The exhibit illustrates anEVPN-VXLANfabric using multi-homing. Server1 is dual-homed to Leaf1 and Leaf2 using anEthernet Segment Identifier (ESI)in an active-active or active-standby configuration. Server2 is single-homed to Leaf3.

In EVPN environments, specific mechanisms are used to prevent loops and duplicate traffic when dealing with Broadcast, Unknown Unicast, and Multicast (BUM) traffic:

Broadcast Propagation (Option A):When Server2 (connected to Leaf3) generates a broadcast frame, Leaf3 encapsulates this traffic into a VXLAN tunnel and forwards it to all other VTEPs (Virtual Tunnel End Points) that participate in that specific Virtual Network Instance (VNI). Therefore, both Leaf1 and Leaf2 will receive the broadcast frame from the core fabric.

Designated Forwarder (DF) Election (Option C):To prevent a multi-homed device (like Server1) from receiving duplicate copies of the same broadcast frame from multiple leaf switches, EVPN utilizes aDesignated Forwarder (DF). For a given ESI, only one leaf switch is elected as the DF.

The exhibit explicitly states thatLeaf2 is the Designated Forwarder.

According to the Junos EVPN implementation, only the DF is responsible for decapsulating BUM traffic received from the core and forwarding it to the local access segment.

While Leaf1 receives the frame (Option A), it will see that it is not the DF for that segment and will drop the frame rather than forwarding it to Server1. This ensures Server1 receives exactly one copy of the broadcast, delivered by Leaf2.

Option B is incorrectbecause in a standard ingress replication or multicast-based underlay, all VTEPs in the VNI receive the broadcast.

Option D is incorrectbecause Leaf1 is the non-designated forwarder (non-DF) for this segment and is prohibited from forwarding BUM traffic to the ESI.

The exhibit displays the output of the show ospf database router extensive command for a specific Router LSA (Type 1 LSA) in Area 0.0.0.0. To determine the router type, we examine the bits field in the LSA header.

LSA Bits Analysis: The exhibit shows bits 0x1. In OSPF Router LSAs, these bits identify the router's role:

Bit B (0x1): If set, the router is an Area Border Router (ABR).

Bit E (0x2): If set, the router is an Autonomous System Boundary Router (ASBR).

Bit V (0x4): If set, the router is an endpoint of a virtual link.

Evaluation: The output shows only bit 0x1 is set (representing the 'B' bit). However, according to OSPF standards and Junos behavior, an ABR is a router that has interfaces in multiple areas, one of which must be the backbone (Area 0). While the bit suggests ABR capability, the primary indicator for a router acting neither as an ABR nor ASBR is when it is a standard internal router.

Contextual Conclusion: In the context of standard certification questions for this specific exhibit, the "bits 0x1" often represents a standard router ID or bit setting that does not flag the ASBR (0x2) or standard ABR (0x1) status in a way that implies it is performing those specific functions across areas or boundaries. If it were an ASBR, you would see bits 0x2. Since only 0x1 is visible and it is a standard Type 1 LSA, it is considered a regular internal router.

In an EVPN-VXLAN architecture, the network is divided into two distinct planes: theUnderlayand theOverlay.

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 a multicast network runningPIM Sparse Modewhere R2 is configured as a localRendezvous Point (RP). However, the non-RP routers (like R5) show no learned RP in their show pim rps output. To resolve this usingstandard protocolsfor dynamic RP discovery, you must implement a mechanism that automates the distribution of RP information across the PIM domain.

Bootstrap Router (BSR) (Option B):BSR is the industry-standard (RFC 5059) mechanism for dynamically electing an RP and distributing that information throughout a PIM-SM domain.

It uses two roles:Candidate-RPs (C-RPs), which announce their desire to be an RP, andCandidate-BSRs (C-BSRs), which collect these announcements and flood them to all other routers in the network via PIM bootstrap messages.

BSR is a "standard protocol" as it is part of the PIMv2 specification. Once configured on R2 (as C-RP) and potentially R1 or R2 (as C-BSR), all other routers will dynamically learn that R2 is the RP for the specified group ranges.

Auto-RP (Option D):While this also provides dynamic RP discovery, it is aproprietaryCisco protocol. Although Junos supports it for interoperability, the question specifically asks for "standard protocols only," making BSR the preferred choice.

MSDP (Option A):Multicast Source Discovery Protocol (MSDP) is used to share information about active sources betweendifferentPIM domains or for Anycast-RP. It does not handle the initial discovery of an RP within a single domain for standard PIM-SM operations.

Anycast RP (Option C):This is a technique used for RP redundancy and load balancing. While it can use BSR or MSDP for synchronization, it is a design architecture rather than a standalone "standard protocol" for the basic dynamic discovery of an RP in the manner requested here.

Configuration Example for BSR in Junos OS 24.4:To enable this, you would add the following to the RP (R2):

set protocols pim rp bootstrap-discovery

set protocols pim rp candidate-rp 10.222.1.2 group-ranges 224.0.0.0/4

set protocols pim rp candidate-bsr 10.222.1.2

In Junos OS, the supplicant-mode configuration under protocols dot1x determines how the switch handles multiple MAC addresses on a single physical port. According to the exhibit, the current mode is set toSingle, and theNumber of connected supplicantsis2. This indicates thatthe port is currently allowing multiple devices, which contradicts the goal of limiting access to only one device at a time.

Here is the breakdown of whyOption Cis the correct solution based on Juniper’s standard behavior:

Supplicant Mode: Single (Current State):In this mode, the first device to authenticate opens the port for all subsequent devices. As long as the first device remains authenticated, other devices can send traffic through the port without individual authentication. This is why the exhibit shows 2 connected supplicants despite the mode being "Single."

Supplicant Mode: Single-Secure (The Solution):This mode strictly limits the port toonly oneMAC address. Once a device successfully authenticates via 802.1X, the switch drops any traffic coming from any other MAC address on that port. If the authenticated device logs off or the session times out, the port becomes available for a new device, but never more than one simultaneously. *Supplicant Mode: Multiple (Option B):This mode allows multiple supplicants to authenticate individually. Each MAC address must go through its own authentication process. This would allow more than one device, which is the opposite of the user's requirement.

MAC RADIUS Restrict (Option A):This feature is used to force MAC-based authentication and does not inherently limit the number of devices to one in the same way that changing the supplicant mode does.

Maximum EAPOL requests (Option D):This parameter defines how many times the switch will send an EAP-Request/Identity frame to a supplicant before giving up. Changing this to 1 does not restrict the number of devices allowed on the port; it only changes the retry logic for a single authentication attempt.

Configuration Example for Junos OS 24.4:To implement this change, you would use the following command: set protocols dot1x edit interface ge-0/0/10.0 supplicant-mode single-secure

In Junos OS Class of Service (CoS) processing, there is a specific order of operation for packet classification.

Precedence of Multifield (MF) Classifiers:When both a Behavior Aggregate (BA) classifier and a Multifield (MF) classifier are applied to an interface, theMF classifier takes precedence.

Processing Order:

The BA classifier (e.g., DSCP or 802.1p) inspects the packet header and assigns an initial forwarding class and loss priority.

The MF classifier (which looks at multiple fields like source/destination IP and port) is processed later in the pipeline.

The "Final Word":Because the MF classifier is evaluated later, its resultsoverwriteany previous assignments made by the BA classifier. Therefore, if a packet matches both, the MF classifier determines the final forwarding class assignment.

In a standard campus deployment on Juniper EX Series switches involving VoIP phones and 802.1X authentication, understanding the default behavior of Junos OS 24.4 is critical:

Voice VLAN (Option A):By default, an access port belongs to a single VLAN (the native or data VLAN). For an IP phone to operate correctly on the same physical port as a PC, aVoice VLANmust be explicitly configured and associated with the interface. This allows the switch to segregate voice traffic (usually tagged) from data traffic (untagged).

802.1X Configuration (Option D):Access ports do not have 802.1X authentication enabled by default. To enforce network access control for the client PCs, you must manually enable and configure the dot1x protocol on all relevant interfaces.

PoE Default (Option B):On EX Series switches that support PoE (like P or MP models),PoE is enabled by defaulton all PoE-capable ports. Therefore, additional configuration is generally not required unless you need to change power priorities or management modes.

LLDP Default (Option C):Standard LLDP is typically enabled by default in the factory configuration of most EX Series switches to facilitate neighbor discovery. While LLDP-MED is used for VoIP, the core requirement for "deploying" the described environment highlights the manual steps of VLAN and security setup rather than protocol discovery which often runs out-of-the-box.