JNCIP-DC JN0-683 Book

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 toincreasebecause 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.

Interconnecting Data Centers:

The scenario requires interconnecting two data centers with unique IP spaces across an IP backbone. The key point is that bridging is not required, so Layer 3 routing methods must be used.

EVPN Configuration:

Option B:Establishing EVPN peering between the border leaf nodes in each data center is the most appropriate solution as it allows for exchanging routing information between the two data centers. This ensures that the routes are properly distributed without the need for L2 bridging.

Option C:Configuring Type 5 EVPN routes is necessary for advertising IP prefixes (Layer 3 routes) across the EVPN. Type 5 routes allow for the exchange of IP prefixes between the two data centers, enabling the necessary routing functionality without the need for bridging.

Conclusion:

Option B:Correct—Peering between border leaf nodes sets up the necessary route exchange between data centers.

Option C:Correct—Type 5 EVPN routes are essential for exchanging Layer 3 prefixes between data centers.

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.

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 References:

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