Broadcom and Arista unify data center networks

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Broadcom and Arista have jointly introduced a unified network fabric for data centers. It is intended to make virtual and physical servers consistently reachable and manageable within the network.

Managing physical and virtual workloads in data center networks remains complex. Traditionally, two fabrics exist side-by-side: VMware NSX with the GENEVE overlay protocol for virtual workloads, and in current physical architectures, an EVPN/VXLAN fabric for control and data plane. However, consistent security policies must be established across both architectures, and connectivity and performance must be ensured. This represents a significant operational effort, especially in larger environments.

The Unified Network Fabric aims to eliminate this separation. To achieve this, Broadcom and Arista are integrating VCF with the Universal Cloud Network (UCN), merging physical and virtual workloads into a common EVPN/VXLAN fabric. The control plane exchanges reachability/routing information via EVPN, while user data traffic flows through VXLAN in the data plane.

Connection via Transit Gateway and Route Controller

VCF connects its virtual workloads to the Arista fabric via a so-called Transit Gateway – the connection element for Virtual Private Clouds (VPCs) introduced with VCF 9.0. The Transit Gateway receives the necessary reachability/routing information from the VCF Route Controller (RC), which maintains a Multiprotocol BGP (MP-BGP) peering with the Arista EVPN Gateways. Both sides exchange routing information through this peering.

In EVPN fabrics, tenant separation is achieved through virtual routing instances and so-called L3VNIs. In the Unified Fabric, the administrator assigns the appropriate Transit Gateway to each L3VNI. The diagram illustrates this coupling using L3VNI 10000 as an example. The 1:1 mapping between routing instance and Transit Gateway ensures tenant separation, scalability, and simple management.

Route Exchange and Data Path

To enable the Arista fabric to reach the virtual workloads, the VCF Route Controller distributes corresponding host routes (/32 for IPv4 or /128 for IPv6) as EVPN Type 5 route information, including the host IP address and the Tunnel Endpoint (TEP) IP address for the VXLAN tunnel, to the Arista EVPN Gateways. Optionally, the EVPN Gateway can aggregate these host routes to relieve the fabric's routing tables in larger environments. In the reverse direction, the Arista EVPN Gateways report subnet prefixes or a default route per routing instance to the Route Controller.

Based on this information, the respective ESXi TEP encapsulates the user data into a VXLAN tunnel and sends it to the Arista EVPN Gateway. This gateway forwards the packets through the appropriate L3VNI to the target VTEP (Leaf Switch) in the EVPN fabric. Consequently, a continuous VXLAN tunnel between the ESXi host and the leaf switch is not created; the EVPN Gateway acts as a re-encapsulation point between the virtual and physical worlds.

Unified View for Operations

Through the EVPN routing information, the administrator can also identify the TEP at which a workload is located within a single routing environment – without having to go through proprietary interfaces.

Additionally, Arista CloudVision and VCF Operations consolidate telemetry, topology, and configuration data from both worlds into a common interface. This allows for cross-domain error analysis and change management. For daily operations, this aspect is likely as important as the control plane mechanics themselves.

Availability and Use Cases

The Unified Network Fabric is initially available as a Tech Preview in VCF 9.1; general availability and the licensing model are still pending, according to Broadcom. The approach is likely to be of interest for brownfield migrations and mixed tenant environments where two separate fabrics currently run in parallel. A prerequisite remains a certified switch fabric – multi-vendor scenarios are fundamentally possible via the open EVPN Type 5 interface, but the initial focus is on Arista integration.

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