JNCIP-ENT EVPN Practice Test 2 — 15 Questions

Question 1

You are troubleshooting an EVPN-VXLAN environment where a Juniper QFX Series switch is configured as a VTEP. You notice that MAC addresses learned from the local access ports are not being advertised to remote VTEPs via BGP EVPN. The BGP session is established, and Type-3 routes are being exchanged. Which action should you take to resolve this issue?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Check that the BGP EVPN NLRI is enabled for the address family and that the local MAC addresses are being learned in the EVPN instance's MAC table.. Type-2 routes are generated when MAC addresses are learned in the EVPN instance's MAC-VRF table. If local MACs are not advertised, the first step is to verify that MAC learning is happening and that the BGP EVPN NLRI is enabled for the address family. Without MAC learning, no Type-2 routes will be generated, regardless of other configurations.

Answer

Ensure that the remote VTEP's loopback address is reachable via the underlay network and that the VXLAN tunnel is up.

Answer

Confirm that the EVPN instance is configured with a route distinguisher and route target that match the remote VTEPs.

Answer

Verify that the VXLAN tunnel interface is included in the EVPN routing instance and that the MAC-VRF instance is correctly associated with the VLAN.

Question 2

You are troubleshooting an EVPN-VXLAN fabric on Juniper switches. A leaf switch is configured with an EVPN instance and a VXLAN tunnel interface. Hosts on this leaf cannot communicate with hosts on a remote leaf, even though BGP EVPN sessions are established and Type 2 routes are exchanged. What is the most likely cause of the connectivity failure?

Accepted Answer

The VXLAN tunnel interface is not bound to the EVPN instance.. The most likely cause is that the VXLAN tunnel interface is not bound to the EVPN instance. Without this binding, the switch cannot encapsulate traffic into VXLAN, even though control plane routes are present. BGP sessions and route exchange confirm that the control plane is healthy, so the failure is in the data plane. Other options would affect control plane operation, which is already working.

Answer

The Type 2 routes are not being imported due to a route target mismatch.

Answer

The BGP EVPN session is using the wrong address family.

Answer

The remote VTEP IP address is not reachable.

Question 3

You are configuring an EVPN-VXLAN fabric on Juniper switches. You want to enable inter-subnet routing using a distributed anycast gateway. Which TWO statements are true about this configuration? (Choose two.)

Accepted Answer

Type 2 routes are used to advertise the gateway's IP-to-MAC binding.. In a distributed anycast gateway, all leaf switches share the same gateway IP and MAC address, and they advertise this binding via Type 2 routes. This allows each leaf to perform inter-subnet routing locally for its attached hosts, optimizing traffic paths. The gateway MAC is not unique per leaf, and routing is not centralized at spines.

Answer

The gateway MAC address must be manually configured on each leaf switch and must be different.

Answer

Each leaf switch advertises its own unique gateway MAC address via Type 2 routes.

Answer

Inter-subnet routing is performed only at the spine switches.

Question 4

You are configuring an EVPN-VXLAN fabric on Juniper devices. You need to ensure that the underlay network can transport VXLAN-encapsulated packets between leaf switches. The underlay uses an IP fabric with OSPF as the IGP. Which statement describes the required MTU configuration on the underlay interfaces to support VXLAN traffic without fragmentation?

Accepted Answer

The underlay MTU must be set to at least 1600 bytes to prevent fragmentation of VXLAN-encapsulated frames.. VXLAN encapsulation adds 50 bytes of overhead to the original Ethernet frame. To avoid fragmentation, the underlay MTU must be increased to accommodate this overhead. A minimum of 1550 bytes is required for a 1500-byte payload, but a value of 1600 bytes is commonly recommended to provide additional headroom. This ensures that VXLAN-encapsulated packets are forwarded without fragmentation, maintaining performance and reliability.

Answer

The underlay MTU must be set to exactly 9000 bytes to support VXLAN jumbo frames.

Answer

The underlay MTU must be set to at least 1500 bytes to accommodate the original Ethernet frame.

Answer

The underlay MTU must be increased to at least 1550 bytes to account for VXLAN, UDP, and IP headers.

Question 5

An administrator is deploying EVPN multi-homing with all-active mode on an MX Series router. Which configuration element uniquely identifies the provider edge (PE) router's attachment circuit to an Ethernet segment?

Accepted Answer

Ethernet Segment Identifier (ESI). The Ethernet Segment Identifier (ESI) is a 10-octet unique identifier configured under the interface or access link to identify an Ethernet segment for multi-homing.

Answer

Route Distinguisher (RD)

Answer

Ethernet Tag ID

Answer

ESI Label Extended Community

Question 6

An administrator notices that broadcast, unknown unicast, and multicast (BUM) traffic sent from a local host is looping back to the originating multi-homed PE when using an all-active Ethernet segment. Which mechanism prevents this loop in EVPN?

Accepted Answer

EVPN Split Horizon filtering using ESI labels. EVPN uses Split Horizon filtering via the ESI Label Extended Community or local split-horizon checks to ensure that BUM traffic received from a remote PE on a shared Ethernet segment is not sent back out to the same segment.

Answer

BGP Best Path Selection algorithm

Answer

Designated Forwarder (DF) election

Answer

Spanning Tree Protocol (STP) root guard

Question 7

Which specific EVPN route type is responsible for carrying IP prefix routes, often used for inter-subnet forwarding in an IP-VRF-to-EVPN integration scenario?

Accepted Answer

Route Type 5. EVPN Route Type 5 is the IP Prefix Route, which allows the advertisement of IP prefixes (host or subnet routes) independently of MAC addresses, facilitating integrated routing and bridging (IRB) and inter-subnet forwarding.

Answer

Route Type 3

Answer

Route Type 2

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Route Type 1

Question 8

When configuring centralized gateway or distributed gateway routing models in an EVPN-VXLAN environment, how does a distributed gateway using Integrated Routing and Bridging (IRB) interfaces operate regarding default gateway functionality?

Accepted Answer

All leaf nodes act as default gateways using the same virtual MAC and IP address, terminating traffic locally.. In a distributed gateway model, every leaf/VTEP acts as the default gateway for its directly attached subnets, using anycast MAC and IP addresses so hosts can send traffic to their local VTEP regardless of which leaf they connect to.

Answer

Routing is disabled on leaf nodes, requiring all packets to be tunneled to spine nodes for L3 lookup.

Answer

A single designated MX core router handles all inter-subnet routing via centralized IRB interfaces.

Answer

Hosts must run VRRP between leaf nodes to dynamically elect a single active gateway.

Question 9

An engineer is verifying MAC learning behavior in an EVPN instance. A remote host's MAC address is learned via BGP Type 2 routes, but when the local host sends traffic to it, the packet drops. The engineer runs 'show route table bgp.evpn.0' and sees the route. What is the most likely reason the packet is dropping in the data plane?

Accepted Answer

The data-plane VNI mapping or tunnel next-hop resolution is incomplete.. Even if the control plane has learned the EVPN Type 2 route, if the data plane tunnel encapsulation (such as a missing VNI mapping or incomplete VXLAN next-hop resolution) is misconfigured, data plane forwarding will fail.

Answer

Type-4 routes have not been exchanged yet.

Answer

The BGP route target import policy is rejecting the route.

Answer

The local router's BGP router ID is misconfigured.

Question 10

Which BGP address family must be enabled under the BGP neighbor configuration to exchange EVPN routes between PE routers?

Accepted Answer

evpn signaling (or l2vpn evpn). To exchange EVPN routing information, the 'evpn signaling' or 'l2vpn evpn' address family must be configured under the BGP protocol hierarchy and neighbor sessions.

Answer

inet-unicast

Answer

vpls-signaling

Answer

iso-unicast

Question 11

Which Junos configuration hierarchy is used to define an EVPN routing instance of type 'evpn'?

Accepted Answer

routing-instances instance-type evpn. In Junos OS, EVPN instances are defined under 'routing-instances instance-type evpn'.

Answer

bridge-domains <name> evpn

Answer

protocols evpn

Answer

interfaces xe-0/0/0 unit 0 family evpn

Question 12

You are integrating an EVPN-VXLAN fabric with an existing MPLS L3VPN backbone using a data center gateway. Which route type allows seamless translation and communication of prefix routes between the EVPN instance and the IP-VRF MPLS VPN backbone?

Accepted Answer

Route Type 5. EVPN Route Type 5 (IP Prefix Route) permits the advertising of IP prefixes that can be easily imported into IP-VRFs, bridging EVPN and classical MPLS L3VPN domains.

Answer

Route Type 3

Answer

Route Type 1

Answer

Route Type 2

Question 13

An engineer is troubleshooting a newly configured EVPN-VXLAN multi-homed setup where the Designated Forwarder (DF) is constantly toggling between two PE routers. What is the most likely cause of this DF churn?

Accepted Answer

Mismatched Ethernet Segment Identifiers (ESIs) or unstable BGP connectivity between PEs.. DF churn typically occurs when BGP sessions or reachability between the PE routers flapping, or when the timers (such as wait-for-timer) are misconfigured, causing conflicting DF election states.

Answer

Incorrect MAC mobility sequence numbers.

Answer

Exceeding the maximum MAC address table limit.

Answer

Using VXLAN instead of MPLS data plane encapsulation.

Question 14

Which EVPN route type is responsible for advertising MAC addresses combined with IP addresses (MAC/IP Advertisement Route)?

Accepted Answer

Route Type 2. Route Type 2 is the MAC/IP Advertisement Route, which carries a MAC address and optionally an IP address, facilitating both L2 bridging and L3 host routing.

Answer

Route Type 3

Answer

Route Type 4

Answer

Route Type 1

Question 15

You are designing an EVPN network with active-active multi-homing. A host sends traffic to a multi-homed PE. The PE receives the traffic on a designated link. How does EVPN suppress unnecessary flooding across the core for unknown unicast traffic originating from a multi-homed site?

Accepted Answer

By dynamically learning MAC addresses via control-plane Type 2 routes, turning unknown unicast into known unicast.. EVPN suppresses unknown unicast flooding by performing MAC learning via control-plane advertisement (Type 2 routes) upon first contact, so subsequent traffic is unicast-forwarded rather than flooded.

Answer

By utilizing Spanning Tree Protocol to block redundant ports across the core.

Answer

By dropping all packets with unknown destination MAC addresses at the ingress leaf.

Answer

By enforcing ingress replication drop filters on Type 3 routes.