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JNCIA-DC practice questions

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Question 1Data Center Architecture and Networking Fundamentals

In a Juniper data center design, which component is responsible for maintaining the forwarding table that is used to make per-packet forwarding decisions?

  1. The Routing Engine
  2. The Packet Forwarding Engine Correct answer.
  3. The management Ethernet interface
  4. The master control board's flash storage

Explanation

Junos separates control-plane and data-plane functions. The Routing Engine runs routing protocols and builds the routing table, then programs the resulting forwarding table into the Packet Forwarding Engine, which performs the actual per-packet lookups and forwarding.

Question 2Data Center Architecture and Networking Fundamentals

Which Juniper data center switch family is purpose-built as a fixed-form-factor spine or leaf platform running Junos and supporting high-density 100GbE ports?

  1. EX Series
  2. SRX Series
  3. QFX Series Correct answer.
  4. MX Series

Explanation

The QFX Series is Juniper's data center switching portfolio, designed for IP fabric leaf-and-spine roles with high-density 40GbE/100GbE/400GbE interfaces. SRX is a security services gateway, EX targets campus/enterprise access, and MX is a service provider edge router.

Question 3Data Center Architecture and Networking Fundamentals

In a typical IP fabric, what is the primary role of the spine layer?

  1. To provide a high-bandwidth, low-latency interconnect between all leaf switches Correct answer.
  2. To perform stateful firewall inspection between tenants
  3. To terminate server VLANs and apply Layer 2 access policies
  4. To act as the default gateway for all attached servers

Explanation

Spines form the backbone of an IP fabric, connecting to every leaf with equal-cost links so traffic between leaves traverses a predictable number of hops. Server attachment, default gateway functions, and tenant policy are handled at the leaf layer.

Question 4Data Center Architecture and Networking Fundamentals

Which statement describes a characteristic advantage of a Layer 3 IP fabric over a traditional Layer 2 data center design?

  1. It requires Spanning Tree Protocol on every uplink
  2. It eliminates the need for any routing protocol
  3. It restricts traffic to a single active path to avoid loops
  4. It uses equal-cost multipath to utilize all available links Correct answer.

Explanation

An IP fabric routes between leaf and spine over many equal-cost links, so ECMP load-shares traffic across all of them. Layer 2 designs block redundant links with STP, leaving capacity unused and creating larger failure domains.

Question 5Data Center Architecture and Networking Fundamentals

A design uses every leaf switch to peer with every spine switch over eBGP. Which term describes this peering model?

  1. Ring topology
  2. Full mesh Correct answer.
  3. Route reflection
  4. Hub and spoke

Explanation

When each leaf establishes a session with each spine, the resulting adjacency pattern is a full mesh between the two tiers. Route reflection is a technique to avoid needing a full iBGP mesh, and hub-and-spoke or ring patterns do not describe leaf-to-spine peering.

Question 6Data Center Architecture and Networking Fundamentals

Why is BGP commonly selected as the underlay routing protocol in large Juniper IP fabrics?

  1. It is the only protocol that supports IPv6 addressing
  2. It provides scalable policy control and stable multipath forwarding across many nodes Correct answer.
  3. It automatically encrypts all traffic between leaf and spine
  4. It removes the need to assign unique AS numbers or addresses

Explanation

BGP scales well, offers rich policy tools, and supports multipath so ECMP can use all fabric links. It is not an encryption protocol, does not remove addressing requirements, and is not the sole IPv6-capable protocol.

Question 7Data Center Architecture and Networking Fundamentals

In an EVPN-VXLAN architecture, what is the function of the VXLAN Network Identifier (VNI)?

  1. It encodes the MTU for the tunnel
  2. It specifies the BGP autonomous system of the leaf
  3. It identifies a Layer 2 or Layer 3 overlay segment across the fabric Correct answer.
  4. It identifies the physical spine port used for a flow

Explanation

The VNI is a 24-bit identifier carried in the VXLAN header that scopes an overlay segment, allowing the same VLAN to be stretched or kept separate across the fabric. It is not tied to physical ports, BGP AS numbers, or MTU values.

Question 8Data Center Architecture and Networking Fundamentals

Which protocol does EVPN use to distribute MAC and IP reachability information across the data center fabric?

  1. LACP with vendor TLVs
  2. BGP with EVPN address family Correct answer.
  3. STP with BPDU extensions
  4. OSPFv2 with opaque LSAs

Explanation

EVPN is defined as a BGP address family (AFI 25, SAFI 70) that carries MAC and IP reachability in route types. OSPF, STP, and LACP do not provide EVPN route distribution.

Question 9Data Center Architecture and Networking Fundamentals

What does a Type 2 EVPN route advertise?

  1. A MAC address with an optional IP address Correct answer.
  2. An IP prefix for the underlay
  3. An inclusive multicast endpoint set
  4. An Ethernet segment identifier for multihoming

Explanation

Type 2 routes are MAC/IP advertisement routes, used for host MAC learning and for ARP/ND suppression and symmetric IRB. Type 1 carries Ethernet segment information, Type 3 carries inclusive multicast, and Type 5 carries IP prefixes.

Question 10Data Center Architecture and Networking Fundamentals

Which EVPN route type is used to advertise an IP prefix, enabling Layer 3 overlay routing without a corresponding MAC advertisement?

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

Explanation

Type 5 (IP prefix) routes advertise IP prefixes across the EVPN fabric, supporting Layer 3 routing for subnets that are not tied to a specific host MAC. Type 2 can carry IP but is host-oriented, while Types 1 and 3 handle segment discovery and multicast.

Question 11Data Center Architecture and Networking Fundamentals

In a VXLAN data plane, which device performs the encapsulation and decapsulation of tenant frames?

  1. The DHCP relay
  2. The NTP server
  3. The VTEP Correct answer.
  4. The route reflector

Explanation

A VXLAN Tunnel Endpoint (VTEP) originates and terminates VXLAN tunnels, adding or removing the outer header. Route reflectors distribute BGP routes, and DHCP relay and NTP servers provide unrelated services.

Question 12Data Center Architecture and Networking Fundamentals

What is the purpose of the underlay network in an EVPN-VXLAN fabric?

  1. To provide IP reachability between VTEP loopback addresses Correct answer.
  2. To terminate server VLAN interfaces
  3. To distribute EVPN route types to all leaves
  4. To carry tenant MAC addresses between leaf switches

Explanation

The underlay provides routed IP connectivity, typically via eBGP or OSPF, so that VTEP loopback addresses can reach each other and VXLAN packets can be tunneled. Tenant MAC learning and EVPN route distribution happen in the overlay.

Question 13Data Center Architecture and Networking Fundamentals

On a Juniper switch, what does an IRB interface provide in a data center design?

  1. A routed Layer 3 interface associated with a VLAN, used as a gateway Correct answer.
  2. A Layer 2 trunk carrying all VLANs by default
  3. A loopback used only for BGP router ID selection
  4. A dedicated out-of-band management path

Explanation

An Integrated Routing and Bridging (IRB) interface gives a VLAN a Layer 3 presence, allowing the switch to act as the default gateway for hosts in that VLAN. Management paths, trunk behavior, and router IDs are handled by other constructs.

Question 14Data Center Architecture and Networking Fundamentals

Which Junos feature allows a single physical interface to carry multiple logical units, each associated with a different VLAN?

  1. Aggregated Ethernet
  2. VLAN tagging on logical units Correct answer.
  3. Virtual Chassis
  4. Class of service

Explanation

Junos supports 802.1Q VLAN tagging, where each logical unit on a physical interface is bound to a VLAN ID. Aggregated Ethernet bundles links, Virtual Chassis combines switches, and CoS handles traffic treatment.

Question 15Data Center Architecture and Networking Fundamentals

A design requires link aggregation between a server and two leaf switches so that the server remains reachable if one leaf fails. Which approach fits an EVPN-VXLAN fabric?

  1. A routed port-channel with OSPF on the server
  2. Two independent LAGs with different IP addresses
  3. A multihomed Ethernet segment using EVPN multihoming (ESI-LAG) Correct answer.
  4. A single LAG to one leaf with STP blocking the second link

Explanation

EVPN multihoming lets a server form a LAG across multiple leaves by assigning a shared Ethernet Segment Identifier, providing redundancy without STP. Single-homing with blocked links, split LAGs, or running OSPF on a server do not deliver the intended active-active multihoming.

Question 16Data Center Architecture and Networking Fundamentals

What is the role of a route reflector in a large iBGP-based data center fabric?

  1. It reflects routes between iBGP peers so a full mesh of sessions is not required Correct answer.
  2. It performs VXLAN encapsulation for attached servers
  3. It assigns VNIs to tenant VLANs
  4. It forwards data traffic between leaves

Explanation

A route reflector re-advertises routes learned from one iBGP client to other clients, removing the need for every router to peer with every other router. It does not forward tenant data, assign VNIs, or encapsulate traffic.

Question 17Data Center Architecture and Networking Fundamentals

Which statement accurately describes a Virtual Chassis or Virtual Chassis Fabric deployment in a data center?

  1. It eliminates the need for any inter-switch cabling
  2. Each switch keeps an independent control plane but shares a single forwarding table
  3. It requires all member switches to run different Junos versions
  4. Multiple switches are managed as a single logical device with a shared control plane Correct answer.

Explanation

Virtual Chassis combines member switches into one logical device with a single management and control plane, simplifying operations. Members still have separate forwarding hardware, must run compatible Junos releases, and require inter-switch links.

Question 18Data Center Architecture and Networking Fundamentals

What is the primary purpose of a link aggregation group (LAG) between a leaf switch and a server?

  1. To increase bandwidth and provide link redundancy Correct answer.
  2. To replace the need for a default gateway
  3. To assign a unique IP subnet per physical link
  4. To encrypt traffic between the server and switch

Explanation

A LAG bundles multiple physical links into one logical link, increasing aggregate bandwidth and allowing traffic to continue if a member link fails. It does not create per-link subnets, encrypt traffic, or remove the need for a gateway.

Question 19Data Center Architecture and Networking Fundamentals

In a Juniper IP fabric, what is the recommended purpose of a loopback interface on each leaf and spine?

  1. To provide a stable router ID and a stable address for routing sessions and VTEPs Correct answer.
  2. To carry tenant VLAN traffic
  3. To terminate server LAGs
  4. To connect to the out-of-band management network

Explanation

Loopback interfaces are always up and independent of physical link state, so they provide stable router IDs and stable endpoints for BGP sessions and VTEP addresses. They are not used for tenant VLAN transport, management access, or server attachment.

Question 20Data Center Architecture and Networking Fundamentals

Which mechanism allows an IP fabric to distribute traffic across multiple equal-cost paths between a leaf and a spine?

  1. Equal-cost multipath (ECMP) Correct answer.
  2. Proxy ARP
  3. Spanning Tree Protocol
  4. VLAN pruning

Explanation

ECMP installs multiple next hops of equal cost into the forwarding table so traffic is hashed across all available paths. STP blocks redundant links, VLAN pruning limits flooding, and proxy ARP affects address resolution rather than path selection.

Question 21Data Center Architecture and Networking Fundamentals

A design team wants to reduce the size of the Layer 2 failure domain in a data center. Which approach best achieves this?

  1. Use a single large VLAN for all servers
  2. Disable all routing protocols and rely on STP
  3. Route between subnets at the leaf and limit Layer 2 to the access segment Correct answer.
  4. Extend VLANs across the entire fabric to every leaf

Explanation

Keeping Layer 2 local to the leaf and routing between subnets confines broadcast and failure domains. Extending VLANs fabric-wide or using one large VLAN enlarges the Layer 2 domain, and disabling routing increases reliance on STP.

Question 22Data Center Architecture and Networking Fundamentals

What does the term 'overlay' refer to in an EVPN-VXLAN data center design?

  1. The physical cabling between switches
  2. The management network used for device access
  3. The power and cooling infrastructure
  4. The logical network built over the underlay using tunnels and EVPN control plane Correct answer.

Explanation

The overlay is a logical network constructed on top of the routed underlay, using VXLAN tunnels and EVPN signaling to deliver tenant segments. Physical cabling, management access, and facility infrastructure are not overlays.

Question 23Data Center Architecture and Networking Fundamentals

Which Junos command displays the routes installed in the forwarding table for a given destination?

  1. show route forwarding-table destination <prefix> Correct answer.
  2. show chassis hardware
  3. show system uptime
  4. show configuration interfaces

Explanation

The forwarding table reflects what the Packet Forwarding Engine will actually use, and 'show route forwarding-table destination' filters it by prefix. The other commands display configuration, hardware inventory, or uptime and do not show forwarding entries.

Question 24Data Center Architecture and Networking Fundamentals

In an EVPN-VXLAN fabric using symmetric IRB, how is inter-subnet traffic between two leaves handled?

  1. It is sent to a dedicated external firewall for all inter-subnet flows
  2. It is always dropped unless both hosts are on the same leaf
  3. It is bridged at Layer 2 across the fabric with no routing
  4. It is routed at the ingress leaf, tunneled to the egress leaf, and routed again there Correct answer.

Explanation

Symmetric IRB routes the packet at the ingress VTEP into a VXLAN tunnel that carries both source and destination VNIs, and the egress VTEP performs the final Layer 3 lookup. This avoids bridging between subnets and does not require a central firewall for basic inter-subnet traffic.

Question 25Data Center Architecture and Networking Fundamentals

Which benefit does EVPN provide over traditional flood-and-learn VXLAN for MAC address learning?

  1. It distributes MAC reachability via BGP control plane instead of relying on data-plane flooding Correct answer.
  2. It removes the need for VTEPs
  3. It guarantees that no broadcast traffic ever occurs
  4. It eliminates the need for any routing protocol

Explanation

EVPN advertises MAC (and IP) reachability through BGP, so VTEPs learn remote hosts from the control plane rather than from flooded data-plane traffic. Routing protocols are still needed, VTEPs remain essential, and broadcast handling still exists for BUM traffic.

Question 26Data Center Architecture and Networking Fundamentals

In a spine-leaf IP fabric, what is the primary reason every leaf connects to every spine?

  1. To provide a single management path for all devices
  2. To eliminate the need for routing protocols
  3. To allow servers to share a single broadcast domain across all racks
  4. To guarantee that any leaf can reach any other leaf through a single spine hop, keeping the fabric two tiers Correct answer.

Explanation

A full mesh between leaves and spines keeps the fabric at two tiers, so server-to-server traffic crosses exactly one spine device. This bounded diameter gives predictable, low, and uniform latency regardless of which leaves are involved. It also makes equal-cost multipathing symmetric across the fabric.

Question 27Data Center Architecture and Networking Fundamentals

Which statement describes the role of a border leaf (also called a border or edge device) in a data center IP fabric?

  1. It replaces the spine layer for external traffic
  2. It acts as the route reflector for the entire fabric
  3. It provides connectivity between the fabric and external networks such as WAN, Internet, or legacy data center domains Correct answer.
  4. It terminates all VXLAN tunnels from every server rack

Explanation

Border leaves connect the fabric to the outside world, hosting handoffs to WAN edge routers, firewalls, or legacy networks. Keeping this function on dedicated leaves avoids adding external state and policy to every leaf. Spine devices remain pure high-speed transit.

Question 28Data Center Architecture and Networking Fundamentals

What is the main purpose of a Layer 3 IP fabric underlay compared with a traditional Layer 2 core?

  1. It removes the need for any overlay technology
  2. It provides a loop-free, multipath-routed transport that scales without large broadcast domains Correct answer.
  3. It uses STP to prevent loops between switches
  4. It allows VLANs to span the entire data center

Explanation

An IP underlay routes packets using a dynamic routing protocol, so loops are prevented by routing rather than by blocking links with STP. All links can forward simultaneously through ECMP, and broadcast domains stay small. This scales far better than a large bridged core.

Question 29Data Center Architecture and Networking Fundamentals

Which device type typically hosts the VXLAN Tunnel Endpoint (VTEP) function in an EVPN-VXLAN fabric?

  1. The core routers
  2. The spine switches
  3. The out-of-band management switches
  4. The leaf switches Correct answer.

Explanation

VTEPs are placed on the leaf switches, which are closest to the servers and can encapsulate tenant frames into VXLAN. Spines only route the encapsulated packets and do not need to know tenant VNIs. This keeps tenant state at the fabric edge.

Question 30Data Center Architecture and Networking Fundamentals

In Junos, which interface type is used to give a VLAN an IP address so the switch can route traffic for that VLAN?

  1. A physical interface with an address directly
  2. An integrated routing and bridging (IRB) interface Correct answer.
  3. A tunnel interface
  4. A loopback interface

Explanation

An IRB interface, named irb.<unit> in Junos, is a Layer 3 interface bound to a VLAN, allowing the device to route for hosts in that VLAN. It provides the default gateway for the subnet. Physical interfaces normally remain Layer 2 members of the VLAN.

Question 31Data Center Architecture and Networking Fundamentals

What does the term 'symmetric IRB' mean in an EVPN-VXLAN design?

  1. Traffic is routed only at the egress leaf
  2. Traffic is routed only at the ingress leaf
  3. Traffic is routed at both the ingress leaf and the egress leaf Correct answer.
  4. Traffic is bridged across all leaves

Explanation

Symmetric IRB routes packets into the VXLAN tunnel at the ingress leaf and routes them again out of the tunnel at the egress leaf. Each leaf therefore holds an IRB for every tenant VLAN, and VNIs are mapped consistently across the fabric. This avoids per-VLAN VNI mapping complexity found in asymmetric designs.

Question 32Data Center Architecture and Networking Fundamentals

A network engineer wants to verify the underlay routing adjacencies on a leaf switch. Which Junos command shows BGP neighbor state?

  1. show chassis hardware
  2. show ethernet-switching table
  3. show vlans
  4. show bgp summary Correct answer.

Explanation

The show bgp summary command lists each configured neighbor, its state, and prefix counts received, which is the standard way to confirm underlay BGP sessions are Established. Underlay health is a prerequisite before overlay EVPN sessions can work.

Question 33Data Center Architecture and Networking Fundamentals

Which statement best explains why a dedicated loopback address is used as the BGP router ID and peering address in an IP fabric?

  1. It provides a stable address that stays reachable as long as any path through the fabric exists Correct answer.
  2. It allows the device to bypass routing and forward at Layer 2
  3. It is required for VXLAN encapsulation
  4. It is the only interface that supports IPv6

Explanation

A loopback is always up and reachable through the routed fabric regardless of which physical link fails, so BGP sessions survive link changes. Peering to loopbacks requires an IGP or static routes to make them reachable. This stability is why loopbacks are used for peering and VTEP source addresses.

Question 34Data Center Architecture and Networking Fundamentals

What is a key advantage of using a Layer 3 IP fabric with ECMP for server-to-server traffic compared with a Layer 2 spanning-tree design?

  1. It reduces the number of IP addresses required
  2. It requires fewer physical switches
  3. It eliminates the need for any routing protocol
  4. It uses all available parallel links for forwarding rather than blocking redundant links Correct answer.

Explanation

With ECMP, all equal-cost paths are installed in the forwarding table and traffic is hashed across them, so every uplink carries traffic. Spanning tree instead blocks redundant links to prevent loops, leaving capacity unused. This is a primary reason IP fabrics are chosen for scale-out data centers.

Question 35Data Center Architecture and Networking Fundamentals

In Junos EVPN-VXLAN, which statement describes the function of a VNI-to-VLAN mapping on a leaf?

  1. It configures the physical port speed
  2. It defines the BGP autonomous system number
  3. It associates a VLAN with a VXLAN segment so local bridging and tunnel encapsulation use the same identifier Correct answer.
  4. It assigns the VNI as the IP address of the IRB

Explanation

The VNI-to-VLAN map ties a local VLAN to a VXLAN network identifier so frames from that VLAN are encapsulated with the correct VNI. Consistent mapping across leaves allows hosts in the same segment to communicate over the overlay. The VNI is a data-plane identifier, not an IP address.

Question 36Data Center Architecture and Networking Fundamentals

What does an EVPN Type 5 route advertise in a data center fabric?

  1. A MAC address and its associated IP address
  2. A VTEP tunnel endpoint address only
  3. An IP prefix for Layer 3 routing Correct answer.
  4. A multicast group membership

Explanation

Type 5 routes carry IP prefix information, enabling Layer 3 overlay routing for subnets that may not have locally attached hosts. They are used for inter-subnet and external prefix reachability in EVPN. Type 2 routes, in contrast, carry MAC and IP host information.

Question 37Data Center Architecture and Networking Fundamentals

Which EVPN route type is used for inclusive multicast Ethernet tag routes that help establish BUM traffic delivery?

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

Explanation

Type 3 routes advertise VTEP membership in an EVPN instance, allowing ingress VTEPs to build the flooding list for broadcast, unknown unicast, and multicast traffic. They replace flood-and-learn behavior for BUM traffic distribution. Type 2 routes, by contrast, advertise host MAC and IP bindings.

Question 38Data Center Architecture and Networking Fundamentals

A design uses EVPN multihoming with an Ethernet segment identifier (ESI) on two leaf switches connected to the same server. What is the purpose of the designated forwarder election?

  1. To choose the VNI for the segment
  2. To select one leaf to forward BUM traffic for the segment and avoid duplicates Correct answer.
  3. To elect the BGP route reflector
  4. To assign the server's IP address

Explanation

When a multihomed segment has multiple leaves attached, BUM traffic must be delivered by only one of them to prevent duplicate frames reaching the server. Designated forwarder election picks that leaf per segment. All-active forwarding of known unicast can still use both leaves.

Question 39Data Center Architecture and Networking Fundamentals

What is the purpose of a Virtual Chassis in a Juniper data center design?

  1. To encrypt traffic between leaf and spine
  2. To combine multiple switches into a single logical device with one management address and control plane Correct answer.
  3. To provide Layer 3 routing between data centers
  4. To replace BGP with OSPF

Explanation

Virtual Chassis links multiple physical switches into one logical chassis that is managed and configured as a single device. This simplifies management and can provide redundant control planes. It is distinct from an IP fabric, where each device is managed separately.

Question 40Data Center Architecture and Networking Fundamentals

Which Junos feature allows a single physical interface to carry multiple VLANs, each with its own logical unit?

  1. Integrated routing and bridging
  2. Aggregated Ethernet
  3. Trunk mode with tagged logical interfaces Correct answer.
  4. Loopback filtering

Explanation

Configuring an interface in trunk mode with multiple tagged logical units lets one physical link carry several VLANs, each identified by an 802.1Q tag. This is the standard way to connect a server or switch that needs multiple segments over one cable. Each unit is bound to a VLAN.

Question 41Data Center Architecture and Networking Fundamentals

In a Juniper IP fabric, which protocol is commonly used as the underlay routing protocol to advertise loopbacks and point-to-point link addresses?

  1. STP
  2. VXLAN
  3. BGP Correct answer.
  4. LLDP

Explanation

BGP is widely used in the underlay because it scales well, supports policy, and is the same protocol used for the EVPN overlay. It advertises loopback addresses and link prefixes so VTEPs and peers are reachable. STP and LLDP are not routing protocols, and VXLAN is an encapsulation.

Question 42Data Center Architecture and Networking Fundamentals

What does a Type 2 EVPN route advertise when it includes both MAC and IP information?

  1. A MAC address and its associated IP address for a host Correct answer.
  2. A VTEP's inclusive multicast membership
  3. An IP prefix with no host binding
  4. An Ethernet segment identifier for multihoming

Explanation

Type 2 routes carry MAC and IP bindings for hosts learned in an EVPN instance, enabling both Layer 2 and Layer 3 forwarding decisions. Including the IP allows ARP suppression and efficient routing. This is the core host reachability route in EVPN.

Question 43Data Center Architecture and Networking Fundamentals

An engineer observes that a leaf switch has two equal-cost paths to a remote loopback but only one path is being used. Which factor most likely explains this?

  1. The loopback interface is down
  2. The routing protocol has not installed both paths in the forwarding table Correct answer.
  3. VXLAN encapsulation is disabled
  4. The server is using the wrong default gateway

Explanation

ECMP requires the routing protocol to install multiple equal-cost next hops into the forwarding table. If only one path is present, the protocol may not have received or selected the second path, or a policy may be filtering it. Checking the route detail and forwarding table confirms next-hop selection.

Question 44Data Center Architecture and Networking Fundamentals

Which statement describes the benefit of ARP suppression in an EVPN-VXLAN fabric?

  1. It replaces BGP with a static ARP table
  2. It encrypts ARP packets between leaves
  3. It reduces ARP flooding by answering requests from EVPN-learned MAC and IP bindings Correct answer.
  4. It eliminates the need for IP routing entirely

Explanation

When a leaf has learned a host's MAC and IP through EVPN Type 2 routes, it can answer ARP requests locally instead of flooding them across the overlay. This reduces BUM traffic and ARP load on hosts. It complements, rather than replaces, routing and control-plane protocols.

Question 45Data Center Architecture and Networking Fundamentals

What is the function of a route reflector in an iBGP-based data center fabric?

  1. It reflects routes between iBGP peers so a full mesh of sessions is not required Correct answer.
  2. It provides Layer 2 loop prevention
  3. It redistributes routes between OSPF areas
  4. It assigns VTEP addresses automatically

Explanation

A route reflector receives routes from iBGP peers and reflects them to other clients, removing the need for every router to peer with every other router. This is essential for scaling iBGP in a large fabric. It operates purely in the control plane.

Question 46Data Center Architecture and Networking Fundamentals

Which Junos command displays the EVPN routes received from BGP peers on a leaf switch?

  1. show interfaces terse
  2. show ethernet-switching table
  3. show evpn database
  4. show route table bgp.evpn.0 Correct answer.

Explanation

EVPN routes are stored in the bgp.evpn.0 routing table, so show route table bgp.evpn.0 displays received route types and their attributes. This is useful for verifying that Type 2 and Type 5 routes have been learned. The EVPN database shows locally and remotely learned MAC information.

Question 47Data Center Architecture and Networking Fundamentals

In an EVPN-VXLAN design, what is the primary role of the underlay network?

  1. To perform MAC learning for tenant hosts
  2. To provide Layer 2 flooding across all racks
  3. To provide IP reachability between VTEPs so encapsulated packets can be delivered Correct answer.
  4. To carry tenant VLAN tags between servers

Explanation

The underlay provides routed IP connectivity between VTEP loopback addresses, allowing VXLAN-encapsulated packets to traverse the fabric. It does not need to know about tenant VNIs. Tenant MAC learning and VLAN semantics are handled by the overlay.

Question 48Data Center Architecture and Networking Fundamentals

Which statement accurately describes a Virtual Chassis Fabric (VCF) deployment compared with a standard IP fabric?

  1. VCF eliminates the need for any routing
  2. VCF presents a spine-and-leaf topology as a single logical device managed with one configuration Correct answer.
  3. VCF is used only for connecting to the Internet
  4. VCF requires BGP between every leaf and spine

Explanation

VCF combines spine and leaf devices into one logical, centrally managed fabric, simplifying configuration and operations. It is an alternative deployment model to a routed IP fabric where each device is managed independently. It still forwards traffic across a spine-and-leaf topology.

Question 49Data Center Architecture and Networking Fundamentals

In a Juniper data center fabric, which statement best describes the purpose of a Layer 3 IP underlay built from point-to-point links between leaf and spine devices?

  1. It provides loop-free, equal-cost multipath forwarding between leaves so any leaf reaches any other leaf over the spine tier. Correct answer.
  2. It aggregates access ports into link aggregation bundles toward dual-homed servers.
  3. It delivers VXLAN encapsulation between leaf devices so overlay frames can traverse the spine tier.
  4. It extends a single broadcast domain across all racks so servers in different pods share one subnet.

Explanation

The underlay is a routed fabric: each leaf and spine forms a point-to-point IP link, and a routing protocol advertises loopback addresses so traffic is forwarded hop by hop with ECMP across all available spines. Because every link is a separate subnet and routing is hop by hop, no Spanning Tree blocking exists and all paths can be used. VXLAN encapsulation and broadcast-domain extension belong to the overlay, while server bundling is an access-layer function.

Question 50Data Center Architecture and Networking Fundamentals

A design places two leaf switches in the same rack, each with an anycast gateway address configured for VLAN 100. A server on leaf A sends traffic to a host on leaf B in the same VLAN 100 subnet. How does the fabric forward this traffic?

  1. Leaf A routes the packet using the anycast gateway MAC, encapsulates it in VXLAN, and sends it over the IP underlay to leaf B. Correct answer.
  2. Leaf A forwards the frame to the spine, which performs the inter-VLAN routing and returns it to leaf B.
  3. The frame is bridged across a stretched Layer 2 segment through the spines without any routing lookup.
  4. Leaf A floods the frame to all VTEPs because the destination MAC is unknown, and leaf B replies with a proxy ARP response.

Explanation

With symmetric or asymmetric IRB using an anycast gateway, each leaf acts as the default gateway for the VLAN using the same virtual MAC address. Traffic between hosts in the same subnet but on different leaves is routed at the ingress leaf, encapsulated with the destination VNI, and forwarded over the underlay to the remote VTEP. This avoids stretching a Layer 2 segment across the spine tier and keeps bridging local to each leaf.