Windows Route Backup (useful for Windows Container usage like RKE2 where HNS configuration wipes the routes)

route_backup.ps1

# Route Backup
#
# Creates a script at C:\eth_routes.ps1 (or user Desktop) with `route add` statements to re-apply routing table entries of a specific interface.
#
# Useful for Windows Container usage like RKE and RKE2 Kubernetes, where HNS configuration wipes parts of the routing table.
# Related issue: https://projectcalico.docs.tigera.io/getting-started/windows-calico/troubleshoot#after-initializing-calico-for-windows-aws-metadata-server-is-no-longer-reachable

$ifname = "Ethernet"
$default_metric = 5

# determine if user has administrative privilege
$currentPrincipal = New-Object Security.Principal.WindowsPrincipal([Security.Principal.WindowsIdentity]::GetCurrent())
$is_admin = $currentPrincipal.IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)

$route_cmd_file = if ($is_admin) {
    "C:\eth_routes.ps1"
} else {
    $desktop_path = [Environment]::GetFolderPath("Desktop")
    Join-Path -Path $desktop_path -ChildPath "eth_routes.ps1"
}

$eth_ifindex = Get-NetAdapter -Name $ifname | select ifIndex -ExpandProperty ifIndex | select -first 1

$commands = @()
Get-NetRoute -InterfaceIndex $eth_ifindex | ForEach-Object {
    $metric = if ($_.RouteMetric -ne 0) { $_.RouteMetric } else { $default_metric }  # set default metric value if Get-NetAdapter returned metric 0
    $commands += "ROUTE -P ADD $($_.DestinationPrefix) $($_.NextHop) METRIC $($metric)"
}

$commands -join "`n" | Out-File -FilePath $route_cmd_file