Wednesday, March 21, 2012

Checking NIC for collisions (speed/duplex mismatch) Windows Powershell

This is an old powershell v1 script that I came up with quite a long time ago. I'm sure it can be modified for easier and more robust usage. Since network card settings in the registry can be difficult to decode between vendors, the best way to look for speed/duplex issues is looking at collisions. Microsoft systems are not very details on networking errors, but they do keep track of this type of problem and it is available WMI. The script below pieces together two WMI classes to get the speed setting and looks for collisions.

Results in PSObject array of all NIC's
Computername        NicName                       LinkSpeed          Collisions
------------        -------                       ---------          ----------
MyComputer          Intel(R) PRO/100...                 100                   0

function get-NicError ([string]$server) {
 #This function uses WMI queries against the target machine to get link speed information and
 #check for any recorded network collissions.  It combines the two queries to print out collisions
 #per adapter with link speed.

 if ([string]::IsNullOrEmpty($server)) {
  write-host -foregroundcolor "yellow"  "Usage: get-NicError servername"
  write-host -foregroundcolor "yellow"  "   Get speed and collision details for network adapters"

 $result = @()

 $a = gwmi -namespace root\wmi -class msndis_ethernetmoretransmitcollisions -computername $server |select-object instancename,ndisethernetmoretransmitcollisions
 $b = gwmi -namespace root\wmi -class msndis_linkspeed -computername $server | select-object instancename,ndislinkspeed 

 if (($a -eq $null) -or ($b -eq $null)) {
  write-error "WMI connection error"

 foreach ($link in $b) {
  $link.ndislinkspeed = $link.ndislinkspeed / 10000

 foreach ($item in $a) {
   foreach ($seconditem in $b) {
    if ($item.instancename -eq $seconditem.instancename) {
      $myres = New-Object psobject
     Add-Member -InputObject $myres NoteProperty Computername $server
     Add-Member -InputObject $myres Noteproperty NicName $item.instancename
     Add-Member -InputObject $myres Noteproperty LinkSpeed $seconditem.ndislinkspeed
     Add-Member -InputObject $myres Noteproperty Collisions $item.ndisethernetmoretransmitcollisions
     $result += $myres

 return $result

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