PowerCLI: retrieve VMhost routes used for stretched VSAN clusters.

When configuring a stretched VSAN cluster, the VSAN VMkernel interface is connected to the “default” netstack and manual routes must be added which point to VSAN subnet gateways, which enables VSAN communication in a stretched cluster configuration. Without the additional routes add to the ESXi-hosts, communication to the witness appliance and the remote site is not working.

This script below shows the manual added routes of each ESXi host (vmhost) in the VSAN-enabled cluster.

This really helps when doing stretched VSAN cluster troubleshooting!

Below a small explanation of the script (for the techies):

First retrieve the all ESXi hosts from the selected VSAN enabled cluster:

$vmhosts = ((Get-Cluster).where({$_.VsanEnabled -eq $true}) |  Out-GridView -Title "Select VSAN Stretched cluster" -PassThru) | Get-VMHost 

Creating a loop for all ESXi hosts and retrieve the required information from each individual host:

foreach ($vmhost in $vmhosts) {
#retrieve default netstack default gateway
$vmhostgw = $vmhost.ExtensionData.Config.Network.IpRouteConfig.DefaultGateway
#retrieve VSAN VMkernel interface details
$vsanvmk = Get-VMHostNetworkAdapter -VMHost $vmhost | ? {$_.VsanTrafficEnabled -eq $True}

#create variables for IP, SubnetMask and Subnet
$vsanIP = [IPaddress]$vsanvmk.IP
$vsansubnet = [IPaddress]$vsanvmk.SubnetMask
$vsanlocalsubnet = ([IPAddress] (([IPAddress] $vsanvmk.IP).Address -band ([IPAddress] $vsanvmk.SubnetMask).Address)).IPAddressToString

#retrieve VMhosts routes
$vmhostroutes = Get-VMHostRoute -VMHost $vmhost 

The idea here is to filter the route list, filtering out IPv6-routes, local attached subnets and the default gateway route.

$vmhostipv4routes = $vmhostroutes.Where({$_.Gateway -like "*.*"}) #IPv4 filter
$vmhostipv4routes = $vmhostipv4routes.Where({$_.Gateway -ne "0.0.0.0"}) #local attached filter
$vmhostunknownroutes = $vmhostipv4routes.Where({$_.Gateway -ne $vmhostgw})#defaul gw filter

The results is a $vmhostunknownroutes variable which (prosumbaly) contain all manual added VSAN routes. It collects all routes and display them per host.

$vsanremotesubnets = @()
    foreach ($route in $vmhostunknownroutes) {
        $routegw = [IPaddress]$route.Gateway.Address
        if (($routegw.Address -band $vsansubnet.Address) -eq ($vsanip.Address -band $vsansubnet.Address)) {$vsanremotesubnets += $route}
    }
    write-host $vmhost "has the following vsan (remote) routes: "$vsanremotesubnets

and finally close the foreach loop

}

below the whole script. ENJOY!

$vmhosts = ((Get-Cluster).where({$_.VsanEnabled -eq $true}) |  Out-GridView -Title "Select VSAN Stretched cluster" -PassThru) | Get-VMHost 
foreach ($vmhost in $vmhosts) {
    $vmhostgw = $vmhost.ExtensionData.Config.Network.IpRouteConfig.DefaultGateway
    $vsanvmk = Get-VMHostNetworkAdapter -VMHost $vmhost | ? {$_.VsanTrafficEnabled -eq $True}
    $vsanIP = [IPaddress]$vsanvmk.IP
    $vsansubnet = [IPaddress]$vsanvmk.SubnetMask

    $vsanlocalsubnet = ([IPAddress] (([IPAddress] $vsanvmk.IP).Address -band ([IPAddress] $vsanvmk.SubnetMask).Address)).IPAddressToString

    $vmhostroutes = Get-VMHostRoute -VMHost $vmhost 
    $vmhostipv4routes = $vmhostroutes.Where({$_.Gateway -like "*.*"})
    $vmhostipv4routes = $vmhostipv4routes.Where({$_.Gateway -ne "0.0.0.0"})
    $vmhostunknownroutes = $vmhostipv4routes.Where({$_.Gateway -ne $vmhostgw})
    $vsanremotesubnets = @()
    foreach ($route in $vmhostunknownroutes) {
        $routegw = [IPaddress]$route.Gateway.Address
        if (($routegw.Address -band $vsansubnet.Address) -eq ($vsanip.Address -band $vsansubnet.Address)) {$vsanremotesubnets += $route}
    }
    write-host $vmhost "has the following vsan (remote) routes: "$vsanremotesubnets
}

I’m trying to create a script which creates all (missing) routes based on the locally attached subnets (of the VSAN enabled VMK-interface) of all hosts. Check my blog for future updates!