Try this:
Dim oInfo As System.Diagnostics.ProcessStartInfo = New System.Diagnostics.ProcessStartInfo("ipconfig", "/all")
oInfo.UseShellExecute = False
oInfo.ErrorDialog = False
oInfo.CreateNoWindow = True
oInfo.RedirectStandardOutput = True
Dim p As Process = System.Diagnostics.Process.Start(oInfo)
Dim oReader As System.IO.StreamReader = p.StandardOutput
RichTextBox1.Text = oReader.ReadToEnd()
oReader.Close()
End Dim