<DllImport("iphlpapi.dll", EntryPoint:="GetAdaptersInfo", CharSet:=CharSet.Ansi)> _
    Private Shared Function GetAdaptersInfo( _
    ByVal pAdapterInfo As IntPtr, _
    ByRef pBufOutLen As UInt64) As Int32
    End Function

Sample Code:

    Public Sub GetAdapters()
    Dim structSize As Int32 = Marshal.SizeOf(GetType(IP_ADAPTER_INFO))
    Dim pArray As IntPtr = Marshal.AllocHGlobal(structSize)

    Dim len As UInt64 = Convert.ToUInt64(structSize)
    Dim ret As Int32 = GetAdaptersInfo(pArray, len)

    If ret = 111 Then
        ' Buffer was too small, reallocate the correct size for the buffer.
        pArray = Marshal.ReAllocHGlobal(pArray, New IntPtr(Convert.ToInt64(len)))
        ret = GetAdaptersInfo(pArray, len)
    End If

    If ret = 0 Then
        ' Call succeeded
        Dim pEntry As IntPtr = pArray
        Do
           ' Retrieve the adapter info from the memory address.
        Dim Entry As IP_ADAPTER_INFO = CType(Marshal.PtrToStructure(pEntry, GetType(IP_ADAPTER_INFO)), IP_ADAPTER_INFO)
        pEntry = Entry.Next
        Loop Until IntPtr.op_Equality(pEntry, IntPtr.Zero)
    End If

    Marshal.FreeHGlobal(pArray)
    End Sub