JNCIP-ENT EVPN — Timed 20 Questions

Question 1

You are troubleshooting a suboptimal traffic forwarding issue in an EVPN-VXLAN fabric with multi-homed devices. Traffic destined for a multi-homed server is being sent to only one of the PEs despite all-active mode being configured. Which EVPN route type and mechanism are responsible for enabling load balancing across all available PEs attached to the same Ethernet segment?

20 minute time limit — choose an answer to begin.

Accepted Answer

Route Type 1 (Ethernet Auto-Discovery per EVI). Type 1 Ethernet A-D routes per EVI are used for multi-homing aliasing, allowing PEs that do not learn a specific MAC address locally to still load-balance traffic to that MAC across all PEs advertising the ESI via Type 1 routes.

Answer

Route Type 2 with MAC mobility extended community

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Route Type 4 (Ethernet Segment Route)

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Route Type 3 (Inclusive Multicast)

Question 2

You are configuring a Junos EVPN-VXLAN environment where Type-3 (Inclusive Multicast Ethernet Tag) routes are being exchanged. A remote MX router is failing to establish ingress replication tunnels because it does not import the Type-3 route. Which configuration statement under the routing-instance is missing or misconfigured?

Accepted Answer

route-target import. EVPN Type-3 routes carry the Inclusive Multicast Ethernet Tag and rely on route targets for import and export. If the import route-target does not match the advertising router's export route-target, the tunnel endpoints are not dynamically bound.

Answer

no-normalization

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multicast-snooping

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vtep-source-interface lo0.0

Question 3

During a maintenance window, an administrator needs to manually force a Designated Forwarder (DF) role change on a multi-homed Ethernet segment for an EVPN instance. Which parameter must be adjusted to influence the DF election algorithm in Junos OS?

Accepted Answer

Ethernet segment preference value. Junos OS allows influencing the DF election by adjusting the interface preference or local preference values associated with the Ethernet Segment, altering how the DF election algorithm selects the forwarder.

Answer

BGP AS path prepending

Answer

Route Distinguisher value

Answer

Router ID of the BGP speaker

Question 4

When configuring VXLAN data plane encapsulation inside an EVPN routing instance on Junos OS, which logical interface type must be bound to the bridge domain to provide VXLAN VNI mapping?

Accepted Answer

VLAN interface (vlan statement with vni). In Junos OS, VXLAN encapsulation is configured using logical tunnel interfaces or integrated routing and bridging (IRB) interfaces mapped via a vni statement under the bridge-domains hierarchy.

Answer

lo0.0

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gre0

Answer

fxp0

Question 5

An engineer is troubleshooting EVPN type 2 routes between two MX Series routers and notices that MAC addresses learned locally are not being advertised to the remote VTEP. Which command should the engineer use to verify that the EVPN instance is actively generating and exporting MAC-VRF routes?

Accepted Answer

show route advertising-protocol bgp <neighbor-ip>. The 'show route advertising-protocol bgp' command allows an engineer to verify which routes (including EVPN type 2 MAC/IP routes) are being advertised to a specific BGP peer or peer group for an EVPN routing instance.

Answer

show bridge mac-table

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show bgp summary

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show evpn database

Question 6

An enterprise network architect is designing an EVPN-VXLAN fabric and wants to ensure that MAC address churn (frequent moving of a MAC between ports) does not destabilize the control plane. Which feature should be enabled in the EVPN instance?

Accepted Answer

MAC limit and MAC mobility sequence numbering. MAC mobility features, including MAC move detection and sticky MAC or suppression mechanisms, protect the EVPN control plane from frequent MAC moves by incrementing sequence numbers and applying penalties if movement thresholds are exceeded.

Answer

Spanning Tree BPDU protection

Answer

Fast-reroute backup paths

Answer

BGP route flap damping

Question 7

Which EVPN route type is known as the Ethernet Segment Route and is advertised by a PE router to signal its connectivity to a multi-homed Ethernet segment?

Accepted Answer

Route Type 4. EVPN Route Type 4 is the Ethernet Segment Route, used for discovering other PEs attached to the same Ethernet segment and executing the Designated Forwarder (DF) election.

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Route Type 2

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Route Type 3

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Route Type 1

Question 8

An administrator wishes to configure VXLAN data plane encapsulation on an MX Series router with an EVPN instance. Which statement under the routing-instances hierarchy defines the local VTEP source interface?

Accepted Answer

vtep-source-interface lo0.0;. In Junos OS, the VXLAN source interface is defined using the 'vtep-source-interface' statement under the EVPN routing instance or switch-options hierarchy.

Answer

encapsulation-source-interface fxp0.0;

Answer

vxlan-source-ip lo0.0;

Answer

tunnel-source loopback 0;

Question 9

You are troubleshooting a scenario where an MX Series router running an EVPN-VXLAN instance receives Type-2 routes from a remote PE, but the local data plane fails to install the forwarding entries because of a mismatch in encapsulation types. Where is the encapsulation type for VXLAN defined within a Junos EVPN instance?

Accepted Answer

routing-instances <name> instance-type evpn; ... encapsulation vxlan;. In Junos OS, the encapsulation for the routing instance or switch options is defined using the 'encapsulation vxlan' statement under the routing-instance or switch-options hierarchy.

Answer

protocols bgp group <name> family evpn encapsulation vxlan

Answer

interfaces lo0.0 family vxlan

Answer

bridge-domains vni encapsulation mpls

Question 10

Which TWO of the following characteristics apply to EVPN Route Type 3 (Inclusive Multicast Ethernet Tag Route)? (Choose two)

Accepted Answer

It carries the originating router's IP address and an Ethernet Tag/VNI identifier.. Route Type 3 routes are used to construct the multicast/broadcast distribution tree using ingress replication (head-end replication) by advertising the PE's IP address and Ethernet tag/VNI.

Answer

It advertises host IP prefixes for inter-subnet routing.

Answer

It dynamically triggers MAC mobility sequence number increments.

Answer

It performs Designated Forwarder election on multi-homed links.

Question 11

Which TWO statements describe characteristics of EVPN All-Active Multi-Homing compared to Single-Active Multi-Homing? (Choose two)

Accepted Answer

All-active multi-homing allows multiple PEs attached to the same Ethernet segment to forward traffic simultaneously.. All-active multi-homing allows multiple PEs connected to the same Ethernet segment to actively forward traffic simultaneously and load-balance unicast traffic using aliasing, unlike single-active where only the DF forwards traffic.

Answer

All-active multi-homing restricts host MAC learning to only one PE at a time.

Answer

In all-active mode, only the Designated Forwarder handles unicast traffic from the core.

Answer

All-active multi-homing requires Spanning Tree Protocol to block redundant links.

Question 12

You are deploying an EVPN-VXLAN fabric on Juniper MX Series routers. A tenant has two VLANs, VLAN 100 and VLAN 200, that must be stretched across the fabric. You configure a single EVPN instance with a VLAN-aware bundle service and assign both VLANs to it. After committing the configuration, you notice that MAC addresses learned in VLAN 100 are being installed in the MAC table for VLAN 200 on remote PEs. Which EVPN route type is used to advertise the VLAN membership and ensure proper VLAN-based forwarding in this scenario?

Accepted Answer

Type-1 Ethernet Auto-Discovery route. In a VLAN-aware bundle service, the EVPN instance can carry multiple VLANs, and the mapping between VLANs and the EVPN instance must be signaled. Type-1 Ethernet Auto-Discovery routes include a VLAN ID field that can specify a VLAN or a bundle of VLANs, allowing remote PEs to correctly associate MAC addresses with their originating VLAN. Without this, MAC addresses from one VLAN may be incorrectly installed in another VLAN's table, causing forwarding issues.

Answer

Type-4 Ethernet Segment route

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Type-3 Inclusive Multicast Ethernet Tag route

Answer

Type-2 MAC/IP Advertisement route

Question 13

You are configuring an EVPN-VXLAN fabric on Juniper switches using an Ethernet VPN (EVPN) instance with a VLAN-based service. A host connected to a leaf switch needs to communicate with a host in a different VLAN on a remote leaf. Which EVPN route type is used to advertise the IP-to-MAC binding for the local host's gateway, enabling inter-subnet routing?

Accepted Answer

Type 2 route (MAC/IP Advertisement route). Type 2 routes advertise MAC and IP bindings. When a host sends traffic to a remote subnet, the local leaf must route it to the gateway. By advertising the gateway's MAC and IP as a Type 2 route, remote leaves learn the binding and can forward traffic to the correct gateway. Type 3 and Type 4 routes serve different purposes, and Type 5 routes are for IP prefixes, not host bindings.

Answer

Type 3 route (Inclusive Multicast Ethernet Tag route)

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Type 4 route (Ethernet Segment route)

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Type 5 route (IP Prefix route)

Question 14

You are configuring an EVPN-VXLAN fabric with a distributed gateway model. You want to enable inter-subnet routing while ensuring that return traffic from a remote subnet is routed optimally without tromboning through a centralized gateway. Which feature should you configure on the PE routers?

Accepted Answer

EVPN Type 5 routes for IP prefix advertisement. EVPN Type 5 routes advertise IP prefixes, enabling distributed inter-subnet routing where each PE can route traffic directly to the destination PE without tromboning through a central gateway. Type 2 routes are for host MAC/IP bindings, centralized gateway models introduce tromboning, and IGP only provides underlay reachability. Thus, Type 5 routes are the correct choice for optimal inter-subnet routing in a distributed gateway model.

Answer

EVPN Type 2 routes with MAC and IP binding

Answer

Centralized gateway with anycast IP

Answer

IGP routing with OSPF or IS-IS

Question 15

You are deploying an EVPN-VXLAN fabric and need to ensure that the underlay network provides reachability between VTEPs. Which routing protocol is commonly used for the underlay in a Juniper EVPN-VXLAN deployment?

Accepted Answer

OSPF. OSPF is a common underlay routing protocol in EVPN-VXLAN fabrics because it provides dynamic VTEP reachability with fast convergence and scalability. BGP is used for the overlay, RIP is legacy and unsuitable, and static routes do not scale. Thus, OSPF is the correct choice for underlay routing.

Answer

Static routes

Answer

BGP

Answer

RIP

Question 16

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?

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 17

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 18

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 19

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 20

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