Find-DuplicateRoutes - PowerShell to identify with a split VPN has started duplicating routes to internal IP address but going around the VPN, resulting in stalled connections. (llama3:70b)

Find-DuplicateRoutes.ps1

function Find-DuplicateRoutes {
    # Get all network routes
    $routes = Get-NetRoute
    
    # Filter out default routes, link-local multicast routes, and link-local unicast routes
    $filteredRoutes = $routes | Where-Object { 
        (-not ($_.DestinationPrefix -eq '0.0.0.0/0')) -and 
        (-not ($_.DestinationPrefix -eq '::/0')) -and 
        (-not ($_.DestinationPrefix -like 'ff00::/8*')) -and 
        (-not ($_.DestinationPrefix -eq 'fe80::/64'))
    }

    # Group remaining routes by their DestinationPrefix
    $groupedRoutes = $filteredRoutes | Group-Object -Property DestinationPrefix
    
    # Identify groups where RouteMetric is not always unique
    $duplicateRoutes = @()
    foreach ($group in $groupedRoutes) {
        $routeMetrics = $group.Group | Select-Object -ExpandProperty RouteMetric
        if (($routeMetrics | Measure-Object -Maximum).Count -lt $group.Count) {
            $duplicateRoutes += [PSCustomObject]@{
                DestinationPrefix = $group.Name
                DuplicateEntries = $group.Group
            }
        }
    }
    
    # Display the duplicate routes if found
    if ($null -ne $duplicateRoutes -and $duplicateRoutes.Count -gt 0) {
        Write-Host "The following duplicate routes were found (excluding default, link-local multicast, and link-local unicast routes):"
        foreach ($route in $duplicateRoutes) {
            Write-Host "Destination Prefix: $($route.DestinationPrefix)"
            $route.DuplicateEntries | Select-Object InterfaceAlias, DestinationPrefix, NextHop, RouteMetric, PolicyStore | Format-Table -AutoSize
        }
    } else {
        Write-Host "No duplicate routes found (excluding default, link-local multicast, and link-local unicast routes)."
    }
}
function Find-DuplicateRoutes {
    # Get all network routes
    $routes = Get-NetRoute
    
    # Filter out default routes, link-local multicast routes, and link-local unicast routes
    $filteredRoutes = $routes | Where-Object { 
        (-not ($_.DestinationPrefix -eq '0.0.0.0/0')) -and 
        (-not ($_.DestinationPrefix -eq '::/0')) -and 
        (-not ($_.DestinationPrefix -like 'ff00::/8*')) -and 
        (-not ($_.DestinationPrefix -eq 'fe80::/64'))
    }

    # Group remaining routes by their DestinationPrefix
    $groupedRoutes = $filteredRoutes | Group-Object -Property DestinationPrefix
    
    # Identify groups where RouteMetric is not always unique
    $duplicateRoutes = @()
    foreach ($group in $groupedRoutes) {
        $routeMetrics = $group.Group | Select-Object -ExpandProperty RouteMetric
        if (($routeMetrics | Measure-Object -Maximum).Count -lt $group.Count) {
            $duplicateRoutes += [PSCustomObject]@{
                DestinationPrefix = $group.Name
                DuplicateEntries = $group.Group
            }
        }
    }
    
    # Display the duplicate routes if found
    if ($null -ne $duplicateRoutes -and $duplicateRoutes.Count -gt 0) {
        Write-Host "The following duplicate routes were found (excluding default, link-local multicast, and link-local unicast routes):"
        foreach ($route in $duplicateRoutes) {
            Write-Host "Destination Prefix: $($route.DestinationPrefix)"
            $route.DuplicateEntries | Select-Object InterfaceAlias, DestinationPrefix, NextHop, RouteMetric, PolicyStore | Format-Table -AutoSize
        }
    } else {
        Write-Host "No duplicate routes found (excluding default, link-local multicast, and link-local unicast routes)."
    }
}