Understanding EBGP in an IP Fabric:

EBGP (External Border Gateway Protocol) is commonly used in IP fabrics to establish peering between routers, such as leaf and spine nodes, without relying on an Interior Gateway Protocol (IGP) like OSPF or IS-IS.

IGP Requirement for EBGP:

Option B: EBGP peering does not require an IGP for adjacency establishment. This is because EBGP peers are typically directly connected, and BGP establishes its own sessions without needing an underlying IGP.

Leaf-to-Spine Peering:

Option C: In a typical IP fabric, each leaf node establishes an EBGP session with every spine node. This ensures full connectivity between leaves and spines, facilitating efficient routing and forwarding within the fabric.

Conclusion:

Option B: Correct---EBGP does not require an IGP for establishing peering sessions.

Option C: Correct---Each leaf node peers with every spine node, which is a standard practice in IP fabrics to ensure connectivity and redundancy.

Understanding Oversubscription Ratio in IP Fabrics:

The oversubscription ratio in an IP fabric typically refers to the ratio of the available bandwidth at the edge of the network (leaves) to the available bandwidth at the core or spine. A 3:1 oversubscription ratio means that for every 3 units of bandwidth at the leaves, there is 1 unit of bandwidth at the spine.

Impact of Adding or Removing Leaf Devices:

Removing Leaf Devices: When you remove leaf devices, the amount of total edge bandwidth decreases while the bandwidth in the spine remains constant. This causes the oversubscription ratio to increase because there is now less total bandwidth to distribute across the same amount of spine bandwidth.

Adding Leaf Devices: Conversely, when you add leaf devices, the total edge bandwidth increases. Since the spine bandwidth remains the same, the oversubscription ratio would remain the same if the additional leaves consume their share of the available bandwidth proportionally.

Conclusion:

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

Option D: Correct---Adding leaf devices typically maintains the oversubscription ratio assuming uniform bandwidth distribution.

Multicast-Signaled VXLAN:

In traditional multicast-signaled VXLAN, VTEPs (VXLAN Tunnel Endpoints) use multicast to flood and learn about remote VTEPs. This method relies on multicast in the underlay network to distribute BUM (Broadcast, Unknown unicast, and Multicast) traffic.

This approach can be resource-intensive due to the need for multicast group management and increased network traffic, especially in large deployments.

EVPN-Signaled VXLAN:

EVPN-signaled VXLAN uses BGP (Border Gateway Protocol) to signal the presence of VTEPs and distribute MAC address information. BGP is used for VTEP autodiscovery and the distribution of endpoint information.

This method is more efficient because it reduces the reliance on multicast, instead using BGP control-plane signaling to handle VTEP discovery and MAC learning, which reduces the overhead on the network and improves scalability.

Correct Statements:

B . An EVPN-signaled VXLAN can perform autodiscovery of VTEPs using BGP: This is correct because EVPN uses BGP for VTEP autodiscovery, making it more efficient and scalable compared to multicast-based methods.

C . An EVPN-signaled VXLAN is less resource-intensive: This is correct because it eliminates the need for multicast flooding in the underlay, instead using BGP for signaling, which is less demanding on network resources.

Incorrect Statements:

A . An EVPN-signaled VXLAN can perform autodiscovery of VTEPs using IS-IS: This is incorrect because EVPN relies on BGP, not IS-IS, for VTEP discovery and signaling.

D . An EVPN-signaled VXLAN features slower and more complete convergence: This is incorrect; EVPN with BGP typically provides faster convergence due to its use of a control plane rather than relying on data plane learning.

Data Center Reference:

EVPN-VXLAN is widely adopted in modern data center designs due to its scalability, efficiency, and reduced resource consumption compared to multicast-based VXLAN solutions. It leverages the strengths of BGP for control-plane-driven operations, resulting in more efficient and scalable networks.

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.

Understanding sFlow Monitoring:

sFlow is a packet sampling technology used to monitor traffic in a network. It sends sampled packet data and interface counters to an sFlow collector, which analyzes the traffic patterns.

Information Included in sFlow Datagram:

Option A: The datagram sent to the sFlow collector includes information about the interface through which the packets entered the agent (the switch or router). This is crucial for understanding where in the network the traffic was captured.

Option D: sFlow datagrams also include the source and destination VLAN for the sampled packets. This allows for detailed analysis of the traffic flow within different VLANs.

Conclusion:

Option A: Correct---The ingress interface is included in the sFlow datagram.

Option D: Correct---The source and destination VLANs are also included, providing context for the sampled traffic.