IPv6 Link local addresses and device identifier

Richard Siddaway Profile: Richard Siddaway

If I run ipconfig on my system the partial results are this

Wireless LAN adapter Wireless Network Connection:

   Connection-specific DNS Suffix  . : tiscali.co.uk
Link-local IPv6 Address . . . . . : fe80::6d95:b824:6a72:a0a9%11
IPv4 Address. . . . . . . . . . . : 192.168.1.2
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1

Ethernet adapter Local Area Connection:

   Connection-specific DNS Suffix  . :
Link-local IPv6 Address . . . . . : fe80::4547:ee51:7aac:521e%10
IPv4 Address. . . . . . . . . . . : 10.10.54.202
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . :

Notice that the IPv6 addresses have a % sign followed by a number.  This is the device id of the network adapter

If we modify our get-IPAddress function to output the adapter’s deviceid (Index on Win32_NetworkAdapterConfiguration class)

function get-IPAddress {            
[CmdletBinding()]            
 param (            
  [string]$computer="$env:COMPUTERNAME"            
 )            
  Get-WmiObject -Class Win32_NetworkAdapterConfiguration -ComputerName $computer | where {$_.IPAddress} |             
  foreach {            
  $address = $_.IPAddress[1]            
              
  Write-Debug "Test for ::"            
  if ($_.IPAddress[1].Contains("::")){            
   $blocks = $_.IPAddress[1] -split ":"            
   $count = $blocks.Count            
   $replace = 8 - $count + 1            
   for ($i=0; $i -le $count-1; $i++){            
    if ($blocks[$i] -eq ""){            
      $blocks[$i] = ("0000:" * $replace).TrimEnd(":")            
    }            
   }            
   $address = $blocks -join ":"            
  }            
            
  Write-Debug "Check leading 0 in place"            
  $blocks = $address -split ":"            
  for ($i=0; $i -le $blocks.Count-1; $i++){            
    if ($blocks[$i].length -ne 4){            
      $blocks[$i] = $blocks[$i].Padleft(4,"0")            
    }            
   }            
   $address = $blocks -join ":"            
            
   $ipconfig = New-Object -TypeName PSObject -Property @{            
     Description = $($_.Description)            
     IPv4Address = $($_.IPAddress[0])            
     IPv4Subnet = $($_.IPSubnet[0])            
     IPv6Address = $address            
     IPv6Subnet = $($_.IPSubnet[1])            
     DeviceId =  $($_.Index)            
   } | select Description, IPv4Address, IPv4Subnet, IPv6Address, IPv6Subnet, DeviceId            
   $ipconfig             
  }              
}

we get this output

PS> get-IPAddress
Description : NVIDIA nForce 10/100/1000 Mbps Networking Controller

IPv4Address : 10.10.54.202

IPv4Subnet  : 255.255.255.0

IPv6Address : fe80:0000:0000:0000:4547:ee51:7aac:521e

IPv6Subnet  : 64

DeviceId    : 7

Description : Atheros AR5007 802.11b/g WiFi Adapter

IPv4Address : 192.168.1.2

IPv4Subnet  : 255.255.255.0

IPv6Address : fe80:0000:0000:0000:6d95:b824:6a72:a0a9

IPv6Subnet  : 64

DeviceId    : 11

These device ids don’t match – whats going on.

If we use the MSNdis_EnumerateAdapter and MSNdis_EnumerateAdapterEX classes as in this function from http://msmvps.com/blogs/richardsiddaway/archive/2011/08/25/network-adapter-details.aspx

We can get the adapter details stored in the registry which uses a different set of indexes!!!

function get-adapter {            
param(            
 [string]$computer="."            
)            
Get-WmiObject -Namespace root\wmi -Class MSNdis_EnumerateAdapter `
-ComputerName $computer |            
foreach {            
 $nic = Get-WmiObject -Namespace root\wmi -Class MSNdis_EnumerateAdapterEx `
-ComputerName $computer -Filter "InstanceName = '$($_.InstanceName)'"            
            
$header = $nic.EnumerateAdapter.Header            
            
 New-Object -TypeName PSobject -Property @{            
  Computer = $_.__SERVER            
  Adapter = $_.InstanceName            
  Device = $_.DeviceName            
  Active = $_.Active            
  Index = $($nic.EnumerateAdapter.IfIndex)            
  NetLuid = $($nic.EnumerateAdapter.NetLuid)            
  Revision = $header.Revision            
  Size = $header.Size            
  Type = $header.Type            
 }            
}            
}

get-adapter | sort Index | Format-Table adapter, Index –AutoSize

produces (truncated output of)

Adapter                                               Index

——-                                               —–

NVIDIA nForce 10/100/1000 Mbps Networking Controller     10

Atheros AR5007 802.11b/g WiFi Adapter                    11

which matches the ipconfig results of

Ethernet adapter Local Area Connection:

Link-local IPv6 Address . . . . . : fe80::4547:ee51:7aac:521e%10

Wireless LAN adapter Wireless Network Connection:

Link-local IPv6 Address . . . . . : fe80::6d95:b824:6a72:a0a9%11

We can test the relationship between the registry and WMI device Ids

function resolve-deviceID {            
[CmdletBinding()]            
 param (            
  [string]$computer="$env:COMPUTERNAME"            
 )            
  Get-WmiObject -Class Win32_NetworkAdapterConfiguration -ComputerName $computer |             
  where {$_.IPAddress} |             
  foreach {            
   $nic = Get-WmiObject -Namespace root\wmi -Class MSNdis_EnumerateAdapterEx `
  -ComputerName $computer -Filter "InstanceName = '$($_.Description)'"            
               
   New-Object -TypeName PSObject -Property @{            
    Name = $($_.Description)            
    WMI_Index = $($_.Index)            
    Reg_Index = $($nic.EnumerateAdapter.IfIndex)            
   }             
 }            
}

Which produces this output

PS> resolve-deviceid | ft -a

Name                                                  Reg_Index WMI_Index

—-                                                  ——— ———

NVIDIA nForce 10/100/1000 Mbps Networking Controller         10         7

Atheros AR5007 802.11b/g WiFi Adapter                        11        11

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