Juniper JN0-683 Practice Test - Questions Answers, Page 6

Understanding Oversubscription in a Clos Fabric:

The oversubscription ratio in a Clos IP fabric measures the ratio of the amount of edge (leaf) bandwidth to the core (spine) bandwidth. An oversubscription ratio of 3:1 means that there is three times more edge bandwidth compared to core bandwidth.

Impact of Adding/Removing Spine Devices:

Option C: If you remove spine devices, the total available core bandwidth decreases, while the edge bandwidth remains the same. This results in an increase in the oversubscription ratio because there is now less core bandwidth to handle the same amount of edge traffic.

Option B: Conversely, if you add spine devices, the total core bandwidth increases. This decreases the oversubscription ratio because more core bandwidth is available to handle the edge traffic.

Conclusion:

Option C: Correct---Removing spine devices increases the oversubscription ratio.

Option B: Correct---Adding spine devices decreases the oversubscription ratio.

Analyzing the Exhibit Output:

The command ping overlay tunnel-type vxlan is used to test the VXLAN tunnel between two VTEPs (VXLAN Tunnel Endpoints). The output shows a warning about missing hash parameters, but more importantly, it displays the result: End-System Not Present.

Understanding the Response:

The message End-System Not Present indicates that the remote VTEP (192.168.2.20) did not find the MAC address 00:00:5E:00:53:CC in its forwarding table. This typically means that the MAC address is unknown to the remote VTEP, and as a result, it could not forward the packet to the intended destination.

Conclusion:

Option B: Correct---The MAC address is unknown and is not in the forwarding table of the remote VTEP, which is why the system reports that the 'End-System' is not present.

MAC Move Limiting:

MAC move limiting is a security feature used in network switches to detect and mitigate rapid changes in MAC address locations, which could indicate a network issue or an attack such as MAC flapping or spoofing.

When a MAC address is learned on a different interface than it was previously learned, the switch can take various actions to prevent potential issues.

Available Actions:

A . drop: This action drops packets from the MAC address if it violates the move limit, effectively blocking communication from the offending MAC address.

D . log: This action logs the MAC move event without disrupting traffic, allowing network administrators to monitor and investigate the event.

E . shutdown: This action shuts down the interface on which the MAC address violation occurred, effectively stopping all traffic on that interface to prevent further issues.

Other Actions (Not Correct):

B . filter: Filtering is not typically associated with MAC move limiting; it generally refers to applying ACLs or other mechanisms to filter traffic.

C . enable: This is not an action related to MAC move limiting, as it does not represent a specific reaction to a MAC move event.

Data Center

Reference:

MAC move limiting is crucial for maintaining network stability and security, particularly in environments with dynamic or large-scale Layer 2 networks where MAC addresses might frequently change locations.

Understanding BGP Configuration in the Exhibit:

The exhibit shows a BGP configuration on spine1 with a group named underlay, configured to peer with directly connected interfaces of other devices in the network.

Multipath multiple-as: This statement allows the router to install multiple paths in the routing table for routes learned from different ASes, facilitating load balancing.

Key Statements:

A . The multihop statement is not required to establish the underlay BGP sessions: In this case, the BGP peers are directly connected (as indicated by their neighbor IP addresses), so the multihop statement is unnecessary. Multihop is typically used when BGP peers are not directly connected and packets need to traverse multiple hops.

D . Load balancing for the underlay is configured correctly: The multipath { multiple-as; } statement in the configuration enables load balancing across multiple paths from different autonomous systems, which is appropriate for underlay networks in data center fabrics.

Incorrect Statements:

C . The multihop statement is required to establish the underlay BGP sessions: This is incorrect because the peers are directly connected, making the multihop statement unnecessary.

B . Load balancing for the underlay is not configured correctly: This is incorrect because the configuration includes the necessary multipath settings for load balancing.

Data Center

Reference:

BGP configurations in EVPN-VXLAN underlay networks are crucial for ensuring redundancy, load balancing, and efficient route propagation across the data center fabric.

Telemetry Methods in Junos:

Telemetry is used to collect and report data from network devices. For high-frequency statistics reporting, such as every five seconds, you need a telemetry method that supports this level of granularity and real-time monitoring.

Junos Native Sensors:

Option C: Native Sensors in Junos provide detailed, high-frequency telemetry data, including TX and RX traffic statistics for interfaces. They are designed to offer real-time monitoring with customizable sampling intervals, making them ideal for the five-second reporting requirement.

Conclusion:

Option C: Correct---Native Sensors in Junos are capable of providing the required high-frequency telemetry data every five seconds.

VXLAN Control Planes:

VXLAN (Virtual Extensible LAN) uses different control planes to handle MAC learning and traffic forwarding. The control planes include multicast and EVPN (Ethernet VPN).

Multicast and EVPN Comparison:

Option B: Both multicast and EVPN can be used for MAC learning in a VXLAN environment. Multicast is a more traditional approach, while EVPN is more advanced and supports distributed MAC learning.

Option D: EVPN offers benefits such as fast convergence and rapid updates, making it more efficient and scalable for modern data center environments.

Option E: Multicast does not require as many resources because it relies on traditional Layer 3 multicast mechanisms to distribute broadcast, unknown unicast, and multicast (BUM) traffic. However, it can be less flexible and less scalable compared to EVPN.

Conclusion:

Option B: Correct---Both control planes facilitate MAC learning.

Option D: Correct---EVPN provides fast convergence and updates.

Option E: Correct---Multicast is resource-efficient but less flexible.

Understanding Lossless Ethernet and Congestion Management:

Lossless Ethernet is crucial for AI and ML workloads, where packet loss can significantly degrade performance. To implement lossless Ethernet, congestion management protocols like ECN (Explicit Congestion Notification) are used.

Role of ECN in Congestion Management:

Option A: In an IP fabric that supports lossless Ethernet, when a switch experiences congestion, it can mark packets using ECN. This marking notifies the source device of the congestion, allowing the source to reduce its transmission rate, thereby preventing packet loss.

Conclusion:

Option A: Correct---The switch experiencing congestion notifies the source device via ECN marking.

Understanding Network Architectures:

ERB (Edge Routed Bridging) architecture involves routing at the network's edge (leaf nodes), while traffic between leaf nodes is switched. This is commonly used in VXLAN-EVPN setups.

Analysis of the Exhibit:

The exhibit shows configurations related to routing instances, VXLAN, and VLANs, with VNIs being used for each VLAN. This setup is characteristic of an ERB architecture where each leaf device handles Layer 3 routing for its connected devices.

Conclusion:

Option B: Correct---The configuration shown corresponds to an ERB architecture where routing occurs at the network's edge (leaf devices).

Review of the Exhibit:

The exhibit shows the switch configuration for Leaf-1 and Leaf-2. The configurations include route distinguishers, VRF targets, and service IDs, all of which are crucial for ensuring proper operation in an EVPN-VXLAN environment.

Service-ID Consistency:

The service ID must be consistent across all participating leaf devices in the same EVPN instance to ensure that they are part of the same VXLAN overlay network.

VRF Target Consistency:

The vrf-target parameter must also be consistent across devices to ensure that VRFs (Virtual Routing and Forwarding instances) are correctly imported and exported between leaf nodes.

Conclusion:

Option B: Correct---Setting the same service-id on Leaf-2 ensures that it is part of the same VXLAN overlay as Leaf-1.

Option D: Correct---The vrf-target on Leaf-2 should match Leaf-1 to ensure consistent routing policies and proper route exchange.