JN0-650 Juniper Enterprise Routing and Switching - Professional (JNCIP-ENT) Free Practice Exam Questions (2026 Updated)

The exhibit shows the Class of Service (CoS) transmit queue information for interface ge-0/0/11. To determine the correct behavior, we must analyze the bandwidth allocations and the queue limit settings:

Bandwidth Calculation (Option A): In Junos OS, when multiple queues are assigned specific percentages of bandwidth, the "remainder" (represented by 'r') is the total interface bandwidth minus the sum of the explicitly configured percentages.

Bandwidth assigned to Queue 1 (EF) = 10%.

Bandwidth assigned to Queue 2 (AF) = 10%.

Bandwidth assigned to Queue 3 (NC) = 4%.

Total explicitly assigned = $10\% + 10\% + 4\% = 24\%$.

Remainder for Queue 0 (Best Effort) = $100\% - 24\% = 76\%$.

"Limit: exact" Behavior (Option B): The exhibit shows that Queue 2 (assured-forwarding) has a Limit set to exact.

By default, a queue in Junos can consume more than its allocated bandwidth if other queues are idle.

However, when the exact keyword is applied to the transmit-rate (transmission rate), the queue is strictly rate-limited to its configured percentage.

This means that traffic in Queue 2 will be capped at 10% of the interface bandwidth regardless of whether the network is congested or not. If the traffic exceeds 10%, the excess will be dropped or buffered to match the exact rate.

Option C is incorrect because 100% of the bandwidth is not reserved for a single queue; it is distributed across four queues.

Option D is less accurate than B because it implies the drop behavior only occurs during congestion. The exact parameter enforces the limit even when the rest of the interface is completely idle.

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.

OSPFv2 (IPv4) and OSPFv3 (IPv6) share many fundamental concepts, such as the SPF algorithm and the use of areas, but they have distinct differences in how they handle prefix information and LSA headers in Junos OS.

Backbone Requirement (Option C): Both OSPFv2 and OSPFv3 utilize a hierarchical structure. In both versions, all areas must connect to a central Area 0 (the backbone) to allow for inter-area routing. If an area is not physically connected to Area 0, a virtual link must be established.

Flooding Scope (Option D): One of the significant architectural changes in OSPFv3 is the inclusion of the flooding scope directly into the LSA header. In OSPFv3, the LS Type field is expanded to 16 bits, where the top three bits define the flooding scope (e.g., Link-local, Area, or AS scope). This allows routers to understand how far an LSA should be propagated without needing to understand the specific LSA type itself.

LSA Prefix Information (Option A): This statement is misleading. In OSPFv2, Router and Network LSAs (Type 1 and 2) carry both topology and prefix information. However, a key design goal of OSPFv3 was to separate topology from prefix information. In OSPFv3, Type 1 and 2 LSAs only describe the topology, while prefixes are carried in new LSA types: Intra-Area-Prefix-LSAs (Type 9) and Link-LSAs (Type 8).

Processing (Option B): OSPFv2 is processed "per-subnet" because it forms adjacencies based on IPv4 subnets. OSPFv3 is processed "per-link", meaning it forms adjacencies between interfaces on the same physical link regardless of whether they share a common IPv6 prefix.

The exhibit shows router1 (AS 65001) connected to router2 (AS 65002) via two parallel physical links. The show bgp summary output indicates that sessions are established with two neighbors: 10.10.10.1 and 10.10.20.1. Currently, for the second neighbor (10.10.20.1), there are 0 active routes despite having 4 accepted routes, which indicates that BGP has selected only one "best path" via the first neighbor for forwarding.

BGP Best Path Selection: By default, BGP only selects a single best path for any given destination prefix and installs that one path into the forwarding table. In a topology with parallel links to the same AS, this leads to underutilization of available bandwidth.

Multipath Solution (Option B): To enable active routes from both peers and allow for load-balancing (ECMP) across both links, you must enable the multipath feature.

When the multipath statement is configured under the protocols bgp group ext-peers hierarchy, it tells Junos OS to install multiple equal-cost BGP paths into the routing table and subsequent forwarding table.

Since both neighbors belong to the same peer group (ext-peers) and the same AS (65002), configuring multipath at the group level will apply to both sessions, allowing paths from both neighbors to be marked as "active".

Incorrect Options:

Option A: 172.16.1.1 is the loopback address of router2. The exhibit shows peering is currently done using physical interface addresses (10.10.10.1 and 10.10.20.1), so this address is irrelevant to the current active sessions.

Option C: Configuring the neighbor address alone without the multipath parameter will not change the best-path selection behavior.

Option D: 10.10.20.2 is the local interface IP of router1, not the neighbor's IP. BGP multipath must be configured to point to remote peer paths.

Configuration Example for Junos OS 24.4: To implement this, apply the following command: set protocols bgp group ext-peers multipath

In Junos OS routing policies, the order of evaluation and the impact of terminal actions are critical for predictable control.

Immediate Execution (Option D): When a route-filter contains an explicit action like accept or reject within its block, that action is considered terminal if a match is found.

Evaluation Flow: The policy engine processes terms and conditions from top to bottom. If a prefix matches a route-filter that has an embedded accept action, the policy executes that action immediately and stops further evaluation of that specific term. Consequently, any subsequent then clause in the same term is completely ignored.

Best Practice: To ensure a then clause (which might include modifications like changing a preference or community) is executed, the route-filter should be defined without an internal action, allowing the match to fall through to the term's common then statement.

In an EVPN-VXLAN architecture, the network is divided into two distinct planes: the Underlay and 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 signaling is the standard mechanism for this task.

Protocol Choice (Option D): EVPN uses MP-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 is EBGP (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 B refer 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.

This scenario describes a specific use case where a switch port is shared by multiple devices (e.g., via a downstream unmanaged switch), and you want to simplify the authentication process.

Single Supplicant Mode (Option A): In this mode, the switch requires only the first device that connects to the port to successfully authenticate via 802.1X. Once that first device is authorized, the switch "opens" the port for all traffic. This means all subsequent devices attached to that same downstream switch are permitted to access the network without undergoing their own authentication.

Other Modes:

Single-secure supplicant (C): Only allows the first authenticated device; all others are blocked.

Multiple supplicant (D): Requires every device to authenticate individually.

MAC RADIUS (B): This is an authentication method, not a port-control mode.

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 exhibit displays the default-switch.evpn.0 routing table, which is used on Juniper leaf devices to store EVPN Type 2 (MAC/IP) routes.

Route Distinguisher (Option C): In EVPN, the Route Distinguisher (RD) is an 8-byte prefix added to a route to make it unique within the BGP control plane. The RD format in the exhibit is :.

For example, the prefix 2:192.168.100.1:1::5010::... indicates an EVPN Type 2 route (2:) where 192.168.100.1:1 is the Route Distinguisher.

This RD identifies the specific routing instance on the originating VTEP that advertised the MAC/IP address.

Option A is incorrect: The RD 192.168.100.2:1 does not necessarily mean the host device has that IP; it means the originating switch has that router ID/IP used for its RD.

Option B is incorrect: While the RD often incorporates the router ID, the RD itself is the full string (e.g., 192.168.100.1:1), which is distinct from the raw Router ID used in the BGP summary.

Option D is incorrect: Looking at the entries for 10.1.1.1 and 10.1.2.3, they are associated with different identifiers in the RD strings (5010 and 5020 respectively), which typically map to different VNIs or bridge domains.

To interoperate with Cisco switches running Per-VLAN Spanning Tree Plus (PVST+), Juniper devices must use VLAN Spanning Tree Protocol (VSTP).

PVST+ Compatibility: VSTP is specifically designed to handle the per-VLAN BPDU requirements of Cisco's PVST+. It generates a separate spanning tree instance for each VLAN and uses the same multicast destination MAC address as Cisco devices.

Other Protocols: MSTP (B) is used for grouping VLANs into regions; RSTP (D) is a single-instance protocol (IEEE 802.1w) and is generally incompatible with per-VLAN BPDU requirements without additional configuration.

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 a flexible authentication order. By default, the switch attempts authentication in the order of 802.1X, then MAC RADIUS, and finally Captive 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 an authentication 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 the last method 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 control Layer 2 access on EX Series switches.

In this scenario, router1 (AS 65001) is attempting to establish an External BGP (EBGP) peering with router2 (AS 65002) using their loopback (lo0) interface addresses (192.168.1.1 and 172.16.1.1).

According to the Junos OS 24.4 documentation on BGP peering sessions:

EBGP TTL Default: By default, EBGP packets are sent with a Time-to-Live (TTL) value of 1. This assumes the peer is directly connected on a shared physical subnet.

Loopback Peering Challenge: When peering between loopback addresses, the destination IP is not on the same subnet as the physical ingress interface. Even if the routers are directly connected physically, the router treats the loopback interface as an additional "hop". With a TTL of 1, the BGP packet expires before it can be processed by the peer's routing engine.

The Multihop Solution (Option D): To allow this session to form, you must configure the multihop statement under the BGP neighbor hierarchy. This tells Junos to increase the TTL (the default becomes 64 when multihop is enabled) and allows the session to establish even though the peer's address is not directly connected.

Target Neighbor: The neighbor address specified in the configuration on router1 must be the remote loopback address of router2 (172.16.1.1).

Option A (Multipath) is incorrect because it is used for load balancing across multiple active BGP paths, not for initial session establishment.

Options B and C are incorrect because they reference physical interface addresses (10.10.20.1 or 10.10.10.1) which are not the addresses being used for the loopback-based BGP session.

In standard BGP operations, a router typically selects only one "best path" for a given destination prefix and installs that single path into the forwarding table. To utilize multiple paths for traffic forwarding (load-balancing), specific multipath features must be enabled.

BGP Multipath: This feature allows a router to install multiple equal-cost paths into the routing and forwarding tables. However, by default, BGP multipath requires that all candidate paths have the same neighboring Autonomous System (AS).

Multipath Multiple-AS (Option B): In the exhibit, R1 is receiving routes from ISP A (AS 65501) and ISP B (AS 65502). Since these are two different neighboring ASs, the standard multipath feature is not sufficient. You must use the multipath multiple-as statement under the BGP group or neighbor hierarchy. This tells Junos to consider paths as equal even if they originate from different neighboring ASs, provided all other BGP path selection attributes (Local Preference, AS Path length, Origin, MED, etc.) are identical.

Why other options are incorrect: * Option A (multihop) is used for peering with routers that are not directly connected.

Option C (prefix limit) is a security and stability feature to limit the number of prefixes received from a neighbor.

Option D (damping) is used to penalize unstable, "flapping" routes to prevent constant routing table churn.

Configuration Example for Junos OS 24.4: To implement this on R1, you would use the following configuration:

set protocols bgp group multipath multiple-as

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 to Single, and the Number of connected supplicants is 2. This indicates that the 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 why Option C is 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 to only one MAC 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

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.

In Junos OS 24.4, the no-loss forwarding class is used for traffic that requires lossless delivery, such as iSCSI or FCoE, typically in a Data Center Bridging (DCB) environment.

Priority-Based Flow Control (Option C): To guarantee "no-loss" behavior, the switch must support and use Priority-based Flow Control (PFC). PFC allows the switch to send "pause" frames for a specific priority (forwarding class) to prevent buffer overflow and packet drops without affecting other traffic on the same link.

Forwarding Class Sets (Option B): In enhanced Layer 2 software (ELS) versions used by modern QFX and EX series switches, lossless traffic must be managed within forwarding class sets (also known as priority groups). This grouping is necessary to apply specific DCB properties, such as PFC and specific bandwidth guarantees, to the lossless traffic class.

Why A and D are incorrect: Default scheduler maps and default drop profiles do not provide the specialized buffer management or lossless signaling required for this class. Lossless traffic specifically requires the suppression of tail drops rather than standard drop profiles.

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 a maximum threshold for 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 or tear down the BGP session entirely (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.

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 a Community VLAN (RND) to reach members on a different switch, the Community VLAN must have its own 802.1Q 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 A is incorrect because the community VLAN must have a different tag than the parent (Primary) VLAN to maintain the internal PVLAN logic. Option C is incorrect because stripping tags would lead to the traffic being merged into the native VLAN or dropped. Option D is 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).