Data Center Interconnect (DCI)

The ability to interconnect multiple EVPN fabrics is critical to the evolution of the Dell Enterprise SONiC networking operating system. With version 4.1, multiple EVPN fabrics that are geographically separated can now be interconnected.

In a DCI deployment, Layer 2 domains stretch across Performance Optimized Datacenters (PODs) while restricting the tunnels to each VTEP within the same site. Border gateways in each site create two types of tunnels, internal and external. The internal tunnel is created between local VTEPs for intrasite traffic, and an external tunnel with a remote site for intersite traffic.

There are several strategic benefits that DCI provides:

1. EVPN fabric expansion based on open standards.
2. Legacy environment integration, with EVPN, the ability for virtual environments to reach or communicate with nonvirtualized applications is important. DCI allows these connections while maintaining the benefits of a virtualized environment.

The following figure shows one of two DCI interconnects models. This model shows the interconnect originating at the spine layer. This model allows VxLAN tunnels to stretch across multiple PODs within same or different geographic locations.

The characteristics of this model are as follows:

• Workload mobility across any POD
• VxLAN EVPN control plane stretching across PODs
• Sharing of Layer 4 - Layer 7 services across PODs
• Recommended for active/active data center use cases

The second model in the following figure shows the interconnect originating at the leaf layer, or edge leaf switches. This model allows VxLAN tunnels to be terminated locally in each POD shown in gray. The tunnels do not exit the PODs unlike the previous model.

The characteristics of this model are as follows:

• Each POD is a distinct Availability Zone (AZ), providing failure domain isolation.
• Each POD runs a distinct Internal Gateway Protocol (IGP) and BGP-EVPN instance.
• Optionally, Layer 2 domains can be stretched across PODs.
• Recommended for active/backup data center use cases.