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JNCIS-DC practice questions

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Question 1Data Center (domain details not enumerated in source; weights split evenly pending review)

In an EVPN-VXLAN data center fabric, which route type carries the MAC and IP address of a locally learned host so that remote leaf devices can populate their ARP/ND tables without flooding?

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

Explanation

EVPN Type 2 (MAC/IP advertisement) routes advertise both the MAC and the associated IP of a host, enabling remote VTEPs to learn ARP/ND entries and suppress ARP flooding. Type 3 handles inclusive multicast, Type 4 handles designated forwarder election, and Type 5 handles IP prefixes.

Question 2Data Center (domain details not enumerated in source; weights split evenly pending review)

Which Junos configuration hierarchy is used to define an EVPN-VXLAN fabric underlay routing instance on a QFX series switch?

  1. [edit switch-options vtep-source-interface]
  2. [edit routing-instances <name> protocols evpn] Correct answer.
  3. [edit vlans <name> vxlan]
  4. [edit protocols evpn]

Explanation

EVPN signaling is configured inside the routing instance that carries the overlay, under [edit routing-instances <name> protocols evpn]. The vtep-source-interface and vxlan statements supplement this but are not where EVPN protocols are enabled.

Question 3Data Center (domain details not enumerated in source; weights split evenly pending review)

In a Junos EVPN-VXLAN fabric using a spine-leaf design, what is the primary role of the spine layer?

  1. Act as the VTEP for all overlay traffic
  2. Provide IP underlay connectivity and route EVPN control-plane traffic between leaves Correct answer.
  3. Perform Layer 2 MAC learning for all attached hosts
  4. Terminate all storage traffic from compute nodes

Explanation

Spines act as the IP core, providing underlay reachability and forwarding EVPN/BGP control-plane traffic between leaf nodes. Leaves typically own the VTEP function and host MAC learning.

Question 4Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement correctly describes a VXLAN Network Identifier (VNI) in a data center fabric?

  1. A 24-bit identifier that maps to a VLAN and identifies an overlay segment Correct answer.
  2. A 16-bit identifier used for MPLS label stacking
  3. A 32-bit identifier used for VRF route targets
  4. A 12-bit identifier limited to 4094 usable segments

Explanation

The VNI is a 24-bit field in the VXLAN header, allowing roughly 16 million segments, and it maps to a VLAN at each VTEP. VLAN IDs are the 12-bit values that VXLAN extends beyond.

Question 5Data Center (domain details not enumerated in source; weights split evenly pending review)

Which protocol is used to carry EVPN address family routes between leaf and spine devices in a typical Junos IP fabric?

  1. OSPFv2
  2. MP-BGP Correct answer.
  3. LACP
  4. IS-IS

Explanation

EVPN is defined as a BGP address family, so MP-BGP (with the evpn NLRI) carries MAC/IP, multicast, and prefix routes across the fabric. OSPF and IS-IS can provide underlay reachability but do not carry EVPN NLRIs.

Question 6Data Center (domain details not enumerated in source; weights split evenly pending review)

In a Junos multihoming EVPN design, which mechanism prevents duplicate BUM traffic from being forwarded to a multihomed host across multiple leaf devices?

  1. Bidirectional forwarding detection
  2. BGP route reflection
  3. Graceful restart
  4. Designated forwarder election Correct answer.

Explanation

The designated forwarder (DF) election, signaled by EVPN Type 4 routes, ensures only one peering device forwards BUM traffic for a given Ethernet segment. This avoids duplicate packets reaching the multihomed host.

Question 7Data Center (domain details not enumerated in source; weights split evenly pending review)

Which Junos command displays the EVPN MAC table entries learned in a routing instance named DC1?

  1. show evpn mac-table instance DC1 Correct answer.
  2. show route table DC1.evpn.0
  3. show arp no-resolve instance DC1
  4. show ethernet-switching table instance DC1

Explanation

The 'show evpn mac-table instance DC1' command lists MAC addresses learned via EVPN for the specified routing instance, including local and remote entries. The route table command shows EVPN routes rather than the MAC table.

Question 8Data Center (domain details not enumerated in source; weights split evenly pending review)

A design requires that a VLAN be stretched across a VXLAN overlay while keeping the underlay IP-only. Which two Junos statements are needed to map the VLAN to a VNI? (Choose the best single answer.)

  1. vlan-id and vxlan vni under the VLAN definition Correct answer.
  2. vtep-source-interface and vlan-id under switch-options
  3. vni and route-target under the routing instance
  4. vlan-id and interface under the VLAN definition

Explanation

Under a VLAN definition, the vlan-id statement assigns the local VLAN and the vxlan vni statement maps it to the overlay VNI. Together they enable VLAN-to-VNI mapping on the VTEP.

Question 9Data Center (domain details not enumerated in source; weights split evenly pending review)

What is the purpose of a route target in an EVPN-VXLAN fabric with multiple tenants?

  1. To control which EVPN routes are imported into a given routing instance Correct answer.
  2. To identify the physical VTEP address for tunnel establishment
  3. To set the VNI value used for data-plane encapsulation
  4. To determine the designated forwarder for an Ethernet segment

Explanation

Route targets are BGP extended communities that determine import and export policy for EVPN routes, isolating tenant routing instances. They do not carry tunnel addresses or VNI values.

Question 10Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement about anycast gateway in a Junos EVPN-VXLAN fabric is correct?

  1. Anycast gateway disables ARP suppression on all leaf devices
  2. Anycast gateway requires a dedicated spine to host all gateway addresses
  3. The same gateway IP and MAC are configured on every leaf, allowing hosts to use a local default gateway Correct answer.
  4. A unique gateway MAC is required on each leaf to preserve routing symmetry

Explanation

Anycast gateway configures an identical IP and MAC for the distributed gateway on every leaf, so a host's default gateway is always local regardless of where it is attached. This supports seamless workload mobility.

Question 11Data Center (domain details not enumerated in source; weights split evenly pending review)

Which EVPN route type is used to advertise an IP prefix, such as a summarized subnet, into the overlay?

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

Explanation

Type 5 (IP prefix) routes advertise IP prefixes, including summarized or non-MAC-bearing subnets, into the EVPN overlay. Type 2 carries host MAC/IP bindings, Type 3 carries inclusive multicast, and Type 1 carries Ethernet auto-discovery.

Question 12Data Center (domain details not enumerated in source; weights split evenly pending review)

In an EVPN-VXLAN fabric, what does ARP suppression accomplish on a leaf VTEP?

  1. It forces ARP requests to be flooded to every VTEP
  2. It answers ARP requests locally using EVPN-learned IP-to-MAC bindings Correct answer.
  3. It converts ARP requests into DHCP requests
  4. It blocks all ARP traffic from entering the overlay

Explanation

With ARP suppression, the leaf answers ARP requests for known remote hosts from its EVPN-derived ARP table, reducing BUM flooding across the fabric. Unknown addresses may still be flooded.

Question 13Data Center (domain details not enumerated in source; weights split evenly pending review)

Which Junos feature allows a QFX switch to participate in an MC-LAG with a peer while also supporting EVPN multihoming?

  1. Ethernet segment identifier configuration Correct answer.
  2. Virtual chassis fabric
  3. IGMP snooping
  4. Spanning tree protocol

Explanation

An Ethernet segment identifier (ESI) identifies the multihomed segment shared by peer devices, enabling EVPN multihoming and DF election. MC-LAG can coexist but the ESI is the EVPN construct that defines the shared segment.

Question 14Data Center (domain details not enumerated in source; weights split evenly pending review)

What is the effect of configuring a VXLAN tunnel's source interface as a loopback address on a leaf device?

  1. The VTEP uses a stable, routable address independent of physical link state Correct answer.
  2. The VTEP uses the first physical uplink address for encapsulation
  3. The VTEP disables overlay encapsulation on that interface
  4. The VTEP requires a dedicated management interface for tunneling

Explanation

Using a loopback as the vtep-source-interface provides a stable VTEP address that remains reachable through the underlay even if individual links fail. This is standard practice in EVPN-VXLAN fabrics.

Question 15Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement about the underlay routing protocol in a Junos EVPN-VXLAN fabric is correct?

  1. It replaces MP-BGP for EVPN signaling
  2. It provides loopback-to-loopback reachability so VTEPs can build tunnels Correct answer.
  3. It assigns VNIs to VLANs automatically
  4. It carries tenant MAC addresses between leaves

Explanation

The underlay (for example OSPF or IS-IS) provides IP reachability between VTEP loopbacks, which is required to establish VXLAN tunnels. Tenant MAC and EVPN signaling are handled by the overlay MP-BGP session.

Question 16Data Center (domain details not enumerated in source; weights split evenly pending review)

A leaf device shows an EVPN Type 2 route for a remote host but no corresponding entry in the MAC table. Which action best helps diagnose the issue?

  1. Convert the underlay to static routes
  2. Reboot the remote leaf to clear stale routes
  3. Disable ARP suppression globally
  4. Check the route target import policy for the routing instance Correct answer.

Explanation

If the Type 2 route is not imported into the local instance due to a route target mismatch, the MAC entry will not be installed. Verifying the import policy and route targets is the correct diagnostic step.

Question 17Data Center (domain details not enumerated in source; weights split evenly pending review)

In an EVPN-VXLAN fabric, why is it recommended to use a unique VNI per tenant VLAN rather than reusing a single VNI across VLANs?

  1. VNI reuse forces the underlay to use MPLS
  2. Reusing a VNI merges distinct Layer 2 domains and can cause MAC and broadcast leakage between tenants Correct answer.
  3. VNI reuse disables anycast gateway functionality
  4. A single VNI cannot be encapsulated in VXLAN headers

Explanation

The VNI defines the Layer 2 overlay segment; reusing one VNI across different VLANs merges their broadcast domains, risking MAC learning conflicts and traffic leakage. Unique VNIs preserve tenant isolation.

Question 18Data Center (domain details not enumerated in source; weights split evenly pending review)

Which two conditions must be satisfied for a leaf to install a remote EVPN Type 2 route into its MAC table? (Choose the best single answer.)

  1. The route must be received over OSPF and the MAC must be locally learned
  2. The VNI must equal the local VLAN ID and the route must be Type 5
  3. The ESI must be zero and the route must originate from a spine
  4. The route target must match the local import policy and the next hop must be reachable Correct answer.

Explanation

A remote Type 2 route is imported only when its route target matches the instance's import policy and its next hop (the remote VTEP) is reachable through the underlay. Both conditions are required for MAC installation.

Question 19Data Center (domain details not enumerated in source; weights split evenly pending review)

What is the primary benefit of a collapsed spine-leaf design in a smaller data center?

  1. It eliminates the need for an underlay routing protocol
  2. It removes the requirement for EVPN signaling
  3. It forces all traffic through a single chassis
  4. It reduces the number of tiers while retaining IP-based leaf-spine forwarding Correct answer.

Explanation

A collapsed design merges tiers to reduce cabling and device count while preserving the leaf-spine forwarding model. The underlay and EVPN signaling are still required.

Question 20Data Center (domain details not enumerated in source; weights split evenly pending review)

Which Junos command verifies that a VXLAN tunnel to a remote VTEP is up and shows the associated VNI?

  1. show route table inet.0
  2. show chassis hardware
  3. show interfaces vtep Correct answer.
  4. show system uptime

Explanation

The 'show interfaces vtep' command displays the virtual tunnel endpoint interface, its state, and associated VXLAN tunnel information. Other commands listed do not show tunnel status.

Question 21Data Center (domain details not enumerated in source; weights split evenly pending review)

In a Junos EVPN configuration, what does the 'encapsulation vxlan' statement under a routing instance enable?

  1. GRE tunneling between spines
  2. VXLAN data-plane encapsulation for the overlay Correct answer.
  3. MPLS label allocation for the underlay
  4. IPsec encryption of EVPN routes

Explanation

The encapsulation vxlan statement enables VXLAN data-plane encapsulation for the routing instance's overlay traffic. It does not configure MPLS, GRE, or IPsec.

Question 22Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement best explains why BUM traffic replication in EVPN-VXLAN typically uses ingress replication or multicast?

  1. Because VNIs are limited to unicast frames
  2. Because the underlay cannot route multicast traffic
  3. Because EVPN disables all multicast forwarding
  4. Because VXLAN has no native broadcast mechanism across the overlay Correct answer.

Explanation

VXLAN does not provide native broadcast across the overlay, so BUM traffic must be replicated to interested VTEPs using ingress replication or underlay multicast. EVPN Type 3 routes signal the replication targets.

Question 23Data Center (domain details not enumerated in source; weights split evenly pending review)

A tenant requires Layer 3 isolation between two departments while sharing the same physical leaf pair. Which Junos construct provides this isolation in an EVPN-VXLAN fabric?

  1. A single routing instance with two VLANs
  2. A shared anycast gateway address
  3. A single VNI mapped to both departments
  4. Separate routing instances with distinct VRF route targets Correct answer.

Explanation

Separate routing instances (VRFs) with distinct route targets isolate Layer 3 reachability between departments while sharing the physical fabric. VLANs alone provide Layer 2 separation, not routed isolation.

Question 24Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement about the EVPN Type 3 route is correct?

  1. It advertises summarized IP prefixes
  2. It advertises the VTEPs interested in a given VNI for BUM replication Correct answer.
  3. It elects the designated forwarder
  4. It advertises host MAC and IP bindings

Explanation

The Type 3 inclusive multicast Ethernet tag route signals which VTEPs should receive BUM traffic for a VNI. Host bindings are Type 2, DF election is Type 4, and prefix advertisement is Type 5.

Question 25Data Center (domain details not enumerated in source; weights split evenly pending review)

Which factor most directly determines the maximum number of VXLAN segments a fabric can support?

  1. The BGP autonomous system number
  2. The 12-bit VLAN ID space
  3. The number of physical spines
  4. The 24-bit VNI space Correct answer.

Explanation

VXLAN uses a 24-bit VNI, allowing approximately 16 million segments, which is the primary scaling limit. VLAN IDs are limited to 12 bits and spines or ASNs do not define segment count.

Question 26Data Center (domain details not enumerated in source; weights split evenly pending review)

On a Junos QFX Series switch, which statement correctly describes the role of an ESI in an EVPN multihomed design?

  1. It is the route target that scopes EVPN routes to a single tenant VRF.
  2. It is the loopback address used as the VXLAN tunnel source on each leaf device.
  3. It is the VNI-to-VLAN mapping value carried inside the VXLAN header.
  4. It is a globally unique value assigned to a multihomed Ethernet segment so all VTEPs can identify the same segment. Correct answer.

Explanation

An Ethernet Segment Identifier is a 10-byte value that uniquely identifies a multihomed segment spanning several leaf devices. Every PE attached to that segment advertises the same ESI in its EVPN routes, which lets remote VTEPs treat the links as one logical segment for aliasing and designated-forwarder election.

Question 27Data Center (domain details not enumerated in source; weights split evenly pending review)

A design uses a QFX5100 leaf pair running Junos with MC-LAG toward servers. Which statement describes a correct MC-LAG requirement on the inter-chassis link?

  1. The ICL should be a LAG that carries the inter-chassis control protocol traffic and data for orphan ports. Correct answer.
  2. The ICL must be routed with OSPF enabled over it.
  3. The ICL must be a single member link with no LACP configured.
  4. The ICL must be placed in the same VLAN as the server-facing LAG.

Explanation

The inter-chassis link is normally configured as a Link Aggregation Group that carries ICCP control traffic and forwards traffic for orphaned links. It must be a LAG rather than a single link so it survives a member failure, and it is kept separate from server-facing VLANs.

Question 28Data Center (domain details not enumerated in source; weights split evenly pending review)

Which Junos configuration element on a QFX switch enables a VLAN to be extended over a VXLAN overlay?

  1. A vtep-source statement under the switch-options hierarchy.
  2. A vxlan statement under the protocols evpn hierarchy with a VNI mapping.
  3. An irb interface with a VXLAN encapsulation configured.
  4. A virtual-switch routing instance containing the VLAN and a VXLAN encapsulation. Correct answer.

Explanation

In Junos, VXLAN bridging is configured inside a virtual-switch type routing instance, where the VLAN is associated with a VNI and the instance uses VXLAN encapsulation. The routing instance scopes the bridging domain and the VNI mapping together.

Question 29Data Center (domain details not enumerated in source; weights split evenly pending review)

An engineer wants a Junos QFX switch to act as a Layer 3 VXLAN gateway for a tenant. Which interface type must be configured to provide the distributed anycast gateway address?

  1. A physical trunk interface in the tenant VLAN.
  2. An IRB interface in the tenant routing instance. Correct answer.
  3. A VTEP source interface in the default instance.
  4. A loopback interface in the default instance.

Explanation

The integrated routing and bridging interface carries the gateway IP and MAC for the subnet and is placed in the tenant's routing instance. When the same IRB address and MAC are configured on every leaf, hosts see a consistent anycast gateway regardless of which leaf they attach to.

Question 30Data Center (domain details not enumerated in source; weights split evenly pending review)

Which Junos command displays the VXLAN network identifiers and their associated VLANs for a virtual-switch instance named DC1?

  1. show vlans instance DC1 detail
  2. show vxlan tunnel instance DC1
  3. show ethernet-switching table instance DC1
  4. show evpn instance DC1 extensive Correct answer.

Explanation

The show evpn instance command reports the EVPN instance state, including the VNI and the VLANs mapped to it, and the extensive form adds per-instance detail. It is the direct way to confirm the VLAN-to-VNI binding in Junos.

Question 31Data Center (domain details not enumerated in source; weights split evenly pending review)

In a Junos EVPN-VXLAN fabric, what does the designated forwarder election accomplish for a multihomed Ethernet segment?

  1. It selects which PE originates the Type 5 prefix routes for the tenant.
  2. It selects which PE becomes the route reflector for the fabric.
  3. It selects which PE forwards broadcast, unknown unicast, and multicast traffic toward the segment. Correct answer.
  4. It selects which PE owns the anycast gateway MAC address.

Explanation

DF election chooses one PE per segment to forward BUM traffic toward the multihomed hosts, preventing duplicate copies from reaching them. The other PEs on the segment stay in a backup role and can take over if the DF fails.

Question 32Data Center (domain details not enumerated in source; weights split evenly pending review)

A fabric uses EVPN with ingress replication for BUM traffic. Which statement describes how a leaf learns the set of remote VTEPs to which it must replicate?

  1. It learns them from the Type 5 prefix routes received for each tenant.
  2. It learns them from the Type 2 MAC routes received for each tenant.
  3. It learns them from Type 3 inclusive multicast routes received from other VTEPs. Correct answer.
  4. It learns them from the underlay OSPF database.

Explanation

Type 3 inclusive multicast Ethernet auto-discovery routes signal VTEP membership in a VNI, and each receiving leaf builds its replication list from them. Ingress replication then sends one copy of each BUM frame to every listed VTEP.

Question 33Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement describes the function of the EVPN Type 1 route in a Junos EVPN deployment?

  1. It advertises a MAC and IP binding for an attached host.
  2. It advertises an Ethernet auto-discovery route per ESI and per EVI to support fast convergence and aliasing. Correct answer.
  3. It advertises an IP prefix for a tenant subnet.
  4. It advertises an inclusive multicast tree for a VNI.

Explanation

The Ethernet auto-discovery route carries an ESI and an Ethernet tag, allowing remote PEs to learn segment membership and to build aliasing and fast-convergence behavior. It is sent per ESI per EVI and is fundamental to multihoming convergence.

Question 34Data Center (domain details not enumerated in source; weights split evenly pending review)

An engineer must verify which ESI a local interface has been assigned in a Junos EVPN multihoming configuration. Which command output shows this mapping directly?

  1. show interfaces terse
  2. show evpn ethernet-segment Correct answer.
  3. show route table evpn.evpn.0
  4. show chassis forwarding

Explanation

The show evpn ethernet-segment command lists configured Ethernet segments, their ESI values, and the interfaces associated with each. It is the most direct way to confirm that the intended interface carries the intended ESI.

Question 35Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement about a Junos Virtual Chassis Fabric or spine-leaf underlay using BGP is correct?

  1. Each leaf peers with each spine, and the spines do not need to peer with each other for leaf-to-leaf reachability. Correct answer.
  2. BGP must be replaced by IS-IS because EVPN requires an IGP underlay.
  3. iBGP must be used because eBGP cannot carry EVPN address family routes.
  4. eBGP peering between leaf and spine requires a full mesh among all leaves.

Explanation

A standard IP fabric underlay peers every leaf with every spine, and BGP multipath provides leaf-to-leaf reachability through the spines. The spines act as BGP next-hop relays and do not need direct peering among themselves.

Question 36Data Center (domain details not enumerated in source; weights split evenly pending review)

A QFX leaf is configured with a VTEP source interface of lo0.0. Which additional requirement must be met for VXLAN tunnels to establish with remote leaves?

  1. The lo0.0 address must be reachable through the underlay routing table. Correct answer.
  2. The lo0.0 address must be in the same subnet as every remote VTEP.
  3. The lo0.0 address must be advertised into EVPN as a Type 5 route.
  4. The lo0.0 interface must be bound to a physical port.

Explanation

VXLAN encapsulates inner frames in UDP/IP packets sent to the remote VTEP address, so the local and remote loopbacks must be routable through the underlay. Advertising the loopback into the underlay routing protocol provides that reachability.

Question 37Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement correctly describes how a Junos device handles a frame destined to a MAC address that is present in the local Ethernet switching table and also learned remotely through EVPN?

  1. The device floods the frame to both paths to guarantee delivery.
  2. The remote EVPN entry always takes precedence and the frame is tunneled.
  3. The local entry always takes precedence and the frame is bridged locally. Correct answer.
  4. The device drops the frame because of the conflicting entries.

Explanation

Junos prefers a locally learned MAC entry over a remote EVPN learned entry for the same address, so traffic to a locally attached host stays on the local bridge domain. This avoids tromboning traffic through the overlay when the destination is directly reachable.

Question 38Data Center (domain details not enumerated in source; weights split evenly pending review)

Which Junos feature allows a pair of QFX switches to present a single control plane to attached servers while each switch maintains an independent forwarding plane?

  1. MC-LAG Correct answer.
  2. Virtual Chassis Fabric
  3. Virtual Chassis
  4. EVPN multihoming with ESI

Explanation

MC-LAG lets two independent switches share a LAG toward a server without merging their control planes, so each keeps separate management and forwarding. Virtual Chassis instead merges the switches into one logical control plane.

Question 39Data Center (domain details not enumerated in source; weights split evenly pending review)

A tenant requires that traffic between two VLANs in the same EVPN-VXLAN fabric be routed at the leaf where the source host attaches. Which Junos design accomplishes this?

  1. A distributed anycast gateway with an IRB interface for each VLAN on every leaf. Correct answer.
  2. A centralized gateway with all IRB interfaces on a single spine.
  3. A routed subinterface on each server-facing port.
  4. A Layer 2 stretch of both VLANs to a firewall for inter-VLAN routing.

Explanation

A distributed anycast gateway places an IRB for each VLAN on every leaf with the same IP and MAC, so each leaf routes locally and the packet crosses the overlay only once. This avoids the hairpinning and scale limits of a centralized gateway.

Question 40Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement about the EVPN Type 4 route is correct?

  1. It advertises the ESI and the originating PE IP address to enable designated forwarder election. Correct answer.
  2. It advertises an IP prefix for a tenant subnet.
  3. It advertises a MAC address learned on a multihomed segment.
  4. It advertises the VNI membership for BUM replication.

Explanation

The Ethernet segment route carries the ESI and the originating PE address, and PEs attached to the same segment use it to discover each other. That discovery is the basis for DF election on the segment.

Question 41Data Center (domain details not enumerated in source; weights split evenly pending review)

An engineer needs to confirm that a Junos leaf has received EVPN routes from a specific remote VTEP. Which command is most appropriate?

  1. show bgp neighbor
  2. show route table evpn.evpn.0 detail Correct answer.
  3. show configuration protocols evpn
  4. show ethernet-switching interface

Explanation

The EVPN routing table holds the received and locally originated EVPN routes, and the detail form shows attributes such as the originating next hop. Filtering that output by the remote VTEP address confirms what was received from it.

Question 42Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement explains why a VXLAN VNI is typically mapped to a single VLAN within a virtual-switch instance in Junos?

  1. A VNI can only be configured on a spine device.
  2. The VNI is used only for routing between VRFs.
  3. The VNI must match the VLAN ID numerically for the encapsulation to work.
  4. The VNI identifies the Layer 2 bridge domain, so mapping multiple VLANs to one VNI would merge their broadcast domains. Correct answer.

Explanation

A VNI defines one Layer 2 segment across the overlay, so each VNI corresponds to one bridge domain. Mapping several VLANs to the same VNI would combine their broadcast domains and break tenant isolation.

Question 43Data Center (domain details not enumerated in source; weights split evenly pending review)

Which Junos statement enables a routing instance to signal EVPN routes for its local Ethernet segments?

  1. protocols evpn under the routing instance Correct answer.
  2. ethernet-switching-options evpn under the routing instance
  3. protocols bgp with the evpn-nlri family under the routing instance
  4. forwarding-options evpn under the routing instance

Explanation

The protocols evpn stanza inside the routing instance turns on EVPN signaling for that instance, including the local VNI and Ethernet segment advertisements. BGP transport is configured separately and carries the resulting routes.

Question 44Data Center (domain details not enumerated in source; weights split evenly pending review)

A leaf in a Junos EVPN-VXLAN fabric must route traffic between two VNIs in the same tenant. Which configuration is required on that leaf?

  1. A virtual-switch instance with both VLANs and no routing instance.
  2. Two separate virtual-switch instances with no IRB interfaces.
  3. A default-instance IRB shared with all tenants.
  4. A single virtual-switch instance containing both VLANs and an IRB in a tenant VRF. Correct answer.

Explanation

Inter-VNI routing requires the VLANs to be bridged in a virtual-switch instance and an IRB interface placed in the tenant's routing instance to provide the gateway. The VRF then holds the routes that let the leaf route between the two subnets.

Question 45Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement about the use of a route reflector in an EVPN fabric control plane is correct?

  1. It assigns VNIs to VLANs on each leaf.
  2. It reduces the number of BGP sessions by reflecting EVPN routes between leaves. Correct answer.
  3. It replaces the need for a VXLAN data plane.
  4. It elects the designated forwarder for each Ethernet segment.

Explanation

A route reflector centralizes BGP peering so each leaf needs sessions only to the reflectors rather than to every other leaf. It forwards EVPN routes among clients without changing the data plane or the VNI configuration.

Question 46Data Center (domain details not enumerated in source; weights split evenly pending review)

Which Junos command shows the VXLAN encapsulation and decapsulation statistics for a VTEP?

  1. show vxlan statistics Correct answer.
  2. show evpn statistics
  3. show ethernet-switching statistics
  4. show interfaces vtep

Explanation

The show vxlan statistics command reports counters for encapsulated and decapsulated packets on the VTEP. These counters help confirm that overlay traffic is being tunneled and received as expected.

Question 47Data Center (domain details not enumerated in source; weights split evenly pending review)

A design requires that a Junos QFX leaf support both EVPN-VXLAN overlay and traditional VLAN trunking to a legacy server. Which approach is valid?

  1. Place all VLANs in the same virtual-switch instance and map the legacy VLAN to a VNI.
  2. Place the legacy VLAN in a standard VLAN with trunk ports while VXLAN VLANs live in a virtual-switch instance. Correct answer.
  3. Use MC-LAG instead of EVPN for the legacy server.
  4. Disable EVPN on the leaf so that only trunking works.

Explanation

Junos allows standard VLANs and virtual-switch instances to coexist, so legacy Layer 2 trunking can continue alongside the VXLAN overlay. The legacy VLAN stays local and is not mapped to a VNI unless it must be stretched.

Question 48Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement about the VXLAN UDP destination port used by Junos VTEPs is correct?

  1. It is dynamically negotiated per tunnel through BGP.
  2. It is carried only in the outer IP header and is not inspected by VTEPs.
  3. It is always 4789 by default, and it must match on all VTEPs in the fabric. Correct answer.
  4. It must be 6635 for EVPN to function.

Explanation

Junos VTEPs use UDP destination port 4789 for VXLAN encapsulation, and all VTEPs in the fabric must agree on the port for tunnels to be decapsulated. The port is part of the outer UDP header and is checked on receipt.

Question 49Data Center (domain details not enumerated in source; weights split evenly pending review)

An engineer observes that a remote host's MAC address appears in the EVPN route table but not in the local Ethernet switching table. Which condition most likely explains this?

  1. The local leaf has no IRB interface configured.
  2. The local leaf has not imported the route because the route target does not match the local VRF. Correct answer.
  3. The remote VTEP is using a different VXLAN UDP port.
  4. The underlay BGP session is using IPv6.

Explanation

A Type 2 route is only usable if its route target matches the import policy of the local EVPN instance or VRF. A mismatch leaves the route in the table without installing the MAC into the local bridging table.

Question 50Data Center (domain details not enumerated in source; weights split evenly pending review)

Which statement about the use of a loopback interface as the BGP router ID on a Junos EVPN leaf is correct?

  1. The router ID is only relevant for IPv6 BGP sessions.
  2. The router ID must be the same on all leaves to form EVPN sessions.
  3. The router ID must match the VTEP source address for tunnels to form.
  4. A unique stable loopback address provides a consistent router ID that survives physical link failures. Correct answer.

Explanation

A loopback address stays up as long as the device is reachable, so using it as the router ID keeps BGP identity stable across physical link changes. Each leaf must have a unique router ID for BGP sessions to establish correctly.