Most Recent Juniper JN0-650 Exam Dumps

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

In an EVPN-VXLAN environment using ESI-LAG (Ethernet Segment Identifier Link Aggregation), the Core Isolation feature is a safety mechanism designed to prevent traffic blackholing. When a leaf switch (acting as a VTEP) loses its BGP peering or its link to the IP fabric core, it assumes it is 'isolated' from the rest of the network. To protect the network, the switch automatically shuts down its local member links of any multi-homed ESI-LAG to force traffic to the peer switch that still has core connectivity.

However, during a migration or in specific transitional topologies where the core might be temporarily unreachable or not yet fully established, this feature can cause the leaf switches to shut down all downstream IDF (Intermediate Distribution Frame) connections, leading to a total loss of connectivity.

The Solution (Option C): By enabling the no-core-isolation statement under the [edit protocols evpn] hierarchy, you instruct the switch to disable this automatic shutdown behavior. This ensures that even if the BGP session or core links are not yet stable during the migration process, the ESI-LAG interfaces remain Up, allowing the IDFs to maintain connectivity to their local default gateways or other local resources.

Why others are incorrect: Enabling EVPN-VXLAN before migration (Option A) does not address the isolation logic. Removing MC-LAG/Virtual Chassis links prematurely (Option B) would cause an immediate outage. The network-isolation-profile (Option D) is typically used for different loop prevention scenarios and does not override the specific core-isolation check that affects multi-homed ESIs.

In Junos OS, the figure-of-merit is an internal numerical value used by the BGP Route Damping mechanism to quantify the stability of a specific BGP route. When a route 'flaps' (becomes unstable), the Junos OS increases this value by assigning a specific penalty based on the type of event that occurred:

The route is withdrawn (Option A): When a BGP neighbor sends a withdrawal message for a prefix, Junos assigns a significant penalty---typically 1,000 by default---to the route's figure-of-merit.

The route is readvertised (Option C): When a previously withdrawn route is announced again by the neighbor, the Junos OS adds another penalty to the figure-of-merit value to track the continued instability.

The route's path attributes changed (Option E): If a route remains reachable but its BGP attributes (such as the AS Path or Community) change, it is considered a flap. Junos assigns a smaller penalty---typically 500 by default---for this attribute change.

As the figure-of-merit accumulates and exceeds a predefined suppress threshold, the route is suppressed and no longer used for forwarding. Over time, the value decreases according to a configured half-life until it falls below a reuse threshold, at which point the route becomes active again. Factors like local preference or the origin (IBGP/EBGP) do not trigger these internal penalty increments for the figure-of-merit.

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 <IP-Address>:<Identifier>.

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.

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.