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CNPLE practice questions

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Question 1Network Architecture and Design

In a hierarchical campus network design, which layer is primarily responsible for connecting end-user devices and providing port density and PoE access?

  1. WAN edge layer
  2. Distribution layer
  3. Core layer
  4. Access layer Correct answer.

Explanation

The access layer is where end hosts attach to the network, so it provides physical port density, Power over Ethernet, and first-hop connectivity to user devices. It aggregates traffic upward toward distribution switches.

Question 2Network Architecture and Design

What is the primary purpose of the distribution layer in a three-tier network design?

  1. Aggregating access switches and applying routing and policy between them Correct answer.
  2. Transporting traffic at the highest possible speed with no policy
  3. Terminating internet VPN tunnels from remote workers
  4. Providing direct PoE connectivity to desktop phones

Explanation

The distribution layer sits between access and core, aggregating access-layer uplinks while performing inter-VLAN routing, route summarization, and policy enforcement. This keeps complex policy out of the high-speed core.

Question 3Network Architecture and Design

A designer wants to reduce the size of routing tables in the core by advertising a single summary route from each distribution block. Which technique accomplishes this?

  1. Spanning Tree root placement at the core
  2. Route summarization at the distribution layer Correct answer.
  3. Policy-based routing at the core
  4. Static default routing at each access switch

Explanation

Route summarization lets a distribution block advertise one aggregate prefix that covers all its subnets, shrinking core routing tables and limiting topology-change propagation. It requires contiguous addressing so the summary accurately represents the covered networks.

Question 4Network Architecture and Design

Which statement best describes the benefit of a spine-leaf architecture in a data center?

  1. Spines connect only to each other to form a collapsed core
  2. Leaves are daisy-chained to reduce cabling and port count
  3. Every leaf connects to every spine, giving predictable equal-cost paths between hosts Correct answer.
  4. Leaves connect in a ring so each host has a single deterministic path

Explanation

In a spine-leaf fabric, each leaf uplinks to every spine, so any host-to-host flow traverses exactly one spine hop and equal-cost multipathing provides predictable, uniform latency. This uniform diameter also simplifies scaling by adding spines or leaves.

Question 5Network Architecture and Design

In a classic two-tier design, what does 'collapsed core' mean?

  1. The access and distribution functions are combined into one layer
  2. Two separate core switches are stacked into a single logical unit
  3. The core is removed entirely and access switches route directly
  4. The core and distribution functions are combined into one layer Correct answer.

Explanation

A collapsed core merges the distribution and core roles into a single tier of switches, which suits smaller networks where a dedicated core is unnecessary. Access switches still connect upward to this combined layer.

Question 6Network Architecture and Design

Which address block is reserved for private use and is commonly used for internal enterprise addressing?

  1. 10.0.0.0/8 Correct answer.
  2. 172.15.0.0/16
  3. 192.0.2.0/24
  4. 224.0.0.0/4

Explanation

RFC 1918 defines 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 as private address space for internal use. These ranges are not globally routable and require NAT for internet access.

Question 7Network Architecture and Design

A subnet mask of 255.255.255.192 is applied to a network. How many usable host addresses does each subnet provide?

  1. 126
  2. 64
  3. 62 Correct answer.
  4. 30

Explanation

The mask 255.255.255.192 leaves 6 host bits (/26), giving 64 total addresses per subnet. Subtracting the network and broadcast addresses leaves 62 usable host addresses.

Question 8Network Architecture and Design

An engineer must divide 192.168.10.0/24 into four equal subnets. What prefix length results?

  1. /26 Correct answer.
  2. /28
  3. /27
  4. /25

Explanation

Borrowing two host bits from a /24 creates four subnets, each with prefix length /26. Each /26 subnet contains 64 addresses with 62 usable hosts.

Question 9Network Architecture and Design

Which VLSM allocation best conserves address space for a point-to-point WAN link between two routers?

  1. A /22 subnet
  2. A /30 subnet Correct answer.
  3. A /24 subnet
  4. A /28 subnet

Explanation

A point-to-point link needs only two host addresses, and a /30 provides exactly two usable addresses, conserving space. Larger prefixes waste addresses that could serve other segments.

Question 10Network Architecture and Design

What is the primary function of a first-hop redundancy protocol such as VRRP?

  1. Providing a shared virtual gateway address so hosts keep connectivity if one router fails Correct answer.
  2. Preventing Layer 2 loops by blocking redundant ports
  3. Distributing VLAN information between switches
  4. Load-balancing traffic across multiple equal-cost Layer 3 paths

Explanation

First-hop redundancy protocols present a virtual IP and MAC shared by two or more routers, so hosts use a single default gateway that survives a router failure. The active router forwards while the standby takes over if the active fails.

Question 11Network Architecture and Design

Which protocol provides loop-free Layer 2 forwarding by placing redundant ports into a blocking state?

  1. LACP
  2. OSPF
  3. Spanning Tree Protocol Correct answer.
  4. HSRP

Explanation

Spanning Tree Protocol elects a root bridge and blocks redundant paths so the Layer 2 topology remains loop-free. If an active link fails, a blocked port can transition to forwarding to restore connectivity.

Question 12Network Architecture and Design

An access switch connects to two distribution switches, and the designer wants both uplinks active simultaneously for bandwidth. Which technology enables this without a Layer 2 loop?

  1. Static routing with equal costs
  2. VRRP with preemption
  3. Spanning Tree blocking one uplink
  4. Link aggregation using LACP Correct answer.

Explanation

Link aggregation bundles parallel links into one logical channel, so both uplinks forward traffic while the bundle is treated as a single link for loop prevention. LACP negotiates and maintains the bundle between peers.

Question 13Network Architecture and Design

What is the main purpose of a DMZ in a network security architecture?

  1. Extending VLANs between data centers for Layer 2 adjacency
  2. Providing a backup path for core routing convergence
  3. Caching web content to reduce WAN bandwidth
  4. Hosting externally reachable services in a segmented zone isolated from the internal network Correct answer.

Explanation

A DMZ places internet-facing servers in a separate segment with controlled access to both the internet and the internal network. If a public-facing host is compromised, the segmentation limits lateral movement into internal systems.

Question 14Network Architecture and Design

A design requires that guest wireless clients reach the internet but never reach internal corporate subnets. Which approach best enforces this?

  1. Assigning guest clients addresses from the corporate server VLAN
  2. Placing guest traffic in a dedicated VLAN with firewall policy restricting access to internal ranges Correct answer.
  3. Using the same VLAN as employees but with different SSID names
  4. Relying on client-side firewall software on guest devices

Explanation

Isolating guest traffic in its own VLAN lets a firewall or ACL enforce that only internet-bound traffic is permitted while internal ranges are blocked. Segmentation plus explicit policy is far more reliable than trusting endpoint software.

Question 15Network Architecture and Design

Which WAN technology provides a logical full-mesh topology by using a provider network to replicate broadcast and multicast reachability between sites?

  1. GRE tunnel over the internet
  2. Point-to-point leased line
  3. Layer 2 bridging over dark fiber
  4. Layer 3 MPLS VPN Correct answer.

Explanation

An MPLS Layer 3 VPN lets the provider carry customer routes across a shared backbone, giving any-to-any connectivity equivalent to a logical full mesh. Each site peers only with the provider edge, simplifying customer design.

Question 16Network Architecture and Design

What does an SD-WAN overlay primarily use to steer application traffic across multiple underlay transports?

  1. Static routes configured identically on every branch router
  2. Centralized policy applied to encrypted tunnels over each transport Correct answer.
  3. Spanning Tree topology changes propagated to the WAN
  4. Manual VLAN trunking between provider edge devices

Explanation

SD-WAN builds encrypted tunnels over each available transport and applies centrally defined application policies to choose paths based on performance or preference. This decouples forwarding decisions from the physical underlay.

Question 17Network Architecture and Design

A company needs a site-to-site connection that is encrypted over the public internet without a provider SLA. Which design fits best?

  1. A point-to-point leased line between the sites
  2. An IPsec VPN tunnel between the two site firewalls Correct answer.
  3. A Layer 2 transparent LAN service from the provider
  4. A dedicated MPLS Layer 3 VPN from the carrier

Explanation

An IPsec VPN runs encrypted tunnels over ordinary internet connectivity, meeting the encryption requirement without depending on a carrier-managed service. It trades guaranteed performance for flexibility and lower cost.

Question 18Network Architecture and Design

Which IPv6 address type is used for one-to-many delivery to the nearest group members, similar to IPv4 multicast?

  1. Multicast Correct answer.
  2. Unicast
  3. Link-local unicast
  4. Anycast

Explanation

IPv6 multicast delivers a packet to all interfaces that have joined a given group, mirroring IPv4 multicast behavior. IPv6 has no broadcast address; multicast serves the functions broadcast once provided.

Question 19Network Architecture and Design

A designer is planning dual-stack deployment. Which statement correctly describes dual-stack operation?

  1. Hosts translate IPv6 to IPv4 at the network card
  2. IPv6 is disabled until IPv4 addresses are exhausted
  3. Routers tunnel all IPv6 inside IPv4 automatically without configuration
  4. Interfaces run IPv4 and IPv6 simultaneously, and applications choose per destination Correct answer.

Explanation

Dual-stack means an interface is configured with both IPv4 and IPv6 addresses and both protocols are active at once. Applications select the appropriate family based on the destination and name resolution results.

Question 20Network Architecture and Design

Which OSPF design consideration reduces the impact of topology changes on a large area?

  1. Placing all routers in area 0 to avoid inter-area routes
  2. Using multiple areas with summarization at area borders
  3. Disabling hello packets on backbone links
  4. Keeping the topology within a single area to limit summarization Correct answer.

Explanation

Multiple areas confine detailed topology to each area, and area border routers summarize between areas, so a change in one area does not force recalculation everywhere. This is the standard scalability benefit of OSPF area design.

Question 21Network Architecture and Design

A network uses HSRP with two routers sharing a virtual IP. Hosts report intermittent gateway unreachability during failover. Which design change most directly shortens the outage?

  1. Tuning HSRP timers and enabling preemption with a defined priority Correct answer.
  2. Replacing HSRP with static default routes on hosts
  3. Adding a second virtual IP to the standby router
  4. Moving the virtual IP onto the standby router permanently

Explanation

Failover duration depends on hello and hold timers plus which router is preferred, so tuning timers and controlling preemption shortens the period with no active forwarder. Static routes on hosts would remove redundancy entirely.

Question 22Network Architecture and Design

An engineer must choose between a routed access layer and a Layer 2 access layer with a large VLAN spanning many switches. Which consideration favors routed access?

  1. It eliminates the need for any routing protocol
  2. It requires a single large VLAN across all access switches
  3. It increases the size of each broadcast domain for simpler addressing
  4. It contains broadcast domains at each switch and reduces spanning-tree scope Correct answer.

Explanation

Routed access terminates Layer 2 at each access switch, so broadcast domains stay small and spanning tree no longer spans the whole campus. Routing between segments replaces large flat VLANs, improving convergence and stability.

Question 23Network Architecture and Design

What is the primary role of a route reflector in a large BGP deployment?

  1. Encrypting BGP sessions between autonomous systems
  2. Redistributing routes among clients so a full iBGP mesh is unnecessary Correct answer.
  3. Converting external BGP routes into OSPF summaries
  4. Providing first-hop gateway redundancy for hosts

Explanation

A route reflector receives routes from its clients and reflects them to other clients, removing the requirement for every iBGP speaker to peer with every other. This scales iBGP by reducing session count while preserving loop prevention via cluster and originator identifiers.

Question 24Network Architecture and Design

Which design principle best supports high availability at the network core?

  1. Spanning Tree blocking all but one core uplink
  2. Redundant devices and links with fast convergence and no single point of failure Correct answer.
  3. Static routes on all core devices with no dynamic protocol
  4. A single high-capacity core switch to simplify management

Explanation

High availability requires removing single points of failure through redundant hardware and paths, plus fast convergence so traffic reroutes quickly after a failure. A single device or a single active path defeats that goal.

Question 25Network Architecture and Design

A branch office has 40 users, a single WAN link, and no local IT staff. Which design choice is most appropriate?

  1. A full three-tier design with dedicated core and distribution chassis
  2. A data-center-grade leaf pair with dual-homed servers
  3. A spine-leaf fabric with multiple spines for redundancy
  4. A small stack of access switches with a collapsed core and a single router for the WAN Correct answer.

Explanation

A small branch with limited users and one WAN link is best served by a compact design that combines core and distribution functions, avoiding the cost and complexity of extra tiers. Redundancy should match the business requirement and the single-link reality.

Question 26Network Architecture and Design

In a three-tier hierarchical network model, which layer is responsible for policy enforcement, routing between VLANs, and aggregation of access-layer uplinks?

  1. Core layer
  2. Edge layer
  3. Distribution layer Correct answer.
  4. Access layer

Explanation

The distribution layer sits between access and core and is where routing decisions, filtering policies, and summarization are applied to traffic from access switches. The access layer only provides endpoint attachment, and the core layer is optimized for fast transport rather than policy.

Question 27Network Architecture and Design

Which statement describes the role of the collapsed core in a two-tier design?

  1. It combines distribution and core functions in one layer Correct answer.
  2. It separates routing from switching entirely
  3. It removes the need for any redundancy
  4. It places all endpoints on a single flat segment

Explanation

A collapsed core design merges the distribution and core layers into a single tier, which is common in smaller campuses where full three-tier separation adds cost without benefit. Access switches still connect upward to this combined layer, so hierarchy is preserved but compressed.

Question 28Network Architecture and Design

A designer is selecting a topology for a campus with strict requirements for predictable latency and simple troubleshooting. Which topology provides a single, deterministic path between any two nodes?

  1. Partial mesh
  2. Hub and spoke Correct answer.
  3. Full mesh
  4. Ring

Explanation

A hub-and-spoke topology forces every path to traverse the hub, so the path between any two endpoints is predictable and easy to trace. Full and partial mesh introduce multiple paths and more complex forwarding decisions, while a ring provides two directions that require loop-prevention logic.

Question 29Network Architecture and Design

An engineer must summarize four contiguous subnets, 10.1.0.0/24 through 10.1.3.0/24, into a single route. Which summary is correct?

  1. 10.1.0.0/23
  2. 10.1.0.0/24
  3. 10.1.0.0/21
  4. 10.1.0.0/22 Correct answer.

Explanation

Four /24 networks occupy four consecutive third-octet values, which is a block of 4, and a block of 4 corresponds to a /22 mask. The summary must align on the correct boundary, so 10.1.0.0/22 covers 10.1.0.0 through 10.1.3.255.

Question 30Network Architecture and Design

A network design must support 500 hosts in one broadcast domain while keeping broadcast traffic contained. Which approach best meets both goals?

  1. Place all hosts in one VLAN with a /23 subnet
  2. Split hosts into multiple VLANs with one subnet per VLAN Correct answer.
  3. Bridge all access switches into one flat domain
  4. Use a single VLAN with a /16 subnet mask

Explanation

Broadcast domains scale poorly when too many hosts share a single VLAN, so segmenting into multiple VLANs with matching subnets contains broadcast traffic and keeps each domain manageable. A single large VLAN or flat bridged domain increases broadcast overhead and fault scope.

Question 31Network Architecture and Design

A designer wants routing devices to forward traffic for a subnet even when the directly connected interface fails, provided an alternate path exists. Which design element accomplishes this?

  1. A static default route on each router
  2. A dynamic routing protocol with converged alternate paths Correct answer.
  3. Larger subnet masks on the affected links
  4. Proxy ARP enabled on all interfaces

Explanation

Dynamic routing protocols detect topology changes and reconverge onto alternate paths, allowing traffic to be forwarded even after a directly connected link fails. Static defaults do not adapt to failures, and proxy ARP or mask changes do not provide path redundancy.

Question 32Network Architecture and Design

Which design practice improves convergence in a large Layer 2 domain while preserving redundancy?

  1. Limiting the Layer 2 domain size and using routed links between blocks Correct answer.
  2. Increasing the number of VLANs on each trunk without limit
  3. Adding more switches in a single chain
  4. Disabling all redundant links to avoid loops

Explanation

Keeping Layer 2 domains small and connecting blocks with routed links limits the scope of topology changes and speeds convergence. Large bridged domains increase spanning-tree complexity and slow recovery after failures.

Question 33Network Architecture and Design

A company wants a design where management, user, and server traffic are separated so that a compromise in one area does not directly expose the others. Which design principle is being applied?

  1. Any-to-any connectivity
  2. Segmentation by function Correct answer.
  3. Single shared VLAN
  4. Flat network design

Explanation

Segmentation by function places management, user, and server traffic into distinct zones with controlled inter-zone policy, limiting the blast radius of a compromise. Flat or any-to-any designs remove those boundaries and allow unrestricted lateral movement.

Question 34Network Architecture and Design

An engineer must connect two data centers so that either site can serve traffic if the other fails, while keeping the Layer 2 failure domain local to each site. Which design best fits?

  1. Bridge both sites with a single spanning-tree domain
  2. Stretch one VLAN across both sites
  3. Use a routed Layer 3 interconnection between sites Correct answer.
  4. Extend all VLANs over a single trunk between sites

Explanation

A routed Layer 3 interconnection between sites allows each data center to keep its own Layer 2 domain, so a failure in one site does not propagate broadcast storms or spanning-tree instability to the other. Stretching VLANs or bridging sites expands the failure domain and complicates convergence.

Question 35Network Architecture and Design

A design team must choose between a modular architecture and a bespoke point-to-point design for a growing enterprise. Which argument most strongly favors the modular approach?

  1. It eliminates the need for documentation
  2. It guarantees zero downtime during upgrades
  3. It removes the need for routing protocols
  4. It allows each module to scale and change independently Correct answer.

Explanation

Modular architectures divide the network into functional blocks that can grow, be redesigned, or fail independently, which limits change impact and simplifies capacity planning. No architecture eliminates documentation, guarantees zero downtime, or removes the need for routing.

Question 36Network Architecture and Design

A network architect is evaluating a spine-leaf fabric for a data center. Which characteristic makes this design well suited to east-west traffic?

  1. Leaves connect only to a single spine for simplicity
  2. Every leaf connects to every spine, giving equal-cost paths Correct answer.
  3. All servers share one VLAN across the fabric
  4. Spines connect directly to each other in a ring

Explanation

In a spine-leaf fabric each leaf uplinks to every spine, so any leaf-to-leaf flow has multiple equal-cost paths and consistent latency. This predictable any-to-any reachability suits the heavy server-to-server traffic typical of modern data centers.

Question 37Routing and Switching

Which destination address does a switch use to build its MAC address table by default?

  1. The port VLAN identifier of the ingress port
  2. The source MAC address of each incoming frame Correct answer.
  3. The destination MAC address of each incoming frame
  4. The IP address in the frame header

Explanation

A Layer 2 switch learns by examining the source MAC address of every frame that arrives on a port, then records that address together with the ingress port and a timestamp. The destination address is used for forwarding decisions, not for learning. Aging removes stale entries after a configured period.

Question 38Routing and Switching

What is the default administrative distance of a static route on a Cisco router?

  1. 90
  2. 110
  3. 120
  4. 1 Correct answer.

Explanation

Cisco assigns a static route an administrative distance of 1, making it more trustworthy than any dynamically learned route except connected and local interfaces. This value can be changed by appending an AD to the ip route command. Lower AD values are always preferred when multiple sources offer the same prefix.

Question 39Routing and Switching

Which statement describes the purpose of the spanning-tree root bridge election?

  1. It determines which VLAN will carry management traffic
  2. It elects the router that will advertise the default route
  3. It chooses the port with the highest path cost to forward traffic
  4. It selects the switch with the lowest bridge ID as the logical center of the topology Correct answer.

Explanation

All switches in a spanning-tree domain exchange BPDUs and elect a single root bridge based on the lowest bridge ID, which combines priority and MAC address. The root bridge then serves as the reference point for calculating loop-free paths. All ports on the root bridge are designated and forwarding.

Question 40Routing and Switching

A router receives two routes to 10.1.1.0/24: one via OSPF with metric 20 and one via EIGRP with metric 1000. Which route is installed in the routing table?

  1. The OSPF route because its metric is lower
  2. The EIGRP route because its administrative distance is lower Correct answer.
  3. The OSPF route because it was learned first
  4. The EIGRP route because its metric is higher

Explanation

Administrative distance is compared before metrics when routes come from different sources. EIGRP internal routes have an AD of 90, while OSPF has 110, so the EIGRP route wins even though its metric is numerically larger. Metrics from different protocols are not comparable.

Question 41Routing and Switching

Which address range is reserved for link-local IPv6 addresses?

  1. 2000::/3
  2. FF00::/8
  3. FE80::/10 Correct answer.
  4. FC00::/7

Explanation

Link-local IPv6 addresses always begin with the FE80::/10 prefix and are automatically configured on every IPv6-enabled interface. They are used for neighbor discovery and next-hop resolution and are never routed beyond the local link.

Question 42Routing and Switching

What does a router do with a packet whose destination address matches no entry in its routing table and no default route exists?

  1. It floods the packet out all interfaces
  2. It holds the packet until a route appears
  3. It forwards the packet to the lowest-metric neighbor
  4. It drops the packet and returns an unreachable message Correct answer.

Explanation

Without a matching prefix or default route, the router has no forwarding path and discards the packet. It typically generates an ICMP destination unreachable message toward the source. This behavior is part of the classless forwarding process.

Question 43Routing and Switching

Which protocol provides first-hop redundancy by sharing a virtual IP and MAC address among routers?

  1. HSRP Correct answer.
  2. LACP
  3. VTP
  4. STP

Explanation

Hot Standby Router Protocol lets multiple routers present a single virtual IP and virtual MAC to hosts, with one active and others standing by. If the active router fails, a standby takes over the virtual addresses. VRRP provides a similar function in multivendor environments.

Question 44Routing and Switching

Which interface state indicates that a switch port is receiving BPDUs and participating in spanning tree but not forwarding user traffic?

  1. Down
  2. Blocking Correct answer.
  3. Forwarding
  4. Err-disabled

Explanation

A blocking port still receives and processes BPDUs so it can detect topology changes, but it does not forward data frames. This state breaks the Layer 2 loop while keeping the port ready to transition if the topology changes. Forwarding ports actively carry user traffic.

Question 45Routing and Switching

A switch port configured with a voice VLAN receives an untagged frame. How is that frame classified by default?

  1. Into the native VLAN of a trunk
  2. It is dropped as untagged
  3. Into the voice VLAN
  4. Into the access VLAN Correct answer.

Explanation

On a port with both an access VLAN and a voice VLAN, untagged traffic is assigned to the access VLAN while tagged traffic matching the voice VLAN ID goes to the voice VLAN. The phone tags its own traffic, so PC traffic arriving untagged stays in the data VLAN. This separation keeps voice and data traffic distinct.

Question 46Routing and Switching

Which OSPF packet type is used to confirm that a neighbor received a link-state update?

  1. Database Description
  2. Hello
  3. Link-State Request
  4. Link-State Acknowledgment Correct answer.

Explanation

When a router sends a link-state update, the neighbor replies with a link-state acknowledgment listing the LSAs received. This reliable flooding mechanism ensures LSAs are not retransmitted unnecessarily. Requests and database descriptions are used during database synchronization instead.

Question 47Routing and Switching

Which EIGRP packet type is sent to establish neighbor adjacencies and requires acknowledgment?

  1. Update
  2. Reply
  3. Query
  4. Hello Correct answer.

Explanation

EIGRP hello packets are multicast every five seconds on most link types to discover and maintain neighbors. On most media they are sent unreliably, but on multipoint and frame relay interfaces they are acknowledged. Neighbors that stop receiving hellos within the hold time are declared down.

Question 48Routing and Switching

A trunk link carries VLANs 10, 20, and 30, but VLAN 20 is missing from the allowed list on one side. What is the result for VLAN 20 traffic?

  1. VLAN 20 frames are dropped across the trunk Correct answer.
  2. VLAN 20 frames are forwarded untagged
  3. VLAN 20 frames are forwarded with tag 20
  4. VLAN 20 frames are translated to the native VLAN

Explanation

The allowed VLAN list acts as a filter: a frame tagged for a VLAN not permitted on the trunk is discarded. The mismatch must be corrected on both ends for that VLAN to pass. Other allowed VLANs continue to forward normally.

Question 49Routing and Switching

Which feature allows a router interface to be divided into multiple logical subinterfaces, each on a separate VLAN?

  1. Port security
  2. EtherChannel
  3. Private VLAN
  4. Router-on-a-stick Correct answer.

Explanation

Router-on-a-stick configures a single physical interface with subinterfaces, each tagged for a different VLAN, to route between VLANs over a trunk. Each subinterface acts as the default gateway for its VLAN. This design trades scalability for lower cost than one physical link per VLAN.

Question 50Routing and Switching

Which OSPF router type connects one area to the backbone area and injects summarized routes into that area?

  1. Area Border Router Correct answer.
  2. Autonomous System Boundary Router
  3. Designated Router
  4. Internal router

Explanation

An Area Border Router has interfaces in two or more areas, one of which must be area 0. It maintains a separate link-state database per area and can summarize prefixes between areas. This keeps topology details local to each area.