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Arista ACE Specialist - Data Center study materials
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Arista ACE Specialist - Data Center practice questions

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Question 1Data Center Networking Fundamentals

In a leaf-spine data center fabric, what is the primary purpose of a spine layer?

  1. To provide high-bandwidth, low-latency interconnect between all leaf switches Correct answer.
  2. To serve as the management plane for fabric-wide orchestration
  3. To terminate storage traffic and provide FCoE gateway services
  4. To aggregate access-layer VLANs and apply host-facing security policies

Explanation

In a leaf-spine design every leaf connects to every spine, and spines act purely as a high-capacity transit layer that never connects to hosts. This gives predictable any-to-any latency and even ECMP distribution.

Question 2Data Center Networking Fundamentals

Which statement best describes a Layer 2 leaf-spine fabric using VXLAN?

  1. It restricts each VLAN to a single leaf switch
  2. It requires STP to prevent loops across every spine uplink
  3. It tunnels Layer 2 frames over an IP underlay between VTEPs Correct answer.
  4. It eliminates the need for any routing protocol in the underlay

Explanation

VXLAN encapsulates original Ethernet frames in UDP/IP so Layer 2 segments can stretch across a routed Layer 3 underlay. The underlay routes between VTEP loopback addresses while the overlay provides the Layer 2 service.

Question 3Data Center Networking Fundamentals

What does ECMP allow a leaf switch to do when it has four equal-cost paths to a destination?

  1. Disable three of the paths until the primary fails
  2. Route only Layer 2 traffic across the paths
  3. Serialize traffic onto a single path to preserve ordering
  4. Load-balance flows across all four paths simultaneously Correct answer.

Explanation

Equal-Cost Multi-Path installs multiple next hops for the same prefix and hashes flows across them, which is what makes leaf-spine fabrics scale. Hashing is per-flow, so individual flow ordering is preserved.

Question 4Data Center Networking Fundamentals

Which protocol is most commonly used to build the routed underlay of a modern data center fabric?

  1. RIP version 2
  2. BGP Correct answer.
  3. OSPFv1
  4. IS-IS for IPv6 only

Explanation

eBGP is widely used for the fabric underlay because it scales well, supports multipath, and gives clean policy control between leaf and spine. OSPF is also valid, but BGP is the dominant choice.

Question 5Data Center Networking Fundamentals

What is the role of a VTEP in a VXLAN fabric?

  1. It provides Power over Ethernet to access points
  2. It assigns IP addresses to hosts via DHCP relay
  3. It monitors fabric health and reports to a controller
  4. It encapsulates and decapsulates tenant frames into VXLAN tunnels Correct answer.

Explanation

A VXLAN Tunnel Endpoint originates and terminates VXLAN tunnels by adding or removing the VXLAN header and outer IP/UDP headers. It is typically a loopback interface on a leaf switch.

Question 6Data Center Networking Fundamentals

What does a /24 prefix in a fabric underlay represent?

  1. 24 usable host addresses
  2. A subnet mask of 255.255.255.0 Correct answer.
  3. 24 equal-cost paths
  4. A VLAN ID range of 24

Explanation

The /24 notation is CIDR prefix length, equivalent to a 255.255.255.0 subnet mask. It leaves 8 host bits, giving 254 usable addresses after network and broadcast.

Question 7Data Center Networking Fundamentals

Which benefit does a spine-leaf topology provide over a traditional three-tier campus design for east-west traffic?

  1. It eliminates the need for redundant power
  2. Traffic crosses fewer hops with more consistent latency Correct answer.
  3. It removes the need for Layer 3 routing
  4. Fewer physical links are required overall

Explanation

Because every leaf connects to every spine, any server-to-server path is a fixed two-hop leaf-spine-leaf path. This gives predictable, uniform latency for east-west traffic compared with multi-tier designs.

Question 8Data Center Networking Fundamentals

What is the purpose of a VNI in a VXLAN network?

  1. It assigns a unique IP to each leaf switch
  2. It sets the MTU for the underlay
  3. It identifies a tenant Layer 2 segment in the overlay Correct answer.
  4. It defines the BGP autonomous system number

Explanation

The VXLAN Network Identifier is a 24-bit value that identifies an isolated Layer 2 segment in the overlay, allowing millions of segments. It is carried in the VXLAN header of each encapsulated frame.

Question 9Data Center Networking Fundamentals

A fabric has 4 spines and 16 leaves, with every leaf connected to every spine. How many uplink links exist in total?

  1. 256
  2. 20
  3. 64 Correct answer.
  4. 16

Explanation

Each of the 16 leaves connects to all 4 spines, so 16 × 4 = 64 uplinks. Each spine in turn has 16 downlinks, which is the same total counted from the spine side.

Question 10Data Center Networking Fundamentals

Why is jumbo MTU typically configured on fabric underlay interfaces carrying VXLAN traffic?

  1. To accommodate the extra encapsulation headers without fragmenting tenant frames Correct answer.
  2. To reduce the size of routing tables
  3. To speed up BGP convergence
  4. To allow more VLANs per interface

Explanation

VXLAN adds outer IP, UDP, and VXLAN headers, so the tunneled frame exceeds the original tenant frame size. Raising the underlay MTU prevents fragmentation and dropped oversized packets.

Question 11Data Center Networking Fundamentals

What is the primary function of an anycast gateway in a VXLAN fabric?

  1. To encrypt tenant traffic between leaves
  2. To load-balance traffic across multiple WAN links
  3. To elect one leaf as the sole gateway for the whole fabric
  4. To provide a single shared default gateway MAC and IP on every leaf Correct answer.

Explanation

Anycast gateway configures the same distributed gateway IP and MAC on every leaf, so a host's first-hop gateway is always local. This enables optimal routing without tromboning traffic across the fabric.

Question 12Data Center Networking Fundamentals

A server on leaf A in VLAN 100 needs to reach a server on leaf B in VLAN 200. In a VXLAN fabric with distributed anycast gateways, how is the traffic handled?

  1. It is dropped because VLANs cannot cross leaves
  2. It must pass through a dedicated central gateway spine
  3. It is bridged directly at Layer 2 because VXLAN ignores VLAN boundaries
  4. It is routed at leaf A and encapsulated to leaf B's VTEP for the destination subnet Correct answer.

Explanation

The source leaf performs the inter-subnet routing locally using its anycast gateway and then VXLAN-encapsulates the packet toward the destination VTEP. This keeps the first hop local and avoids centralized gateway bottlenecks.

Question 13Data Center Networking Fundamentals

Which statement about VXLAN versus traditional VLANs is accurate?

  1. VXLAN requires STP to block redundant paths
  2. VXLAN uses 802.1Q tags in place of an IP header
  3. VXLAN supports far more segments than the 4094 VLAN limit Correct answer.
  4. VXLAN segments cannot span more than one switch

Explanation

VXLAN uses a 24-bit VNI, allowing roughly 16 million segments versus the 12-bit VLAN ID limit of about 4094. This scalability is a key driver for VXLAN adoption.

Question 14Data Center Networking Fundamentals

What does a leaf switch do when it receives a frame for an unknown unicast destination in a VXLAN fabric with EVPN control plane?

  1. It forwards to remote VTEPs learned via EVPN MAC/IP routes, using head-end replication only for unknown MACs Correct answer.
  2. It waits for STP to converge before forwarding
  3. It drops the frame and sends an ICMP unreachable
  4. It floods the frame to every port in the VLAN

Explanation

EVPN distributes MAC and IP reachability, so most destinations are known and forwarded unicast. For genuinely unknown MACs, ingress replication (head-end replication) sends copies to the relevant remote VTEPs.

Question 15Data Center Networking Fundamentals

Which field in the VXLAN header identifies the tenant segment?

  1. The inner 802.1Q tag
  2. The outer source IP address
  3. The 24-bit VNI Correct answer.
  4. The outer destination UDP port

Explanation

The VNI field in the VXLAN header is the 24-bit identifier that maps a frame to its tenant Layer 2 segment. The outer UDP destination port is typically 4789 and does not identify the tenant.

Question 16Data Center Networking Fundamentals

What is the main purpose of BGP EVPN in a data center fabric?

  1. To provide encryption of tenant traffic
  2. To distribute MAC and IP reachability for the VXLAN overlay Correct answer.
  3. To replace OSPF in the underlay
  4. To manage power and cooling of switches

Explanation

EVPN uses BGP to advertise MAC and IP reachability (Type 2 routes) and other overlay information, enabling control-plane learning instead of data-plane flooding. The underlay remains a separate routing domain.

Question 17Data Center Networking Fundamentals

A network engineer observes that traffic between two leaves takes a longer path through a spine even though both leaves share a direct link. What design principle explains this?

  1. Direct leaf links are used only for management
  2. ECMP requires at least three hops
  3. Spines must always be traversed for security
  4. Leaf-spine fabrics intentionally avoid leaf-to-leaf links Correct answer.

Explanation

In a strict leaf-spine topology, leaves never connect to each other; all inter-leaf traffic transits a spine. This keeps the fabric uniform and avoids complex leaf-to-leaf peering.

Question 18Data Center Networking Fundamentals

Which hash input is commonly used by ECMP to keep a single TCP flow on one path?

  1. The VLAN priority bits
  2. The 5-tuple of source/destination IP and ports plus protocol Correct answer.
  3. The TTL field
  4. Source MAC address only

Explanation

ECMP hashes on the flow's 5-tuple so all packets of a flow take the same path, preserving ordering. Using only the source MAC would not distinguish flows between the same pair of hosts.

Question 19Data Center Networking Fundamentals

What is the effect of configuring a larger prefix length on a route in the fabric underlay?

  1. It increases the administrative distance
  2. It makes the route more specific and preferred over shorter prefixes Correct answer.
  3. It disables ECMP for that route
  4. It forces the route into a VLAN

Explanation

Longest-prefix match is the primary tiebreaker in IP forwarding, so a /32 loopback route is preferred over a /24 covering the same address range. Administrative distance is only consulted among routes of equal prefix length.

Question 20Data Center Networking Fundamentals

In an EVPN fabric, a Type 2 route advertises which information?

  1. An Ethernet segment's designated forwarder
  2. A MAC address and its associated IP and VTEP Correct answer.
  3. A multicast group membership
  4. An IP prefix for the underlay

Explanation

EVPN Type 2 (MAC/IP Advertisement) routes carry a MAC address, optionally an IP, and the next-hop VTEP. They enable control-plane MAC learning and ARP suppression.

Question 21Data Center Networking Fundamentals

Which condition must be met for ECMP to install multiple next hops for a prefix?

  1. The paths must traverse different VLANs
  2. The paths must use different routing protocols
  3. The paths must have different administrative distances
  4. The paths must have equal cost and the same prefix length Correct answer.

Explanation

ECMP requires multiple routes to the same prefix with identical cost metrics; the router then installs all of them. Different administrative distances or metrics would make one path preferred instead.

Question 22Data Center Networking Fundamentals

A fabric uses VXLAN with a 1500-byte tenant MTU. What minimum underlay MTU is required to avoid fragmentation, assuming IPv4 outer headers with no additional options?

  1. 1550 bytes
  2. 9000 bytes
  3. 1500 bytes
  4. 1600 bytes Correct answer.

Explanation

VXLAN adds 8 bytes (VXLAN), 8 bytes (UDP), 20 bytes (outer IPv4), and 14 bytes (outer Ethernet), totaling about 50 bytes of overhead. An underlay MTU of at least 1550 is required, so 1600 is the safe minimum among the choices.

Question 23Data Center Networking Fundamentals

Why does a distributed anycast gateway improve east-west traffic efficiency compared with a centralized gateway?

  1. It compresses packet headers to reduce bandwidth
  2. It forces all traffic through a single spine for inspection
  3. It keeps the first-hop routing local to the source leaf, avoiding a hairpin to a central device Correct answer.
  4. It replaces the need for a routing protocol in the underlay

Explanation

With anycast gateway, every leaf can route for the subnet locally, so traffic does not need to detour to a central gateway before crossing the fabric. This reduces latency and spine load.

Question 24Data Center Networking Fundamentals

Which statement best explains why a routed underlay is preferred over a large Layer 2 domain in modern data centers?

  1. It increases the broadcast domain size
  2. It provides loop-free multipath forwarding and bounds failure domains Correct answer.
  3. It eliminates the need for IP addressing
  4. It removes the requirement for redundant links

Explanation

A routed underlay uses ECMP for active multipath and confines broadcast and failure domains to individual links. Large Layer 2 domains rely on STP, which blocks redundant paths and scales poorly.

Question 25Data Center Networking Fundamentals

Which protocol is typically used to build an IP-routed underlay in a modern data center spine-leaf fabric?

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

Explanation

BGP is widely used because it scales well, supports multipath, and provides policy control. STP, LACP, and VTP are Layer 2 protocols not used for routing the underlay.

Question 26Data Center Networking Fundamentals

In a VXLAN header, which field is used to identify the tenant network segment?

  1. VNI Correct answer.
  2. Outer UDP destination port
  3. Inner Ethernet source MAC
  4. Outer IP destination address

Explanation

The VXLAN Network Identifier (VNI) is a 24-bit field that uniquely identifies the tenant segment. The outer UDP port and IP addresses are used for reachability, not tenant identification.

Question 27Data Center Networking Fundamentals

Which statement describes the primary function of a VTEP in a VXLAN fabric?

  1. It encapsulates and decapsulates VXLAN frames at the edge of the overlay. Correct answer.
  2. It assigns IP addresses to servers in the tenant network.
  3. It acts as a route reflector for the underlay BGP sessions.
  4. It provides Layer 2 loop prevention across the underlay.

Explanation

A VTEP is the endpoint of a VXLAN tunnel; it adds or removes the VXLAN header as frames enter or leave the overlay. It does not perform DHCP, STP, or BGP route reflection by definition.

Question 28Data Center Networking Fundamentals

What is the purpose of an EVPN Type 3 route in a VXLAN fabric?

  1. To advertise an IP prefix for the underlay.
  2. To advertise a MAC address and its associated VNI.
  3. To advertise the presence of a VTEP and enable multicast replication for BUM traffic. Correct answer.
  4. To advertise a MAC/IP binding for ARP suppression.

Explanation

Type 3 routes are Inclusive Multicast Ethernet Tag routes that signal VTEP membership and are used for BUM traffic replication. Type 2 routes advertise MAC and MAC/IP bindings, and Type 5 routes advertise IP prefixes.

Question 29Data Center Networking Fundamentals

Which design principle is most characteristic of a spine-leaf fabric?

  1. Every leaf connects to every spine, and leaves do not connect to each other. Correct answer.
  2. Spines are connected only to core routers, not to leaves.
  3. Spines connect to each other in a full mesh to provide redundancy.
  4. Leaves connect to each other in a ring for loop-free Layer 2.

Explanation

A spine-leaf fabric uses a full mesh between leaves and spines, with leaves acting as access and spines as aggregation. Leaves do not interconnect, which keeps the topology simple and predictable.

Question 30Data Center Networking Fundamentals

What does a /32 prefix in a fabric underlay typically represent?

  1. A point-to-point link between two switches.
  2. A summary route for a leaf switch.
  3. A default route to the spine layer.
  4. A loopback address used as a router ID or tunnel endpoint. Correct answer.

Explanation

A /32 prefix is a host route, commonly assigned to a loopback interface for stable router IDs and VTEP addresses. Point-to-point links use /30 or /31, summaries use shorter prefixes, and default routes use /0.

Question 31Data Center Networking Fundamentals

Which statement about VXLAN is accurate?

  1. VXLAN provides a 24-bit VNI space, allowing more segments than traditional VLANs. Correct answer.
  2. VXLAN uses a 12-bit VNI field in the outer header.
  3. VXLAN requires STP to prevent loops in the overlay.
  4. VXLAN eliminates the need for an underlay routing protocol.

Explanation

VXLAN uses a 24-bit VNI, supporting up to 16 million segments, far exceeding the 12-bit VLAN ID space. It does not rely on STP in the overlay and still requires a routed underlay.

Question 32Data Center Networking Fundamentals

Which component is responsible for resolving the outer IP address of a remote VTEP in a VXLAN fabric?

  1. The anycast gateway MAC address.
  2. The overlay ARP table.
  3. The EVPN Type 2 route.
  4. The underlay routing protocol. Correct answer.

Explanation

The outer IP address belongs to the underlay, so it is resolved and forwarded using the underlay routing protocol. Overlay ARP and EVPN Type 2 routes deal with tenant addresses, not the outer VTEP IP.

Question 33Data Center Networking Fundamentals

A network engineer wants to verify that a leaf switch has formed BGP sessions with all spines in the underlay. Which command is most appropriate on an Arista switch?

  1. show ip bgp summary Correct answer.
  2. show interfaces status
  3. show vxlan vni
  4. show mac address-table

Explanation

The 'show ip bgp summary' command displays the state of BGP neighbors, including which sessions are established. The other commands show VXLAN VNIs, interface status, or MAC addresses, not BGP peering.

Question 34Data Center Networking Fundamentals

In a VXLAN fabric, which mechanism is used to prevent loops in the underlay?

  1. Spanning Tree Protocol.
  2. VXLAN network identifier isolation.
  3. Routing protocols with equal-cost multipath. Correct answer.
  4. Split horizon on the overlay.

Explanation

The underlay is a routed network, so loop prevention is handled by routing protocols and ECMP rather than STP. STP is not used in the underlay, and VNI isolation does not prevent physical loops.

Question 35Data Center Networking Fundamentals

Which statement best describes the role of an anycast gateway in a VXLAN fabric?

  1. It centralizes all inter-VLAN routing on a pair of spine switches.
  2. It assigns unique gateway IP addresses per leaf for each VLAN.
  3. It replaces the need for EVPN route advertisement.
  4. It provides a distributed default gateway with the same IP and MAC on every leaf. Correct answer.

Explanation

An anycast gateway uses the same IP and MAC address for a given VLAN on all leaves, allowing servers to route through their local leaf. This distributes routing and avoids tromboning traffic to a central gateway.

Question 36Data Center Networking Fundamentals

A leaf switch receives a frame for an unknown unicast destination in a VXLAN fabric with EVPN control plane. What does the leaf do?

  1. It encapsulates the frame and sends it to the anycast gateway.
  2. It floods the frame to all VTEPs in the VNI using multicast.
  3. It drops the frame because EVPN suppresses unknown unicast flooding. Correct answer.
  4. It sends the frame to the spine for centralized forwarding.

Explanation

With EVPN, MAC addresses are advertised via Type 2 routes, so unknown unicast flooding is typically disabled. The leaf drops the frame if the destination MAC is not known, avoiding unnecessary flooding.

Question 37Data Center Networking Fundamentals

Which hash input is commonly used by ECMP to ensure that a single TCP flow stays on one path?

  1. BGP router ID.
  2. Source and destination IP addresses and Layer 4 ports. Correct answer.
  3. VLAN ID and VNI.
  4. Source MAC address only.

Explanation

ECMP hashing typically uses a five-tuple (source/destination IP, source/destination port, and protocol) to distribute flows. Using only the source MAC or VLAN ID would not provide sufficient entropy and could cause polarization.

Question 38Data Center Networking Fundamentals

What is the effect of configuring a longer prefix length for a route in the fabric underlay?

  1. It reduces the number of ECMP next hops available.
  2. It becomes more specific and is preferred over shorter prefixes for matching destinations. Correct answer.
  3. It is automatically summarized by the underlay routing protocol.
  4. It increases the administrative distance of the route.

Explanation

Longer prefix lengths are more specific and are always preferred in longest-prefix-match routing. Summarization and ECMP are independent of prefix length, and administrative distance is a separate attribute.

Question 39Data Center Networking Fundamentals

In an EVPN fabric, which route type advertises a MAC address along with its associated IP address?

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

Explanation

Type 2 routes are MAC/IP advertisement routes that carry MAC and optionally IP bindings. Type 3 is for inclusive multicast, Type 5 is for IP prefixes, and Type 1 is for Ethernet auto-discovery.

Question 40Data Center Networking Fundamentals

A fabric uses VXLAN with a tenant MTU of 1500 bytes. What minimum underlay MTU is required to avoid fragmentation, assuming a VXLAN header of 50 bytes and outer IP/UDP headers of 28 bytes?

  1. 1528 bytes
  2. 1500 bytes
  3. 1578 bytes Correct answer.
  4. 1550 bytes

Explanation

The underlay MTU must accommodate the original 1500-byte frame plus the VXLAN, UDP, and outer IP headers. Adding 50 + 28 = 78 bytes to 1500 gives 1578 bytes.

Question 41Data Center Networking Fundamentals

In a VXLAN fabric, what is the purpose of the outer UDP destination port 4789?

  1. It identifies the destination VTEP.
  2. It identifies the source VTEP.
  3. It identifies VXLAN encapsulated traffic. Correct answer.
  4. It identifies the tenant VNI.

Explanation

UDP port 4789 is the IANA-assigned destination port for VXLAN, allowing receivers to recognize encapsulated frames. The VNI identifies the tenant, and IP addresses identify the VTEPs.

Question 42Data Center Networking Fundamentals

Which Arista feature allows a leaf switch to act as a VTEP and also perform Layer 3 routing for tenant networks?

  1. MLAG
  2. LANZ
  3. VXLAN routing Correct answer.
  4. sFlow

Explanation

VXLAN routing enables a leaf to decapsulate VXLAN frames and route between VNIs, often combined with an anycast gateway. MLAG, sFlow, and LANZ provide link aggregation, traffic sampling, and latency monitoring, respectively.

Question 43Data Center Networking Fundamentals

A network engineer observes that traffic between two leaves takes a longer path through a spine even though both leaves are connected to the same spine. What is the most likely cause?

  1. The VXLAN VNI is mismatched.
  2. The ECMP hash selected a path through a different spine due to flow characteristics. Correct answer.
  3. The underlay routing protocol has not converged.
  4. The anycast gateway is misconfigured.

Explanation

ECMP distributes flows across available equal-cost paths based on hashing, so a given flow may traverse any spine. This is normal behavior and not necessarily a fault.

Question 44Data Center Networking Fundamentals

Which field in the VXLAN header is used to carry the original Ethernet frame's VLAN tag?

  1. The inner Ethernet frame itself. Correct answer.
  2. The VNI field.
  3. The outer UDP checksum.
  4. The VXLAN header flags.

Explanation

VXLAN encapsulates the original Ethernet frame, including any VLAN tag, as the inner payload. The VXLAN header does not have a dedicated VLAN field; the VNI maps to a VLAN in the overlay.

Question 45Data Center Networking Fundamentals

In an EVPN fabric, which route type is used to advertise an IP prefix for inter-subnet routing?

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

Explanation

Type 5 routes are IP prefix routes used for inter-subnet routing and external reachability. Type 2 routes carry MAC/IP bindings, Type 3 is for inclusive multicast, and Type 4 is for Ethernet segment selection.

Question 46Data Center Networking Fundamentals

A fabric has 4 spines and 16 leaves, with every leaf connected to every spine. If each link is 100 Gbps and ECMP is used, what is the maximum available bandwidth between two leaves for a single flow?

  1. 1600 Gbps
  2. 200 Gbps
  3. 400 Gbps
  4. 100 Gbps Correct answer.

Explanation

A single flow is pinned to one path by ECMP hashing, so it can use at most the bandwidth of one link, which is 100 Gbps. Aggregate bandwidth across multiple flows could reach 400 Gbps, but not for a single flow.

Question 47Data Center Networking Fundamentals

Which statement about the underlay and overlay in a VXLAN fabric is correct?

  1. The underlay and overlay use the same routing table.
  2. The overlay must be a flat Layer 2 network.
  3. The underlay provides tenant MAC addresses, and the overlay provides IP routing.
  4. The underlay provides IP reachability between VTEPs, and the overlay provides Layer 2/Layer 3 services to tenants. Correct answer.

Explanation

The underlay is responsible for delivering encapsulated packets between VTEPs, while the overlay carries tenant traffic and services. They are independent layers with separate addressing and forwarding.

Question 48Data Center Networking Fundamentals

What is the primary benefit of using BGP EVPN as the control plane for VXLAN instead of flood-and-learn?

  1. It reduces BUM traffic flooding by distributing MAC/IP reachability information. Correct answer.
  2. It allows VLANs to span multiple data centers without configuration.
  3. It eliminates the need for an underlay routing protocol.
  4. It increases the VXLAN MTU.

Explanation

EVPN advertises MAC and IP bindings via BGP, so VTEPs know where destinations reside and can avoid flooding. This improves scalability and reduces unnecessary BUM traffic.

Question 49Data Center Networking Fundamentals

Which characteristic describes a Layer 3 leaf-spine design where each leaf peers with every spine?

  1. Leaf-to-leaf traffic is always hairpinned through the same spine pair
  2. Each leaf maintains a single uplink to one designated primary spine for all traffic
  3. Spines must run a spanning-tree protocol to block redundant paths
  4. Every leaf has an equal-cost path to every other leaf through any spine Correct answer.

Explanation

In a fully meshed Layer 3 leaf-spine fabric, every leaf connects to every spine, so a leaf reaches any remote leaf prefix via multiple equal-cost next hops and ECMP spreads flows across all available spines. This removes the need for spanning tree in the underlay because each link is a routed point-to-point segment.

Question 50Data Center Networking Fundamentals

A fabric uses an underlay MTU of 9214 bytes on all links. A tenant overlay encapsulates 1500-byte frames in VXLAN. Which statement explains why this underlay MTU is sufficient?

  1. The encapsulation overhead is small relative to the available headroom, so encapsulated frames fit without fragmentation Correct answer.
  2. The underlay MTU only matters for management traffic, not for tenant data
  3. VXLAN adds no bytes to the frame, so the underlay MTU only needs to match the tenant MTU
  4. The underlay MTU must equal the tenant MTU divided by the number of spines

Explanation

VXLAN encapsulation adds outer headers (outer Ethernet, IP, UDP, and VXLAN) on top of the original frame, so the underlay must carry the tenant frame plus that overhead. A 9214-byte underlay MTU leaves ample headroom for a 1500-byte tenant frame plus encapsulation, avoiding fragmentation.