vSAN Stretch Cluster Layer 3 witness configuration

Products

• VMware vSAN

Issue/Introduction

This KB provides guidance with configuring the witness appliance / physical host for layer 3 (L3) network routing to ensure proper witness traffic communication between the witness appliance and the data sites.

Environment

vSAN OSA & ESA stretch clusters (All Versions)

vSAN OSA & ESA 2-node stretch clusters (All Versions)

Layer 3 network

Cause

When the witness appliance and the data sites reside in separate networks static route(s) need to be configured on the witness host to ensure proper witness traffic routing between the witness appliance and the data hosts.

For example, deployments where the witness is on a different network or the vSAN stretched cluster deployment where both the data sites and the witness host are on different networks require static routes.

Resolution

Configuring static route(s) on the witness appliance:

1. Deploy the witness appliance 
   
   
2. Create the static route to the data sites on the witness appliance with the below command:
   
   esxcli network ip route ipv4 add -g gateway-to-use –n remote-network

Example: esxcli network ip route ipv4 add -g 10.###.###.1 -n 10.###.###.112/29


3. From Cluster > Configure > vSAN > Fault Domains manually configure the stretch cluster to add the witness appliance to the cluster
   
   Note: If the static route was not added to the witness appliance before configuring the stretch cluster the witness appliance will be network partitioned from the cluster. An indicator that the static route was not added to the witness appliance prior to configuring the stretch cluster is the process taking a long time to complete.
   
   To fix this add the static route to the witness appliance. Disable then re-enable the stretch cluster.

Additional Information

Routing and Switching Requirements
Configuration of Network from Data Sites to Witness Host