# ============================================================================
# READ-ONLY INVENTORY SCRIPT
# ============================================================================
# Purpose
#   Enumerate virtual machine network configuration across all connected
#   vCenters (Enhanced Linked Mode supported).
#
#   For each VM NIC, output:
#     - VM name
#     - Guest FQDN (from VMware Tools)
#     - Portgroup / network name
#     - VLAN ID (or TRUNK for VDS trunks)
#     - IPv4 address
#     - Subnet mask
#     - Default gateway
#
# Safety
#   • READ-ONLY. No configuration changes are made.
#   • Uses Get-View exclusively to read inventory objects.
#   • No Set-*, Invoke-*, or Reconfig tasks.
#
# Data sources (important)
#   • NetworkName, VLAN        → vCenter configuration (reliable)
#   • IP, Subnet, Gateway,
#     FQDN                     → VMware Tools guest data (best available)
#   • If VMware Tools is absent or stale, guest fields will be blank.
#
# Assumptions
#   • You are already connected to one or more vCenters.
#   • Enhanced Linked Mode automatically expands scope.
#
# ============================================================================


# ----------------------------------------------------------------------------
# BUILD VLAN LOOKUP TABLES (ONCE)
# ----------------------------------------------------------------------------
# We pre-load VLAN information into hash tables so we don’t repeatedly query
# vCenter while iterating VMs. This keeps the script fast and predictable.

# --- Distributed vSwitch portgroups -----------------------------------------
# Key   : Portgroup name
# Value : VLAN ID, 'TRUNK', or 'UNKNOWN_VDS'
$vdsVlanByPg = @{}

Get-View -ViewType DistributedVirtualPortgroup `
         -Property Name, Config.DefaultPortConfig |
ForEach-Object {

    $name = $_.Name
    $vlanSpec = $_.Config.DefaultPortConfig.Vlan

    # Single VLAN ID
    if ($vlanSpec -is [VMware.Vim.VmwareDistributedVirtualSwitchVlanIdSpec]) {
        $vdsVlanByPg[$name] = $vlanSpec.VlanId
    }
    # VLAN trunk
    elseif ($vlanSpec -is [VMware.Vim.VmwareDistributedVirtualSwitchTrunkVlanSpec]) {
        $vdsVlanByPg[$name] = 'TRUNK'
    }
    # Anything else (rare but explicit)
    else {
        $vdsVlanByPg[$name] = 'UNKNOWN_VDS'
    }
}

# --- Standard vSwitch portgroups ---------------------------------------------
# Key   : Portgroup name
# Value : VLAN ID
$stdVlanByPg = @{}

Get-View -ViewType HostSystem `
         -Property Config.Network.Portgroup |
ForEach-Object {

    foreach ($pg in $_.Config.Network.Portgroup) {

        # Multiple hosts can expose the same portgroup name.
        # We only need one VLAN ID per unique name.
        if (-not $stdVlanByPg.ContainsKey($pg.Spec.Name)) {
            $stdVlanByPg[$pg.Spec.Name] = $pg.Spec.VlanId
        }
    }
}


# ----------------------------------------------------------------------------
# PULL VM INVENTORY (SINGLE API CALL)
# ----------------------------------------------------------------------------
# We request only the properties we actually use. This keeps Get-View fast
# even in large environments.

$vms = Get-View -ViewType VirtualMachine -Property `
    Name,
    Guest.HostName,
    Guest.Net,
    Config.Hardware.Device


# ----------------------------------------------------------------------------
# PROCESS EACH VM AND EACH NIC
# ----------------------------------------------------------------------------
foreach ($vm in $vms) {

    # Guest FQDN from VMware Tools (may be null)
    $fqdn = $vm.Guest.HostName

    # Extract only virtual Ethernet adapters from the VM hardware
    $vmNics = $vm.Config.Hardware.Device |
        Where-Object { $_ -is [VMware.Vim.VirtualEthernetCard] }

    foreach ($vmNic in $vmNics) {

        # Portgroup / network name as shown on the VM NIC
        $networkName = $vmNic.DeviceInfo.Summary

        # Resolve VLAN using lookup tables
        $vlan = $null
        if ($vdsVlanByPg.ContainsKey($networkName)) {
            $vlan = $vdsVlanByPg[$networkName]
        }
        elseif ($stdVlanByPg.ContainsKey($networkName)) {
            $vlan = $stdVlanByPg[$networkName]
        }

        # Match guest network info to this NIC via MAC address
        # This is the only reliable join between config and guest data.
        $guestNic = $vm.Guest.Net |
            Where-Object { $_.MacAddress -eq $vmNic.MacAddress }

        # --------------------------------------------------------------------
        # CASE 1: Guest network data exists (VMware Tools reported it)
        # --------------------------------------------------------------------
        if ($guestNic) {

            $gateway = $guestNic.Gateway

            # A single NIC can have multiple IPs.
            # Emit one row per IPv4 address.
            for ($i = 0; $i -lt $guestNic.IpAddress.Count; $i++) {

                $ip = $guestNic.IpAddress[$i]

                # Skip IPv6 to keep output clean and predictable
                if ($ip -like '*:*') { continue }

                $mask = $null
                if ($guestNic.SubnetMask.Count -gt $i) {
                    $mask = $guestNic.SubnetMask[$i]
                }

                [pscustomobject]@{
                    VMName         = $vm.Name
                    FQDN           = $fqdn
                    NetworkName    = $networkName
                    VLAN           = $vlan
                    IP             = $ip
                    Subnet         = $mask
                    DefaultGateway = $gateway
                }
            }
        }

        # --------------------------------------------------------------------
        # CASE 2: No guest network data (Tools missing or not reporting)
        # --------------------------------------------------------------------
        else {

            [pscustomobject]@{
                VMName         = $vm.Name
                FQDN           = $fqdn
                NetworkName    = $networkName
                VLAN           = $vlan
                IP             = $null
                Subnet         = $null
                DefaultGateway = $null
            }
        }
    }
}

# ----------------------------------------------------------------------------
# Example usage:
#
#   | Sort-Object VMName, NetworkName, IP
#   | Export-Csv .\vm_network_inventory.csv -NoTypeInformation
#
# ----------------------------------------------------------------------------