In an EVPN-VXLAN architecture, the network is divided into two distinct planes: theUnderlayand the Overlay.
* Underlay (IP Fabric):The underlay's only job is to provide IP reachability between the loopback addresses of all VTEPs (Virtual Tunnel Endpoints). This is typically achieved using OSPF, IS-IS, or EBGP.
* Overlay (EVPN Control Plane):The overlay is responsible for carrying Layer 2 MAC and Layer 3 IP reachability information between switches.EVPN signalingis the standard mechanism for this task.
* Protocol Choice (Option D):EVPN usesMP-BGP (Multiprotocol BGP)as its control plane protocol.
On Juniper EX Series and QFX Series switches, the most scalable and recommended design for the overlay isEBGP(External BGP).
* In a 3-stage or 5-stage Clos architecture, EBGP is used in the overlay to exchange EVPN routes (Route Types 1-5) between Leaf and Spine switches.
* EBGP simplifies configuration by avoiding the need for Route Reflectors (required for IBGP) and provides better control over route propagation through BGP community and policy management.
Incorrect Options:
* Options A and Brefer to the underlay protocols. While they provide the path for the VXLAN tunnels, they do not handle the EVPN signaling itself.
* Option C(MPLS) is a different transport technology. While EVPN can run over MPLS (EVPN-MPLS), campus designs on EX series devices specifically use VXLAN as the data plane, making EBGP the standard signaling protocol for the EVPN-VXLAN overlay.

The exhibit shows an OSPF network where Area 1 is configured as a Not-So-Stubby Area (NSSA). R5 is an Autonomous System Boundary Router (ASBR) injecting an External Route (203.0.113.0/24) into this area.
NSSA ASBR Behavior (Option D): Within an OSPF NSSA, external routes cannot be advertised as standard Type 5 LSAs because stubby areas do not support them. Instead, the ASBR (R5) advertises the external prefix using a Type 7 LSA (NSSA External LSA). This LSA is flooded throughout Area 1.
ABR Translation Behavior (Option C): When the Type 7 LSA reaches the Area Border Router (R1), the ABR is responsible for translating it into a Type 5 LSA (AS External LSA). This allows the external route to be propagated into the backbone (Area 0) and subsequently to the rest of the OSPF domain.
Incorrect Statements (A & B): Option A is incorrect because Type 7 LSAs are local to the NSSA and are never advertised into Area 0. Option B is incorrect because Type 5 LSAs are strictly prohibited within an NSSA.

The exhibit shows the output of the command show route protocol bgp on router R1 for the prefix 172.16.10.1
/32. To determine the correct characteristics of this route, we analyze the specific BGP attributes and next-hop information provided in the routing table entry:
Multipath Parameter (Option B): The routing table shows two distinct paths for the prefix 172.16.10.1/32. The first path has two next hops (192.168.10.1 and 192.168.20.1) and is marked with the plus symbol (+) and the asterisk (*), indicating it is both an active and the best route. The presence of multiple next hops being used simultaneously for a single BGP path is a clear indication that the multipath parameter is enabled in the BGP configuration. In Junos OS, BGP multipath allows the installation of multiple equal-cost BGP paths into the forwarding table to facilitate load balancing.
Available Next Hops (Option C): The output explicitly lists two functional next hops for the active path:
192.168.10.1 via ge-1/0/0.2 and 192.168.20.1 via ge-1/0/1.3. Both show an outgoing interface, confirming that this route has two next hops available for traffic forwarding.
IBGP vs. EBGP (Option A): The BGP routes shown have an AS path of 200 I. This indicates the routes were learned from an external Autonomous System (AS 200). Furthermore, the protocol preference is 170. In Junos OS, the default preference for External BGP (EBGP) is 170, whereas the default preference for Internal BGP (IBGP) is 200. Therefore, this configuration is for EBGP, not IBGP.
Hidden Next Hops (Option D): The summary line at the top of the exhibit mentions that there are "2 hidden" routes in the inet.0 table. However, these hidden routes are not the next hops for the 172.16.10.1/32 prefix. A hidden route is a prefix that was rejected by policy or has an unreachable next hop; it is not a "hidden next hop" belonging to an active route.

In Junos OS, a physical or logical interface is typically associated with a single OSPF area. However, there are specific design requirements-such as migrating an interface from one area to another without downtime or creating specific transit topologies-where an interface needs to exist in two areas simultaneously.
* Multi-area Adjacency (Option B):The secondary command under the OSPF interface hierarchy allows an interface to be part of asecondary areain addition to its primary area.
* Protocol Behavior:When an interface is configured as secondary, the router sends and receives OSPF Hello packets for both the primary and secondary areas on that single link. This allows the router to form adjacencies with neighbors in both areas over the same physical connection.
* Use Case:This is frequently used in hub-and-spoke topologies or during network restructuring to ensure reachability is maintained while changing area boundaries. It effectively allows a "logical" split of the interface at the OSPF protocol level.