Introduction to VXLAN

Agenda:

• Evolution of Data Center Network Design
• Legacy Data Center Challenges
• Why CLOS Fabric?
• VXLAN Benifits
• What is VXLAN?

The Evolution of Data Center Network Designs

Traditionally, data centers used a 3-tier architecture. While effective in its time, it now faces significant limitations.

The modern approach uses a 2-tier CLOS fabric design, which addresses many of the challenges faced by the legacy 3-tier architecture.

Legacy DataCenter Challenges

In the old data center, there are multiple challenges and limitations, here's a look of some of key challenges:

1. Unused Linkes: Due to Spanning Tree Protocol (STP), many links are blocked to prevent loops, leading to underutilized resources, such as 10 Gig, 40 Gig, or 100 Gig ports.

2. Convergence Time: STP can take significant time to reconverge after a link failure, disrupting business operations.

3. Suboptimal Forwarding: STP often leads to inefficient routing by blocking ports to prevent loops.

4. Brodcast Storm: Broadcast storms can severely impact network performance and reliability.

5. No endpoint Mobility: VLAN limitations at Layer 3 boundaries hinder the extension of Layer 2 connections, reducing flexibility.

Why CLOS Fabric

Before diving into VXLAN, it’s essential to understand the benefits of the CLOS topology (Spine-Leaf):

• 3 Hop Between Endpoints: Only three hops are needed for any endpoint to reach its destination, ensuring low latency and high performance.

• Scale Out Architecture: Adding more Spines Switches increases physical path redundancy (High Resilency), adding more Leafs count without increasing oversubscription ratio (More Access Ports).

• High Resilience: If one spine fails, the traffic is rerouted through other spines, ensuring no impact on services.

• Support Modern Application: As data center traffic has shifted to east-west (within the data center), the CLOS fabric provides high bandwidth and low latency.

• Controlleed Oversubscription: The new design allows precise calculation and adjustment of the oversubscription ratio.

VXLAN Benfits:

1. Equal Cost Multi-Path (ECMP): Unlike STP, VXLAN allows all paths to be active, maximizing bandwidth usage.
2. Seamless VM mobility: VMs can move freely within the data center without reconfiguring the network.
3. Scalability and Flexibility: VXLAN supports up to 16 million segments due to its 24-bit identifier.
4. Workload Deployment: Simplified workload deployment across the data center, unrestricted by VLAN limitations.
5. Secure Multi-Tenancy: Traffic between tenants and segments is securely isolated within the fabric.

What is VXLAN?

VXLAN is a network virtualization technology widely used on large data center deployment, it is used to extend across Layer 2 network over Layer 3 IP network.

Key Points to Undersstand VXLAN:

1. Overlay vs. Underlay

• Underlay Network: The physical Layer 3 IP network responsible for VTEP (VXLAN Tunnel Endpoint) reachability.

• Overalay Network: A virtual network running on top of the physical underlay network.

2. VXLAN Topology:

• Utilizes the Leaf/Spine (CLOS-based) topology with Layer 3 links between leaf and spine switches. There is no direct connectivity between leaf switches or between spine switches.

3. VXLAN Header Structure:

• VXLAN uses a 24-bit identifier, allowing for up to 16 million segments.

• UDP Header: Indicates VXLAN encapsulation using ports 8472 or 4789, The destination port in the UDP header indicates that the packet is a VXLAN encapsulated packet. Therefore, both ports may be seen in different VXLAN implementations.
• Outer IP Header: The source IP address in the outer IP header is the local VTEP address. The destination IP address is the remote VTEP address for known unicast traffic for the associated multicast group address in the event of broadcast, unknown unicast, and multicast traffic. The encapsulated packets are routed through the underlay transport network according to the outer header IP addresses.
• Outer MAC address or Layer 2 header:?Used to forward encapsulated packets to the next hop device.

VXLAN revolutionizes data center networking by providing scalability, flexibility, and efficiency far beyond traditional methods. Ready to transform your network infrastructure with VXLAN? Let’s connect and explore the possibilities!

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