JNCIP-ENT EVPN — 10 Questions

Question 1

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?

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

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 2

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?

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

Answer

Route Type 4 (Ethernet Segment Route)

Answer

Route Type 3 (Inclusive Multicast)

Question 3

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

Answer

multicast-snooping

Answer

vtep-source-interface lo0.0

Question 4

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 5

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 6

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

Answer

gre0

Answer

fxp0

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

Answer

Route Type 1

Question 8

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

Answer

show bgp summary

Answer

show evpn database

Question 9

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 10

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