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Getting Started With Versa SDWAN SD-WAN Overlay Topologies

February 13, 2023

Getting Started With Versa SDWAN
SD-WAN Overlay Topologies

What is Versa SDWAN?
Versa SD-WAN is a software-defined networking solution that provides centralized control and management of a wide area network (WAN) to optimize network performance and reduce costs. It enables businesses to manage their network traffic across multiple locations and cloud services using a unified platform, while also offering security features like encryption and firewall protection.

Versa Networks SD-WAN overlay topologies
Below are the various Versa Networks SD-WAN overlay topologies

⭐Full mesh 
⭐Hub and spoke 
⭐Regional mesh 
⭐Multi-VRF, or multitenancy

These topologies are created using well-known routing algorithms that have been in use by MPLS Layer 3 VPN networks for a long time. To accomplish fine-grained route management and to offer versatile choices for modifying and fine-tuning routes, they employ MP-BGP communities. These topologies may be built using Director Workflows, which will make these complicated configurations simpler.

Full-Mesh Topology
Any-to-any communication takes place using a full-mesh topology. This topology uses overlay tunnels for direct branch-to-branch communication and does not require traffic to transit a hub.

When branches must interact directly with one another, a full-mesh topology is typically the recommended topology.

Full-Mesh Topology Versa SDWAN
Fig 1.1- Full-Mesh Topology Versa SDWAN

A full-mesh topology is usually preferred over a hub-and-spoke topology for voice applications, since the hub is distant from the branches in a hub-and-spoke topology. 

Additionally, a distributed security architecture that enforces policy at the branch would benefit from a full-mesh topology. Using a full-mesh topology, traffic can be inspected without having to be funneled to hubs.

In a full-mesh topology SLA monitoring probes are sent to every remote branch on every available transport. 

SLA monitoring probes are used to track reachability and connection metrics for each access circuit pointing to a certain distant site. In big deployments, SLA optimization technologies like as adaptive SLA and data-driven SLA may be used to improve the SLA burden.

Hub-and-Spoke Topology
The only prefixes advertised by a hub-to-hub topology are hub routes by default, and spoke routes are not re- advertised by the hub branch. A topology like this is used when no communications are required between spokes.

According to the BGP community configuration, spoke prefixes are accepted by the hub but rejected by other spokes.

Versa Hub and spoke topology
Fig 1.2- Versa SDWAN Hub and Spoke topology

On hubs, all spokes prefixes are installed in the corresponding VRF. You can implement redistribution policy on hubs to perform route summarization or to generate default a static route, for instance, to attract traffic from spokes.

Regional mesh 
In the Regional Mesh, you group hub and branch devices by region. Within a particular region, the topology can be anything full mesh, partial mesh, or hub and spoke and branches communicate based on the selected topology. 

When a branch in one region wants to communicate with a branch in another region, the communication transits through regional hubs.

Versa SDWAN Regional topology
Fig 1.3- Versa SDWAN Regional topology

You can select this topology when there is geographical separation and when regional WAN transport networks are available and hubs between regions use the company backbone or high-bandwidth WAN links. 

Multi-VRF (Multitenant)
The Versa Networks SD-WAN solution is highly flexible and allows you to define and establish different topologies at the VRF, or tenant, level. 

Multi-VRF Topology Versa SDWAN
Fig 1.4- Versa SDWAN Multi-VRF topology

The default Versa SD-WAN model provisions a full forwarding mesh using IP prefix advertisement in MP-BGP. You can configure the VPN topologies discussed in previous sections using Director Workflows. 

SD-WAN topology with two VRFs in one organization. VRF-A (red) is configured as full meshed and VRF-B (blue) also uses a full-mesh topology. This principle can apply to multitenant branches in which each organization's topology may be different