How to Get the Speed and Duplex of a Network Adapter in Batch Script

@echo off
setlocal enabledelayedexpansion

set "AdapterName=Ethernet"

echo [AUDIT] Checking Link Speed for "%AdapterName%"...
echo.

:: Verify the adapter exists
set "found=0"
for /f "tokens=2 delims==" %%n in ('wmic nic get NetConnectionID /value 2^>nul') do (
    for /f "delims=" %%m in ("%%n") do (
        if /i "%%m"=="%AdapterName%" set "found=1"
    )
)

if !found! equ 0 (
    echo [ERROR] Adapter "%AdapterName%" not found.
    echo.
    echo Available adapters:
    wmic nic where "NetConnectionID is not null" get NetConnectionID 2>nul
    pause
    endlocal
    exit /b 1
)

:: Query for Speed in bits per second
:: Nested FOR strips invisible \r from WMIC output
set "raw_speed="
for /f "tokens=2 delims==" %%a in ('wmic nic where "NetConnectionID='%AdapterName%'" get Speed /value 2^>nul') do (
    for /f "delims=" %%b in ("%%a") do set "raw_speed=%%b"
)

:: Validate
if not defined raw_speed (
    echo [ERROR] Could not retrieve speed. Adapter may be disconnected.
    pause
    endlocal
    exit /b 1
)

:: Convert to Mbps using string manipulation
:: Batch set /a overflows above 2,147,483,647, a 10Gbps link (10000000000) would crash
:: Instead, slice off the last 6 digits to divide by 1,000,000
set "speed_len=0"
set "temp=!raw_speed!"
:CountLen
if defined temp (
    set "temp=!temp:~1!"
    set /a speed_len+=1
    goto :CountLen
)

if !speed_len! gtr 6 (
    set /a trim=!speed_len!-6
    set "mbps=!raw_speed:~0,%%trim%%!"
    :: Use PowerShell for reliable division since batch string math is fragile
    for /f %%m in ('powershell -NoProfile -Command "[math]::Round(%raw_speed% / 1000000)"') do set "mbps=%%m"
) else (
    set "mbps=0"
)

echo [RESULT] %AdapterName% Link Speed: !mbps! Mbps (!raw_speed! bps^)
echo.

:: Warn if below Gigabit
if !mbps! lss 1000 (
    if !mbps! gtr 0 (
        echo [WARNING] Adapter is NOT running at Gigabit speed!
        echo          Possible causes: damaged cable, bad switch port, or auto-negotiation issue.
    )
) else (
    echo [OK] Adapter is running at Gigabit speed or higher.
)

pause
endlocal

@echo off
setlocal

echo [REPORT] Detailed Network Link Capabilities...
echo.

powershell -NoProfile -Command ^
  "$adapters = Get-NetAdapter -ErrorAction SilentlyContinue;"^
  "if (-not $adapters) {"^
  "  Write-Host '[ERROR] No network adapters found.';"^
  "  exit 1"^
  "};"^
  "Write-Host ('  {0,-45} {1,-12} {2,-15} {3,-12} {4}' -f 'ADAPTER','STATUS','LINK SPEED','DUPLEX','MEDIA TYPE');"^
  "Write-Host ('  ' + '-' * 100);"^
  "$warnings = 0;"^
  "foreach ($a in $adapters) {"^
  "  $icon = if ($a.Status -eq 'Up') { '[OK]' } else { '[--]' };"^
  "  $speed = if ($a.LinkSpeed) { $a.LinkSpeed } else { 'N/A' };"^
  "  $duplex = if ($null -ne $a.FullDuplex) { if ($a.FullDuplex) { 'Full' } else { 'Half' } } else { 'N/A' };"^
  "  $media = if ($a.MediaType) { $a.MediaType } else { 'N/A' };"^
  "  Write-Host ('  {0} {1,-40} {2,-12} {3,-15} {4,-12} {5}' -f $icon, $a.Name, $a.Status, $speed, $duplex, $media);"^
  "  if ($a.Status -eq 'Up' -and $a.FullDuplex -eq $false) {"^
  "    Write-Host '       ^^^ [WARNING] Half Duplex detected - performance will be degraded!' -ForegroundColor Yellow;"^
  "    $warnings++"^
  "  };"^
  "  if ($a.Status -eq 'Up' -and $a.LinkSpeed -match '100 Mbps|10 Mbps') {"^
  "    Write-Host '       ^^^ [WARNING] Sub-Gigabit speed - check cable and switch port!' -ForegroundColor Yellow;"^
  "    $warnings++"^
  "  }"^
  "};"^
  "Write-Host ('  ' + '-' * 100);"^
  "if ($warnings -gt 0) {"^
  "  Write-Host '';"^
  "  Write-Host ('  ' + $warnings + ' warning(s) found. Investigate flagged adapters.') -ForegroundColor Yellow"^
  "} else {"^
  "  Write-Host '';"^
  "  Write-Host '  All active adapters are running at optimal speed and duplex.' -ForegroundColor Green"^
  "}"

pause
endlocal

@echo off
setlocal EnableDelayedExpansion

echo [NIC SUMMARY] All enabled network adapters
echo.

set "found=0"

:: Column width
set "nameW=40"
set /a truncW=nameW-3

echo   ADAPTER NAME                              SPEED (bps^)
echo   ================================================================

for /f "skip=2 tokens=2,3 delims=," %%A in ('wmic nic where "NetEnabled=True" get Name^,Speed /format:csv 2^>nul') do (
    
    set "adName=%%A"
    set "adSpeed=%%B"

    if defined adName if defined adSpeed (

        :: Trim leading spaces
        for /f "tokens=* delims= " %%X in ("!adName!") do set "adName=%%X"

        :: Truncate safely (FIXED)
        if "!adName:~%nameW%,1!" NEQ "" (
            set "adName=!adName:~0,%truncW%!..."
        )

        :: Pad for alignment
        set "spaces=                                        "
        set "paddedName=!adName!!spaces!"
        set "paddedName=!paddedName:~0,%nameW%!"

        echo   !paddedName! !adSpeed!
        set "found=1"
    )
)

echo   ================================================================

if !found! equ 0 (
    echo.
    echo   [WARN] No enabled adapters found.
)

pause
endlocal

@echo off
setlocal

set "OutputFile=%USERPROFILE%\nic_audit_%COMPUTERNAME%.csv"

echo [AUDIT] Exporting adapter speed data to CSV...
echo         File: %OutputFile%
echo.

powershell -NoProfile -Command ^
  "$results = @();"^
  "foreach ($a in (Get-NetAdapter -ErrorAction SilentlyContinue)) {"^
  "  $results += [PSCustomObject]@{"^
  "    Computer   = $env:COMPUTERNAME;"^
  "    Adapter    = $a.Name;"^
  "    Status     = $a.Status;"^
  "    LinkSpeed  = $a.LinkSpeed;"^
  "    FullDuplex = $a.FullDuplex;"^
  "    MediaType  = $a.MediaType;"^
  "    MacAddress = $a.MacAddress"^
  "  }"^
  "};"^
  "$results | Export-Csv -Path '%OutputFile%' -NoTypeInformation;"^
  "Write-Host ('[OK] Exported ' + $results.Count + ' adapter(s) to CSV.')"

pause
endlocal

for /f %%m in ('powershell -NoProfile -Command "[math]::Round(%raw_speed% / 1000000)"') do set "mbps=%%m"

for /f "tokens=2 delims==" %%a in ('wmic ... /value') do (
    for /f "delims=" %%b in ("%%a") do set "var=%%b"
)

wmic nic where "NetConnectionID is not null" get NetConnectionID