All three sites in a stretched cluster communicate across the management network and across the vSAN network. The VMs in all data sites communicate across a common virtual machine network.

Following are the vSAN stretched cluster routing requirements:

Table 1. Routing Requirements

Site Communication

Deployment Model

Layer

Routing

Site to Site

Default

Layer 2

Not required

Site to Site

Default

Layer 3

Use static routes or gateway override.

Site to Witness

Default

Layer 3

Use static routes or gateway override.

Site to Witness

Witness Traffic Separation

Layer 3

Use static routes or gateway override when using an interface other than the Management (vmk0) interface.

Site to Witness

Witness Traffic Separation

Layer 2 for two-host cluster

Static routes are not required.

Virtual Switch Requirements

You can create a vSAN network with either vSphere Standard Switch or vSphere Distributed Switch. Use a distributed switch to prioritize bandwidth for vSAN traffic. vSAN uses a distributed switch with all the vCenter Server versions.

The following table compares the advantages and benefits of a distributed switch over a standard switch:

Table 2. Virtual Switch Types
Design Requirement Option 1 - vSphere Distributed Switch Option 2 - vSphere Standard Switch Description
Availability No impact No impact You can use either of the options
Manageability Positive impact Negative impact The distributed switch is centrally managed across all hosts, unlike the standard switch which is managed on each host individually.
Performance Positive impact Negative impact The distributed switch has added controls, such as Network I/O Control, which you can use to guarantee performance for vSAN traffic.
Recoverability Positive impact Negative impact The distributed switch configuration can be backed up and restored, the standard switch does not have this functionality.
Security Positive impact Negative impact The distributed switch has added built-in security controls to help protect traffic.