Alternative Port Mappings

ComputerIntune-readyPol_AlternativePortMappings

Supported on At least Windows Server 2025, Windows 11

25H2 · 1.0

What it does

This policy setting determines the alternative port registry mappings used by the SMB client. If you enable this policy setting, the first valid mapping will be used if the mapping's server name matches the targeted server name for connectivity. If you enable this policy setting and do not specify at least one valid mapping, or if you disable or do not configure this policy setting, then the SMB client will refer to other methods of determining alternative port usage such as with the NET USE or New-SmbMapping commands. Examples: contososa.file.core.windows.net:tcp:448 edgesrv1.corp.contoso.com:quic:450 How to modify this setting: Arrange the desired alternative port mappings in the edit box with one mapping entry per line. The format of each mapping entry specifies a server name, transport type, and port number separated by colons as done so in the example above. Note: This policy does not require a Windows reboot to take effect.

What it writes

Hive: HKEY_LOCAL_MACHINE
Registry key: Software\Policies\Microsoft\Windows\LanmanWorkstation

In Intune

No native CSP; import the ADMX (Intune-ready).

From Microsoft's Policy CSP DDF files (DDF v2 Files, February 2026), read 18 Oct 2026.

Options

Option	Type	Registry value	Allowed values
Alternative Port Registry Mappings	Multi-line text	`AlternativePortMappings`	Any

Configure and deploy

Choose a state and the option values; the output below is generated from the template for exactly that.

Enabled · Computer · template defaults

Registry file (.reg)

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\LanmanWorkstation]
"AlternativePortMappings"=hex(7):00,00,00,00

PowerShell

$ErrorActionPreference = 'Stop'

function Set-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $PropertyType,
        [Parameter(Mandatory = $true)][object] $Value
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        New-Item -Path $Path -Force | Out-Null
    }

    New-ItemProperty -LiteralPath $Path -Name $Name -PropertyType $PropertyType -Value $Value -Force | Out-Null
}

function Remove-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (Test-Path -LiteralPath $Path) {
        Remove-ItemProperty -LiteralPath $Path -Name $Name -Force -ErrorAction SilentlyContinue
    }
}

function Clear-RegistryKeyValues {
    param(
        [Parameter(Mandatory = $true)][string] $Path
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return
    }

    foreach ($propertyName in (Get-Item -LiteralPath $Path).Property) {
        Remove-ItemProperty -LiteralPath $Path -Name $propertyName -Force -ErrorAction SilentlyContinue
    }
}

# Policy: Alternative Port Mappings
# Name: Pol_AlternativePortMappings
# Scope: Machine
# State: Enabled
# Source: LanmanWorkstation.admx

Set-RegistryValue -Path 'Registry::HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\LanmanWorkstation' -Name 'AlternativePortMappings' -PropertyType 'MultiString' -Value @()

The OMA-URI is an inferred ADMX-backed Policy CSP candidate derived from the source ADMX file name and policy name.
Some Microsoft policies use built-in Policy CSP pages whose area names don't match the ADMX file name, so verify the candidate against Microsoft Learn before deployment.
The generated payload is incomplete because one or more ADMX element values were not supplied: MultiText_AlternativePortMappings

ADMX profile candidate (OMA-URI)

./Device/Vendor/MSFT/Policy/Config/ADMX_LanmanWorkstation/Pol_AlternativePortMappings

Intune remediation scripts

Detection

$ErrorActionPreference = 'Stop'
$reasons = [System.Collections.Generic.List[string]]::new()

function Test-RegistryValueExists {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return $false
    }

    return $null -ne (Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction SilentlyContinue)
}

function Test-RegistryValueEquals {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $Kind,
        [Parameter(Mandatory = $true)][object] $Expected
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return $false
    }

    $valueObject = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction SilentlyContinue
    if ($null -eq $valueObject) {
        return $false
    }

    $actual = $valueObject.$Name
    switch ($Kind) {
        'String' { return [string]$actual -ceq [string]$Expected }
        'ExpandString' { return [string]$actual -ceq [string]$Expected }
        'DWord' { return [uint32]$actual -eq [uint32]$Expected }
        'QWord' { return [uint64]$actual -eq [uint64]$Expected }
        'MultiString' {
            $actualArray = @($actual)
            $expectedArray = @($Expected)
            if ($actualArray.Count -ne $expectedArray.Count) { return $false }
            for ($index = 0; $index -lt $actualArray.Count; $index++) {
                if ([string]$actualArray[$index] -cne [string]$expectedArray[$index]) { return $false }
            }
            return $true
        }
        'Binary' {
            $actualArray = [byte[]]$actual
            $expectedArray = [byte[]]$Expected
            if ($actualArray.Length -ne $expectedArray.Length) { return $false }
            for ($index = 0; $index -lt $actualArray.Length; $index++) {
                if ($actualArray[$index] -ne $expectedArray[$index]) { return $false }
            }
            return $true
        }
        default { return [string]$actual -ceq [string]$Expected }
    }
}

# Policy: Alternative Port Mappings
# Name: Pol_AlternativePortMappings
# Scope: Machine
# State: Enabled
# Source: LanmanWorkstation.admx

$isMatch = Test-RegistryValueEquals -Path 'Registry::HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\LanmanWorkstation' -Name 'AlternativePortMappings' -Kind 'MultiString' -Expected @()
if (-not $isMatch) {
    $reasons.Add('Value mismatch: HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\LanmanWorkstation\AlternativePortMappings') | Out-Null
}

if ($reasons.Count -eq 0) {
    Write-Output 'Compliant'
    exit 0
}

$reasons | ForEach-Object { Write-Output $_ }
exit 1

Remediation

$ErrorActionPreference = 'Stop'

function Set-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name,
        [Parameter(Mandatory = $true)][string] $PropertyType,
        [Parameter(Mandatory = $true)][object] $Value
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        New-Item -Path $Path -Force | Out-Null
    }

    New-ItemProperty -LiteralPath $Path -Name $Name -PropertyType $PropertyType -Value $Value -Force | Out-Null
}

function Remove-RegistryValue {
    param(
        [Parameter(Mandatory = $true)][string] $Path,
        [Parameter(Mandatory = $true)][string] $Name
    )

    if (Test-Path -LiteralPath $Path) {
        Remove-ItemProperty -LiteralPath $Path -Name $Name -Force -ErrorAction SilentlyContinue
    }
}

function Clear-RegistryKeyValues {
    param(
        [Parameter(Mandatory = $true)][string] $Path
    )

    if (-not (Test-Path -LiteralPath $Path)) {
        return
    }

    foreach ($propertyName in (Get-Item -LiteralPath $Path).Property) {
        Remove-ItemProperty -LiteralPath $Path -Name $propertyName -Force -ErrorAction SilentlyContinue
    }
}

# Policy: Alternative Port Mappings
# Name: Pol_AlternativePortMappings
# Scope: Machine
# State: Enabled
# Source: LanmanWorkstation.admx

Set-RegistryValue -Path 'Registry::HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\LanmanWorkstation' -Name 'AlternativePortMappings' -PropertyType 'MultiString' -Value @()

History 5 retained releases

24H2 · 1.030 Sep 2024
- Added in this release.

1 later release left it unchanged.

Template

Internal name: Pol_AlternativePortMappings
Namespace: Microsoft.Policies.LanmanWorkstation
Template file: LanmanWorkstation.admx
Release: Windows 11 25H2 · 1.0 · file set de4e49983ebd651f…

Definition, editor controls and support

Definition

<policy class="Machine" displayName="$(string.Pol_AlternativePortMappings_Name)" explainText="$(string.Pol_AlternativePortMappings_Help)" key="Software\Policies\Microsoft\Windows\LanmanWorkstation" name="Pol_AlternativePortMappings" presentation="$(presentation.Pol_AlternativePortMappings)" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="Microsoft.Policies.LanmanWorkstation:Cat_LanmanWorkstation" />
      <supportedOn ref="Microsoft.Policies.LanmanWorkstation:SUPPORTED_Windows_Server_2025_Windows_11_0" />
      <elements>
        <multiText id="MultiText_AlternativePortMappings" valueName="AlternativePortMappings" />
      </elements>
    </policy>

Editor controls

<presentation id="Pol_AlternativePortMappings" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
        <text>Alternative Port Registry Mappings:</text>
        <multiTextBox refId="MultiText_AlternativePortMappings" />
      </presentation>

Supported platforms and category

Microsoft.Policies.LanmanWorkstation:category:Cat_LanmanWorkstation
<category displayName="$(string.Cat_LanmanWorkstation)" name="Cat_LanmanWorkstation" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="Microsoft.Policies.Windows:Network" />
    </category>
Microsoft.Policies.LanmanWorkstation:definition:SUPPORTED_Windows_Server_2025_Windows_11_0
<definition displayName="$(string.SUPPORTED_Windows_Server_2025_Windows_11_0)" name="SUPPORTED_Windows_Server_2025_Windows_11_0" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      </definition>
Microsoft.Policies.Windows:category:Network
<category displayName="$(string.Network)" explainText="$(string.Network_Help)" name="Network" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
Microsoft.Policies.LanmanWorkstation:category:Cat_LanmanWorkstation
<category displayName="$(string.Cat_LanmanWorkstation)" name="Cat_LanmanWorkstation" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      <parentCategory ref="Microsoft.Policies.Windows:Network" />
    </category>
<strings><string id="Microsoft.Policies.LanmanWorkstation:Cat_LanmanWorkstation">Lanman Workstation</string></strings>
Microsoft.Policies.LanmanWorkstation:definition:SUPPORTED_Windows_Server_2025_Windows_11_0
<definition displayName="$(string.SUPPORTED_Windows_Server_2025_Windows_11_0)" name="SUPPORTED_Windows_Server_2025_Windows_11_0" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions">
      </definition>
<strings><string id="Microsoft.Policies.LanmanWorkstation:SUPPORTED_Windows_Server_2025_Windows_11_0">At least Windows Server 2025, Windows 11</string></strings>
Microsoft.Policies.Windows:category:Network
<category displayName="$(string.Network)" explainText="$(string.Network_Help)" name="Network" xmlns="http://schemas.microsoft.com/GroupPolicy/2006/07/PolicyDefinitions" />
<strings><string id="Microsoft.Policies.Windows:Network">Network</string><string id="Microsoft.Policies.Windows:Network_Help">Allows configuration of components of the operating system used by a client computer to connect to a network. This includes DNS settings and Offline Files.</string></strings>