maximize scalability and predictable latency for aggregated traffic Correct answer.
  4. To apply per-subscriber QoS policies

Explanation

Keeping the core simple with minimal policy and high capacity supports scalability and predictable forwarding for aggregated traffic. Customer VRFs, subscriber termination, and per-subscriber policy belong at the edge or aggregation layers.

Question 18Service Provider Network Architecture

A provider wants to interconnect two autonomous systems it operates while preserving separate routing policies. Which design is appropriate?

  1. A single OSPF area spanning both networks
  2. eBGP between the two AS numbers with policy on each side Correct answer.
  3. Static routes between the two networks
  4. iBGP with a shared route reflector cluster

Explanation

Using distinct AS numbers with eBGP between them preserves separate routing policies and loop prevention. A single IGP area, shared route reflector cluster, or static routes would blur administrative boundaries and scale poorly.

Question 19Service Provider Network Architecture

What is the primary benefit of segment routing over traditional LDP-based MPLS in a provider core?

  1. It removes the need for any label forwarding
  2. It removes the need for per-LSP state in the core by using prefix and adjacency segments Correct answer.
  3. It eliminates the need for an IGP in the core
  4. It replaces BGP for customer route distribution

Explanation

Segment routing encodes paths as lists of prefix or adjacency segments so core routers need not maintain per-LSP state. It still relies on an IGP for segment advertisement and BGP for customer routes, and it still forwards labeled packets.

Question 20Service Provider Network Architecture

A provider offers a Layer 3 VPN and a customer requires that traffic between two sites follow the provider backbone even though a direct link exists. Which combination achieves this?

  1. Sham link plus matching OSPF cost adjustments in the VRF Correct answer.
  2. BGP local preference plus NAT
  3. Route target rewrite plus static routes
  4. LDP plus PIM-SM

Explanation

A sham link creates an intra-area adjacency across the VPN, and adjusting OSPF cost in the VRF makes the backbone path preferred over the backdoor. Route target rewrites, LDP with PIM, and NAT do not control this path selection.

Question 21Service Provider Network Architecture

In an EVPN design, which route type advertises MAC and IP bindings learned from the data plane?

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

Explanation

EVPN Type 2 routes carry MAC and IP address bindings learned from hosts and are central to bridging and ARP suppression. Type 1 advertises Ethernet segment autodiscovery, Type 3 advertises inclusive multicast, and Type 5 carries IP prefixes.

Question 22Service Provider Network Architecture

A provider wants to reduce BGP table size on PE routers by receiving only a default route from its upstream transit providers while still receiving full customer routes. Which approach fits?

  1. Redistribute BGP into OSPF on the PEs
  2. Configure default-originate toward PEs from the route reflector and filter transit prefixes Correct answer.
  3. Use static routes for all customer prefixes
  4. Disable BGP on the PE routers

Explanation

Originating a default route toward PEs while filtering transit prefixes reduces table size on the PEs and preserves customer-specific routes. Disabling BGP, redistributing into OSPF, or using static routes would break customer routing or scale poorly.

Question 23Service Provider Network Architecture

Which design consideration makes an anycast-based service edge resilient across multiple PoPs?

  1. Advertising unique service addresses per PoP with static routes
  2. Using per-PoP OSPF areas with no BGP
  3. Disabling route reflectors at each PoP
  4. Advertising the same service address from multiple PoPs and relying on BGP best-path selection Correct answer.

Explanation

Anycast advertises the same service address from multiple PoPs so BGP best-path selection steers each user to a suitable site and provides automatic failover. Unique addresses, IGP-only designs, and disabling route reflectors do not deliver anycast resilience.

Question 24Service Provider Network Architecture

Which statement accurately describes the relationship between an IGP and BGP in a provider core during a link failure?

  1. The IGP and BGP always reconverge simultaneously
  2. BGP reconverges before the IGP in all cases
  3. BGP does not depend on IGP next-hop reachability in a provider core
  4. The IGP reconverges first and BGP next-hop reachability follows, so BGP may briefly retain stale paths Correct answer.

Explanation

BGP depends on the IGP for next-hop reachability, so IGP reconvergence typically occurs first and BGP then updates its paths, which can leave brief stale entries. They do not reconverge simultaneously, and BGP does depend on IGP reachability.

Question 25Service Provider Network Architecture

A provider plans a large-scale Layer 3 VPN with many VRFs per PE and wants to minimize configuration and routing overhead. Which approach is most appropriate?

  1. Full mesh of VRFs with static routes between all sites
  2. Redistributing all VRFs into a single global table
  3. Route target constraint with per-VRF route targets and BGP VPNv4 route filtering Correct answer.
  4. Disabling route targets and using OSPF alone

Explanation

Route target constraint lets a PE advertise only the route targets it needs, reducing VPN route propagation and memory overhead at scale. Static full mesh, merging VRFs into one table, or removing route targets would break isolation or scale poorly.

Question 26Service Provider Network Architecture

Which functional layer of a service provider network aggregates customer-facing access connections and applies per-customer policy before traffic enters the backbone?

  1. The international transit layer
  2. The aggregation or distribution layer Correct answer.
  3. The internet peering exchange layer
  4. The long-haul core layer

Explanation

The aggregation (distribution) layer sits between access and core, concentrating many customer links and hosting per-customer policy such as QoS marking and filtering. The core is deliberately policy-light and only forwards at high capacity. Transit and peering layers face other autonomous systems, not individual access customers.

Question 27Service Provider Network Architecture

In an MPLS Layer 3 VPN, which router holds the VRF tables and exchanges VPNv4 routes with other provider edge routers?

  1. The customer edge router
  2. The route reflector client at the customer site
  3. The provider core router
  4. The provider edge router Correct answer.

Explanation

The PE router instantiates VRFs, attaches route targets and route distinguishers, and exchanges VPNv4 (or VPNv6) routes with peer PEs over MP-BGP. Core (P) routers only swap labels and never hold customer VRFs. CE routers belong to the customer and run plain IP peering with the PE.

Question 28Service Provider Network Architecture

What does a route distinguisher accomplish in an MPLS Layer 3 VPN?

  1. It makes otherwise identical customer prefixes unique in the provider's MP-BGP table Correct answer.
  2. It authenticates the CE-to-PE BGP session
  3. It defines the label stack depth used between PE routers
  4. It selects which QoS queue the customer prefix uses in the core

Explanation

Overlapping customer address space would collide in a shared BGP table, so the RD is prepended to each prefix to create a unique VPNv4 NLRI. Route targets, not the RD, control which VRFs import the route. The RD carries no forwarding or QoS meaning.

Question 29Service Provider Network Architecture

Which protocol is most commonly used as the IGP inside a large service provider core because it scales well with many nodes and supports flexible TLV extension?

  1. OSPFv2 with many areas
  2. RIPv2
  3. IS-IS Correct answer.
  4. EIGRP

Explanation

IS-IS runs directly on the link layer, scales to large flat topologies, and is easily extended through TLVs, which is why providers favor it in the core. RIPv2 has a hop limit of 15 and cannot serve a provider backbone. EIGRP is largely a Cisco enterprise protocol and rarely chosen for multi-vendor provider cores.

Question 30Service Provider Network Architecture

Which BGP attribute is used by default to select the best path among routes learned from different neighboring autonomous systems?

  1. Origin type
  2. AS_PATH length Correct answer.
  3. MED
  4. LOCAL_PREF

Explanation

After weight and LOCAL_PREF (which apply within the local AS), the shortest AS_PATH is the first attribute that compares routes from different autonomous systems. MED is evaluated later and only among paths from the same neighbor AS by default. Origin type comes after AS_PATH in the decision process.

Question 31Service Provider Network Architecture

What is the role of the route target extended community in an MPLS Layer 3 VPN?

  1. It determines the BGP router ID of the PE
  2. It sets the MPLS label value assigned to the prefix
  3. It controls which VRFs import and export a given VPN route Correct answer.
  4. It identifies the physical interface toward the customer

Explanation

Route targets are extended communities attached on export and matched by import policy, so they define VPN membership independently of the RD. The RD only guarantees uniqueness of the NLRI. Labels and router IDs are unrelated to route targets.

Question 32Service Provider Network Architecture

In segment routing over MPLS, what does a node segment (prefix-SID) represent?

  1. A label reserved for RSVP-TE bandwidth reservation
  2. A label that identifies a customer VRF on the egress PE
  3. A locally significant label used only for the last hop before the CE
  4. A globally significant label that steers traffic along the shortest path to a specific router Correct answer.

Explanation

A prefix-SID is advertised by the IGP and maps to a globally understood index, so any ingress router can steer a packet to that node along the IGP shortest path. It is not VRF-scoped and does not require per-flow signaling. Local and adjacency labels serve different purposes.

Question 33Service Provider Network Architecture

Which device type in an MPLS network performs label swapping based on the incoming label without maintaining customer routing information?

  1. The provider (P) router Correct answer.
  2. The customer edge (CE) router
  3. The provider edge (PE) router
  4. The route reflector

Explanation

P routers switch labeled packets using the incoming label and an LFIB entry, and they hold only the global routing table. PEs hold VRF and VPNv4 state, and CEs hold only customer routes. A route reflector is a BGP control-plane role, not a forwarding element defined by label-only switching.

Question 34Service Provider Network Architecture

A provider wants its PE routers to learn customer routes from a CE that is managed by the customer and uses static routing. Which design approach keeps the provider's IGP free of customer prefixes?

  1. Configure the static routes as summary routes in the global table on P routers
  2. Redistribute the static routes into the provider IS-IS core
  3. Redistribute the static routes into MP-BGP as VPNv4 routes on the PE Correct answer.
  4. Advertise the static routes into the core with a low IS-IS metric

Explanation

Customer prefixes belong in the VPN address family, so the PE should inject static routes into MP-BGP with the appropriate route target. Leaking them into the core IGP would inflate the backbone table and expose customer addressing. P routers must not carry customer state at all.

Question 35Service Provider Network Architecture

A provider runs BGP between two of its own autonomous systems and wants traffic from AS 65001 to prefer a specific exit point into AS 65002. Which mechanism gives deterministic control without relying on AS_PATH manipulation?

  1. Prepend the AS number on the preferred path
  2. Lower the MED sent to AS 65002
  3. Apply a higher LOCAL_PREF on the preferred egress path within AS 65001 Correct answer.
  4. Increase the weight on the backup path

Explanation

LOCAL_PREF is the standard tool for choosing an outbound exit within a single autonomous system and is evaluated before AS_PATH. Prepending on the preferred path would make it less attractive, which is backwards. MED influences inbound traffic from the other AS and is not honored consistently across providers.

Question 36Service Provider Network Architecture

A provider's PE routers peer with many CEs, and the provider wants to avoid a full mesh of iBGP sessions among PEs. Which design element reduces the session count while preserving route distribution?

  1. Route reflectors placed in the core or at a dedicated control-plane tier Correct answer.
  2. Additional physical links between every pair of PEs
  3. Static routes between all PE loopbacks
  4. A full mesh of eBGP sessions between PEs

Explanation

Route reflectors concentrate iBGP sessions so each PE needs only a session to its reflector rather than to every other PE. Adding links between all PEs increases cost without solving the control-plane scaling problem. eBGP between PEs in the same AS is not the normal design, and static routes cannot distribute VPNv4 reachability.

Question 37Service Provider Network Architecture

A provider offers a Layer 2 VPN and a customer requires that the provider network never see the customer's IP addressing. Which service model fits this requirement?

  1. A Layer 3 VPN with the customer routes in a VRF
  2. A point-to-point or multipoint Layer 2 service carried over the MPLS core Correct answer.
  3. An internet transit service with public addressing
  4. A managed CE service with provider-owned IP addressing

Explanation

A Layer 2 service transports customer frames transparently, so the provider never inspects or stores customer IP routes. A Layer 3 VPN requires the PE to hold customer prefixes in a VRF, which is exactly what the customer wants to avoid. Internet transit and managed CE designs also involve provider-visible IP routing.

Question 38Service Provider Network Architecture

An ISP wants to receive only a default route from one upstream transit provider while still receiving full tables from another. Which BGP design element implements this per-neighbor policy?

  1. A lower LOCAL_PREF on all routes from the first neighbor
  2. A larger MED value advertised to the first neighbor
  3. An outbound prefix list applied toward the first neighbor
  4. An inbound route filter on the first neighbor that permits only the default route Correct answer.

Explanation

Inbound filtering controls exactly which prefixes are accepted from a given neighbor, so permitting only 0.0.0.0/0 achieves the goal. LOCAL_PREF affects path selection among accepted routes but does not reduce table size. Outbound filters and MED affect what the neighbor receives, not what the local router stores.

Question 39Service Provider Network Architecture

A provider wants fast failure detection on core links so that IGP reconvergence begins within milliseconds rather than waiting for hello timers to expire. Which mechanism is designed for this?

  1. Bidirectional Forwarding Detection with a short interval Correct answer.
  2. Enabling BGP graceful restart
  3. Raising the IGP hold timer
  4. Increasing the IGP hello interval

Explanation

BFD provides sub-second failure detection independent of the routing protocol timers and notifies the IGP immediately. Lengthening hello or hold timers slows detection. Graceful restart helps during planned control-plane restarts and does not speed up failure detection.

Question 40Service Provider Network Architecture

A provider deploys EVPN for a Layer 2 service and needs to prevent loops while allowing all-active multihoming on the access side. Which EVPN capability supports this?

  1. Ethernet segment with designated forwarder election and aliasing Correct answer.
  2. BGP add-path for the EVPN address family
  3. Route type 3 inclusive multicast per VLAN
  4. Route type 5 IP prefix advertisement

Explanation

An Ethernet segment groups the multihomed links, and designated forwarder election prevents duplicate flooded frames while aliasing lets the PE use all links for known unicast. Inclusive multicast routes handle BUM delivery but do not themselves prevent loops. IP prefix routes serve Layer 3 service, and add-path is a scaling feature.

Question 41Service Provider Network Architecture

A provider's core uses IS-IS with traffic engineering extensions, and the design team wants label-switched paths with reserved bandwidth for a small set of premium flows. Which technology matches this requirement?

  1. LDP signaled LSPs
  2. RSVP-TE signaled LSPs Correct answer.
  3. Static MPLS label bindings
  4. BGP labeled unicast only

Explanation

RSVP-TE carries explicit route objects and bandwidth reservations, which is what premium traffic-engineered paths require. LDP follows the IGP shortest path with no reservation capability. Static bindings and labeled unicast distribute labels but provide no bandwidth reservation.

Question 42Service Provider Network Architecture

Two customer sites connect to the same provider Layer 3 VPN and also have a backdoor link between them that the customer wants used only as a backup. Which design element ensures the provider path is preferred?

  1. A sham link between the two PEs to carry the VPN route over the backbone Correct answer.
  2. A higher MED on the provider path
  3. An eBGP multihop session between the CE routers
  4. A static route on each CE pointing to the backdoor

Explanation

Without a sham link, the CE-to-CE backdoor route is preferred because it appears as an intra-area or shorter path. The sham link creates a virtual link across the MPLS backbone so the VPN route competes on equal terms and can be preferred. Static routes toward the backdoor would defeat the goal.

Question 43Service Provider Network Architecture

A provider wants to offer a service where a single anycast IP address is reachable in several PoPs and user traffic lands on the nearest one. Which design condition is essential for this to work reliably?

  1. The PoPs exchange the address through a full iBGP mesh only
  2. Each PoP advertises the address with a different AS_PATH length
  3. The address is only advertised from one PoP at a time
  4. The service is identical and stateless or state-synchronized in every PoP advertising the address Correct answer.

Explanation

Anycast relies on every location being able to serve the same request, so the service must be identical and either stateless or synchronized across PoPs. Differing AS_PATH lengths would bias all traffic to one site rather than the nearest. Advertising from one PoP at a time is the opposite of anycast.

Question 44Service Provider Network Architecture

A provider's core IGP and BGP are both running, and a core link fails. Which statement best describes the expected interaction?

  1. BGP keeps the failed path until the hold timer expires and the IGP waits for BGP
  2. BGP reconverges first and then the IGP updates its topology
  3. The IGP and BGP reconverge simultaneously with no ordering
  4. The IGP reconverges first and BGP next hops follow, so BGP withdraws or replaces paths that depended on the failed link Correct answer.

Explanation

BGP depends on IGP reachability of next hops, so IGP convergence precedes BGP path changes. Once the next hop becomes unreachable, BGP withdraws or replaces affected paths. There is a dependency ordering rather than simultaneous independent convergence.

Question 45Service Provider Network Architecture

A provider's design team is comparing a flat IGP domain with a hierarchical IGP. Which outcome argues in favor of a hierarchical design?

  1. Smaller link-state databases and faster SPF in each area Correct answer.
  2. Guaranteed bandwidth reservation on all core links
  3. Elimination of the need for BGP in the core
  4. Automatic encryption of IGP adjacencies

Explanation

Area or level boundaries limit the scope of topology changes and shrink each router's link-state database, which speeds SPF. Hierarchy does not remove the need for BGP between domains or autonomous systems. Bandwidth reservation and adjacency encryption are separate features unrelated to hierarchy.

Question 46Service Provider Network Architecture

A provider must connect a new regional PoP to the backbone and wants the regional IGP to remain isolated from the national core IGP while still exchanging customer VPN routes. Which design achieves this?

  1. Redistribute regional IGP routes into the national core IGP
  2. Run a separate IGP in the region and exchange VPNv4 routes with the core over MP-BGP between regional and core PEs Correct answer.
  3. Use static routes between the regional and core PEs for all customer prefixes
  4. Extend the national core IGP into the regional PoP with the same area or level

Explanation

Keeping separate IGPs and stitching them with MP-BGP preserves isolation while still distributing VPN routes with route targets. Extending or redistributing the core IGP into the region would merge the topologies and expose regional instability to the core. Static routes cannot carry VPNv4 NLRI.

Question 47Service Provider Network Architecture

A provider plans a large Layer 3 VPN with many VRFs per PE and wants to reduce the number of route targets and import policies that must be maintained. Which design technique addresses this?

  1. Assigning a unique route target to every VRF
  2. Grouping VRFs into VPN communities that share a small set of route targets Correct answer.
  3. Advertising every VRF prefix into the global routing table
  4. Using a unique route distinguisher per prefix instead of per VRF

Explanation

Shared route targets within a VPN community let many VRFs import and export with a small, consistent policy set, which reduces operational overhead. Unique route targets per VRF multiply the policy to maintain. Per-prefix RDs and leaking prefixes into the global table add complexity and risk.

Question 48Service Provider Network Architecture

A provider's PE routers receive full internet tables from two upstreams and full VPNv4 tables from route reflectors. Which design change best reduces memory pressure on the PEs while preserving customer VPN service?

  1. Remove the route reflectors and build a full iBGP mesh
  2. Advertise the internet table into the core IGP
  3. Move internet table handling to dedicated border routers and keep PEs focused on VPNv4 Correct answer.
  4. Disable MP-BGP on the PEs and use static VRF routes

Explanation

Separating the internet-facing role from the VPN PE role keeps large global tables on dedicated border routers and lets PEs carry only what the VPN service needs. Removing reflectors increases session count without reducing table size. Disabling MP-BGP or leaking the internet table into the IGP would break the service.

Question 49Service Provider Network Architecture

A provider wants traffic engineering across its core without maintaining per-LSP state in every core router. Which approach aligns best with this constraint?

  1. Static label bindings configured on every core router
  2. LDP with per-destination label allocation only
  3. RSVP-TE with a full mesh of signaled LSPs between all PE pairs
  4. Segment routing with a controller computing explicit segment lists at the ingress Correct answer.

Explanation

Segment routing keeps per-path state at the ingress as a segment list, so core routers only forward based on the top segment and hold no per-LSP state. A full mesh of RSVP-TE LSPs creates significant signaling state in the core. Static bindings and plain LDP do not provide traffic-engineered paths.

Question 50Service Provider Network Architecture

A provider operates a Layer 3 VPN where two customer sites use the same private address range in different VRFs. Which statement explains why the provider can forward both correctly?

  1. The route distinguisher makes the VPNv4 NLRIs unique, and the per-VRF label on the egress PE disambiguates the forwarding Correct answer.
  2. The core IGP carries both prefixes with different metrics
  3. The provider rewrites customer addresses at the ingress PE using NAT
  4. The CE routers negotiate which site owns the address

Explanation

Overlapping prefixes are made unique in BGP by the RD, and the egress PE assigns a distinct VPN label per VRF so the receiving PE can forward into the correct VRF. NAT is not required for address separation in an MPLS VPN. The core IGP never carries customer prefixes, and CEs do not arbitrate address ownership.