You might need to create static routes in your vSAN environment.
In traditional configurations, where vSphere uses a single default gateway, all routed traffic attempts to reach its destination through this gateway.
However, certain vSAN deployments might require static routing. For example, deployments where the witness is on a different network, or the stretched cluster deployment, where both the data sites and the witness host are on different networks.
To configure static routing on your ESXi hosts, use the esxcli command:
esxcli network ip route ipv4 add -g gateway-to-use –n remote-network
remote-network is the remote network that your host must access, and gateway-to-use is the interface to use when traffic is sent to the remote network.
For information about network design for stretched clusters, see Administering VMware vSAN.