Free and Premium Juniper JN0-650 Dumps Questions Answers

The exhibit illustrates an Autonomous System (AS 65512) receiving the same prefix ($203.0.113.0/24$) from two different neighbors, ISP A and ISP B. To influence outbound traffic from AS 65512 so that ISP A is preferred, you must manipulate the BGP Local Preference attribute.BGP Path Selection and Local Preference: Local preference is the first attribute evaluated by BGP after checking if the next hop is reachable. A higher local preference value is always preferred over a lower one. The default value in Junos OS is 100.Applying the Preference (Option B): By applying an import policy on router R1 to set a local preference higher than 100 (e.g., 200) for routes from ISP A, R1, R2, and R3 will all prefer the path through R1 to reach ISP A.Applying the Preference (Option C): Alternatively, you can achieve the same result by applying an import policy on R2 to set a local preference lower than 100 (e.g., 50) for routes from ISP B. Since the routes from R1 remain at the default of 100, the path through ISP A (100) will be preferred over ISP B (50).Why A and D are incorrect: Setting a lower preference for ISP A (Option A) or a higher preference for ISP B (Option D) would result in ISP B being preferred for outbound traffic, which is the opposite of the requirement.

Private VLANs (PVLANs) allow for granular port isolation within a single broadcast domain. When extending a PVLAN across multiple switches (S1 to S2), the secondary VLANs (Community or Isolated) must be preserved across the trunk links.

802.1Q Tagging (Option B):For traffic from aCommunity VLAN (RND)to reach members on a different switch, the Community VLAN must have its own802.1Q VLAN tag (VLAN ID)associated with it. When a frame from a community port on S1 traverses the trunk to S2, it is tagged with this specific secondary VLAN ID. S2 receives the tagged frame, identifies it as belonging to the RND community, and forwards it to the appropriate community or promiscuous ports.

Why it fails without a tag:If the RND community is only defined locally on S1 without a global VLAN ID, the trunk port will not know how to distinguish that traffic from the Primary VLAN or other communities.

Incorrect Options:Option Ais incorrect because the community VLANmusthave a different tag than the parent (Primary) VLAN to maintain the internal PVLAN logic.Option Cis incorrect because stripping tags would lead to the traffic being merged into the native VLAN or dropped.Option Dis incorrect because RND is a community VLAN; changing it to an isolated VLAN would change its behavior (preventing communication between members of that same group).

VSTP (VLAN Spanning Tree Protocol) is Juniper's implementation that provides a separate spanning tree instance for each VLAN, ensuring compatibility with Cisco's PVST+. However, it has significant scaling limitations:

Instance Limits:On many Juniper EX and QFX series switches, VSTP is restricted to a maximum of253 or 510 VLAN instancesdepending on the software version (ELS vs. non-ELS). In your scenario, having450 VLANsexceeds the standard 253-instance limit found on many platforms.

The Solution (Option B):When the number of VLANs exceeds the VSTP capacity, the recommended best practice is toenable RSTP(Rapid Spanning Tree Protocol). Unlike VSTP, RSTP runs asingle spanning tree instancefor the entire switch, regardless of how many VLANs are configured. This ensures that all 450 VLANs are protected from loops without hitting the hardware's instance-count limit.

Other Options:Option A(force-version) only affects the BPDU format for compatibility but doesn't solve the instance limit.Option CandOption Dare parameter tuning actions that do not address the architectural limitation of the number of running instances.

Junos OS 24.4 provides several server-failover options for 802.1X authentication to maintain network availability when the RADIUS server is unreachable.

Fallback Behavior (Option D):Theuse-cachefallback action allows the switch to consult its local cache of previously authenticated MAC addresses.

If a device was already authorized and its information is in the cache, the switch willcontinue to permit accessbased on those cached credentials.

However, if a new device (not in the cache) attempts to connect while the server is down, the switch cannot verify its credentials and willdeny the access attempt. This matches the specific requirement to permit authorized devices while denying new ones.

Other Fallback Options:

permit (Option C):This would allowalldevices (even new ones) to access the network, typically in a restricted "guest" or "bypass" VLAN.

deny (Option A):This would drop all traffic from all devices on the port if the server is unreachable.

vlan-name (Option B):This moves authenticated or unauthenticated users into a specific fallback VLAN.

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.

When 802.1X server fail fallback is enabled with the vlan-name feature, the switch provides a specific survival mechanism for both existing and new sessions when the RADIUS server becomes unreachable.

Existing Clients (Statement B): Clients that have already successfully authenticated are unaffected by the server's unavailability in the short term. They maintain their current network access until their specific re-authentication timer expires. Only then will the switch attempt to contact the server again and trigger the fallback action if the server remains down.

New Clients (Statement D): For any new device attempting to connect while the RADIUS server is down, the switch cannot perform a standard authentication. Under the vlan-name fallback configuration, these new clients are automatically placed into the specified fallback VLAN and granted access based on the local policy defined for that VLAN.

Why others are incorrect: Statement A is incorrect because disconnecting active users would cause unnecessary service disruption. Statement C is incorrect because new clients cannot "request" a VLAN during the 802.1X handshake; the switch assigns it based on the fallback configuration.

The IETF standards for EVPN-VXLAN define the scalability and forwarding behavior of the architecture.

VXLAN Scale (Statement B):The Virtual Network Identifier (VNI) is a24-bit fieldin the VXLAN header. This allows for up to $2^{24}$ unique identifiers, which translates to approximately16 milliondistinct VXLAN broadcast domains (segments) within a single fabric. *Forwarding Behavior (Statement D):VXLAN is a MAC-in-UDP encapsulation technology. When a Layer 2 frame enters the tunnel at a VTEP, theoriginal Layer 2 frame(including the original source and destination MAC addresses) is encapsulated into a UDP/IP packet and transported across the IP underlay. When it reaches the egress VTEP, the header is removed and theLayer 2 frame is forwarded unchangedto the destination host.

Why others are incorrect:Statement A is incorrect because EVPN itself can technically support more than 16 million domains, but the data plane (VXLAN) is the limiting factor in this specific deployment scenario. Statement C is incorrect because VXLAN encapsulates Layer 2 frames, not just "IP packets," and it treats the entire frame as a payload.

In a three-stage EVPN-VXLAN fabric (Spine-Leaf architecture) where leaf devices perform the gateway services (Edge-Routed Bridging or ERB):

VTEP Functionality (Option B):Leaf devices act asVXLAN Tunnel End Points (VTEPs). They are responsible for encapsulating Ethernet frames from locally connected hosts into VXLAN packets for transport across the IP fabric and de-encapsulating incoming VXLAN packets.

Fabric Support (Option C):In a standard Juniper IP fabric design, both theleaf and spine devicesare typically expected to support VXLAN and EVPN capabilities. While spines in an ERB design might only perform IP forwarding in the underlay, they often participate in the BGP control plane (as Route Reflectors) or provide the ability to transition to Centrally-Routed Bridging (CRB) where spines would act as gateways.

Incorrect Options:Option Ais incorrect because the entire fabric infrastructure must be "VXLAN aware" in terms of MTU settings and routing capability to support the overlay.Option Dis incorrect because in an ERB design, the spine devices are high-speed transit nodes and do not terminate VXLAN tunnels; only the edge (leaf) devices act as VTEPs.

The exhibit shows the output of the show poe interface command on a Juniper switch.

VTEP Power Capabilities (Statement D):The exhibit shows the Pair/Mode as 2P/AT, which refers to theIEEE 802.3at(PoE+) standard. Under this standard, a switch can supply up to30 Wof power per port to attached devices (PDs). *Dynamic Learning (Statement C):Looking at the Max power column for port ge-0/0/0, it shows 19.5W(L). The(L)indicator signifies that the power has beendynamically learned(negotiated) via LLDP or hardware classification, rather than being statically configured by an administrator. Additionally, it has identified the device asClass 4, which is a standard dynamic classification for PoE+ devices.

Why others are incorrect:Statement A (60 W) refers to the 802.3bt (PoE++) standard, which is not indicated here. Statement B is incorrect because the "(L)" confirms the configuration is not static.

In Junos OS 24.4, Captive Portal is used as a web-based authentication method for Layer 2 network access control, often in environments where 802.1X is not feasible for all users.

Fallback Mechanism (Option D):On EX Series switches, Juniper supports aflexible authentication order. By default, the switch attempts authentication in the order of802.1X, thenMAC RADIUS, and finallyCaptive Portal. If a client fails both 802.1X and MAC RADIUS, the switch can fall back to Captive Portal to redirect the user to a login page.

MAC Allowlist (Option B):Captive Portal relies on intercepting HTTP/HTTPS traffic to redirect users. However, "headless" devices like printers or cameras lack web browsers and cannot interact with the portal. To accommodate these, Junos allows administrators to configure anauthentication allowlist(or whitelist), which identifies these devices by their MAC addresses and permits them to bypass the portal entirely.

Precedence (Option A):This is incorrect because Captive Portal is generally thelastmethod in the default sequence, not the first.

Layer 2 Participation (Option C):While Captive Portal requires a Layer 3 interface (RVI/IRB) for the redirection process, it is explicitly used to controlLayer 2 accesson EX Series switches.

When a peer incorrectly floods your router with an excessive number of routes, it can exhaust system resources and crash the routing engine.

Prefix-Limit (Option B):The prefix-limit (or accepted-prefix-limit) parameter is the primary defense against such "route leaks".

You can set amaximum thresholdfor the number of prefixes allowed from a specific BGP neighbor or group.

When the limit is reached, Junos can be configured to either just log a warning ortear down the BGP sessionentirely (using the teardown keyword) to protect the router.

This prevents the "hundreds of thousand routes" from ever being fully processed or installed into the main routing table.

Damping (Option A):Damping is used to suppress unstable, "flapping" routes, but it does not limit the total volume of stable routes received.

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.

For maintenance scenarios where a router must remain operational but should not be used as a transit path for OSPF traffic, Junos OS uses theoverloadfunctionality.

OSPF Overload (Option B):When you enable overload under protocols ospf, the router advertises its own Link-State Advertisements (LSAs) with amaximum metric (65535)for all of its transit links.

Traffic Diversion:Because OSPF uses the Shortest Path First (SPF) algorithm to find the lowest-cost path, other routers in the network will see the overloaded router as an extremely high-cost path. They will calculate alternate routes, effectivelymoving transit traffic off the routerwhile still allowing management traffic directedtothe router's own interfaces.

Timeout Options:You can configure this to be permanent or set a timeout so that the router automatically resumes normal metric advertisements after a set period.

In Junos OS Class of Service (CoS),schedulersare the components that define how traffic in a specific queue is treated before it is transmitted out of an interface.

Queue Priority (Statement C):A scheduler identifies thepriorityof the queue (e.g., low, medium-low, medium-high, or high). This determines the order in which the hardware handles traffic from different queues.

Buffer Size (Statement D):A scheduler defines thebuffer size(amount of memory) allocated to a queue, which can be specified as a percentage, a temporal value (in microseconds), or the remainder of available buffer space. This helps manage bursts of traffic and prevent tail drops.

Other Components:Rate-limiting (Statement A) is typically handled bypolicersor interface-level shaping, while code translation (Statement B) is the role ofrewrite rules.

The exhibit shows a BGP routing process where anImport Policyis being applied to routes received in theRIB-IN. Specifically, Policy 1 states:"Reject 0.0.0.0/0 from AS 64512."

In Junos OS, when a routing policy rejects a route, that route is not placed in the main routing table (inet.0) for active use. Instead, it becomes ahidden route. To verify that a specific peer is actually sending a route that is subsequently being rejected by your policy, you must use specific diagnostic commands:

Understanding "Hidden" Routes:When a BGP route is received but fails to meet policy requirements (or has an unreachable next-hop), Junos keeps it in the BGP RIB-IN but marks it as "hidden." It will not appear in a standard show route command.

Command Logic (Option D):The command show route receive-protocol bgp hidden allows an administrator to view all routes received from a specific neighbor, including those that wererejected by import policies.

show route receive-protocol bgp : Shows only the routes that passed the import policy and were accepted into the table. Since the 0.0.0.0/0 route from AS 64512 is explicitly rejected in the exhibit, it would not show up here.

Adding the hidden keyword is the essential step to see the rejected default route and verify that AS 64512 is indeed sending it before the policy drops it.

Other Options:

Option Ais incorrect because it only shows accepted routes.

Option B and Care used to filter the existing active routing table based on gateway or next-hop attributes, but they cannot show routes that have been rejected and excluded from that table.

In an EVPN-VXLAN architecture, the interaction between the control plane (EVPN) and the data plane (VXLAN) is defined by specific functional components:

VTEP (VXLAN Tunnel End Point):These are the entities responsible for theencapsulation and de-encapsulationof Layer 2 Ethernet frames into Layer 3 UDP/IP packets. A VTEP can be a physical switch (like a QFX or EX series) or a software-based entity. When traffic enters the fabric, the ingress VTEP wraps it in a VXLAN header; the egress VTEP removes this header before delivering it to the destination host. (Option B)

VNI (Virtual Network Identifier):The VNI is a 24-bit field in the VXLAN header that allows for up to 16 million unique identifiers. It is used toidentify specific broadcast domains(or VLANs) within the overlay network. Each VNI effectively represents a virtualized Layer 2 segment that is stretched across the Layer 3 underlay. (Option D)

Incorrect statements:Option Ais incorrect because VNIs are identifiers, not the "engine" that performs encapsulation—that is the VTEP's job.Option Cis incorrect because VTEPs identify the endpoints of a tunnel, not the individual broadcast domains themselves.

In OSPF, the election of aDesignated Router (DR)and aBackup Designated Router (BDR)is mandatory on broadcast and non-broadcast multi-access (NBMA) network types to manage link-state database synchronization efficiently.

The exhibit shows that bothdevice1anddevice2have their OSPF interface priority explicitly set to0. According to the Junos OS 24.4 OSPF implementation:

Ineligibility (Priority 0):A router with a priority of 0 is strictlyineligibleto be elected as a DR or BDR for that segment.

No Election Possible:When every router on a broadcast segment has a priority of 0, the election process cannot complete because there are no eligible candidates to fill the required roles.

State Behavior (Stuck in 2-Way):In OSPF adjacency formation, the2-Way stateindicates that bidirectional communication has been established (each router has seen itself in the other's Hello packets). However, to progress to theExstartandExchangestates on a multi-access network, routers must first identify a DR and BDR.

Result:Since neither router can become the DR, they both wait indefinitely for a third party (with priority > 0) to take the lead. Consequently, the OSPF adjacency will bestuck in the 2-Way state. Adjacencies only reach theFullstate with the DR and BDR; routers in a "DROther" role remain in 2-Way with each other.

Option A and Dare incorrect because the router ID (IP address) only acts as a tiebreaker if priorities are equal andgreater than 0.Option Bis incorrect because routers cannot reach the Exstart state (where they negotiate master/slave for database exchange) without first having a DR/BDR elected.

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.