Data-center CLOS fabric architectures have become a standard design option for building new-generation data center networks. With Multiprotocol Border Gateway Protocol (MP-BGP) Ethernet VPN (EVPN) technology, a Virtual Extensible LAN (VXLAN) is a standout tool for network virtualization overlay deployments in data center fabrics.

VXLAN provides the following benefits:

• Multi-tenancy
• Seamless VM Mobility
• Overcomes limitation of 4K VLANs by using VNI (up to 16M VNIs could be used)
• Efficient use of bandwidth - Leverages ECMP for optimal path usage over the underlay network
• Flexibility: Workload can be extended anywhere. Any VLAN can be extended to any Leaf switch using VXLAN EPVN overlay over the L3 underlay. (Although it is worth mentioning that extending L2 is often a poor design choice.)
• Scalability: Leaf-Spine architecture can be easily scaled up by adding new Spines/Leaves

The Cisco NX-OS VXLAN Fabric design option recommends VXLAN EVPN NX-OS Multi-Site Architecture. Multi-Pod Fabrics are still valid designs and are supported by Cisco TAC, but you will not find them in the Nexus 9000 White Paper list https://www.cisco.com/c/en/us/products/switches/nexus-9000-series-switches/white-paper-listing.html.

Highlighted below are some of the Multi-Pod design challenges:

• Scalability issue. Multi-Pod requires "full-mesh" End-to-End VXLAN tunnels between Leaf devices, which leads to a scalability limit of the number of leaf switches in a Multi-Pod environment
• Single Overlay Control Plane. EPVN Updates are propagated End-to-End between Leaf devices
• Single Underlay Control Plane. To provide VTEP-to-VTEP reachability, information about loopbacks must be propagated through the whole Multi-Pod domain

Multi-Site design solves the above challenges by providing the following:

• Scaling by adding new VXLAN EVPN sites. L2 and L3 services can be extended between sites
• Multiple isolated Underlay Control Plane domains. Loopback reachability is required only within sites; no need to advertise loopback IP addresses between sites
• Multiple Overlay Control Plane domains. Overlay routing information is exchanged between Lead and BGW within the site and between BGWs of different sites
• Multiple BUM replication domains. Propagation of BUM traffic can be controlled by configuring storm-control features on Border Gateway devices

Multi-site use-cases:

• Scaling single Data Center
• Data Center Interconnect (DCI) for VxLAN fabrics
• DCI capability for the legacy 3-Tier DC networks via vPC Border Gateway devices
• Migration from Legacy 3-Tier networks to VxLAN/EVPN via vPC Border Gateway devices

We provide 8X5 Technical support till one month after the completion of the term.