IPv4 Network Subnet Prefixes, Masks, Usable Hosts

The following table shows the IPv4 network subnet prefixes, subnet masks, and the number of usable hosts.

Prefix size Network mask Available subnets Usable hosts per subnet Total usable hosts
/24 255.255.255.0 1 254 254
/25 255.255.255.128 2 126 252
/26 255.255.255.192 4 62 248
/27 255.255.255.224 8 30 240
/28 255.255.255.240 16 14 224
/29 255.255.255.248 32 6 192
/30 255.255.255.252 64 2 128
/31 255.255.255.254 128 2 * 256

* for point-to-point links only

In a subnet the following two addresses cannot be assigned to hosts:

  • the first address is the address of the subnet,
  • the last address is the broadcast address to all hosts.

HP iLO is not responding

When during boot of an HP ProLiant server you see the “iLO2 not responding. System health monitoring has been disabled.” error message you need to restart the HP Integrated Lights-Out (iLO) component in the server.

iLo is a small, always on computer with a web interface to monitor and manage the hardware of the HP ProLiant servers. You can monitor the temperature sensors, fan speeds, power usage, and you can turn on and off the server remotely. So if you accidentally shut down the server or the server loses power and does not start automatically you can push the virtual power button on the web interface and turn on the server as if you would stand in front of it.

To restart iLO in the HP ProLiant server you have to completely discharge all electricity from the server.

  • shut down the server,
  • disconnect all power cords from the electrical outlets,
  • remove all power supplies from the server (you need to disconnect the power cord from the power supply too to remove the power supply),
  • press and hold the power button on the front of the server for 15-30 seconds,
  • re-install the power supplies,
  • connect the power cables to the power supplies,
  • connect the power cables to the electrical outlets,
  • momentarily press the power button on the front of the server to turn on the server.

This power reset does not erase any information of the iLO configuration, just restarts it.

On the power on screen you should see the usual messages from iLO.

There is already an open DataReader associated with this Command which must be closed first

When your MVC 5 web application page tries to read the database using the Entity Framework in a loop you may get the following error message:

InnerException: System.InvalidOperationException
HResult=-2146233079
Message=There is already an open DataReader associated with this Command which must be closed first.
Source=System.Data

This usually happens when a cshtml page receives an IEnumerable<> model from the database and makes repeated calls to retrieve the rows one-by-one in a foreach loop.

If your page does not display paged data, read the rows into a List  with the ToList() method and send the list to the cshtml page to iterate through it. This forces the application to read all appropriate rows with one call from the database.

Sometimes you can also eliminate the problem if you add the following to the connection string in the web.config file:

;multipleactiveresultsets=True

How to increase the security in a NetApp system

  • Use putty to connect to the IP address of the NetApp management port
  • Log in with the Login and Password

Start the System Console

  • at the SP …> prompt type system console

To change the root and naroot passwords

  • type passwd
  • for the Login: question enter root
  • enter the new password
  • enter the new password again for verification
  • This step changes booth the root and naroot passwords.

To enable auditing

  • To check the current auditing status enter options cifs.audit
  • To enable auditing enter options cifs.audit.enable on
  • To automatically save the audit log enter
    • options cifs.audit.autosave.ontime.enable on
    • options cifs.audit.autosave.onsize.enable on
  • The file will be saved at /etc/log/adtlog.evt

To exit the System Console

  • Press Ctrl-D to exit the System Console
  • To see all events of the filer enter  events all

To exit the filer

  • Type exit to close the session

Head tracking with a web camera and FaceTrackNoIR

FaceTrackNoIR is a free open source head tracking device to detect the movement of your head in simulation games.

In a web browser go to http://facetracknoir.sourceforge.net/information_links/download.htm

  • Download the full installer
  • Run the SetupFaceTrackNoIR_Full_v170.exe
  • On the select components page uncheck the Protocol for Virtual Jostick(s) in the Interface to games section. You don’t need it now.

In a web browser go to http://www.faceapi.com/Download/register.php

  • Fill out the registration form and open your email for the activation link.
  • Click the Click here to continue link
  • Select the Non-Commercial faceAPI link to downolad the head tracking API
  • Double click the FaceTrackingAPI_NC-V3.2.6.zip
  • Allow the extraction of the included files
  • Install all features the setup_faceTrackingAPI_NC_V3.2.6.exe

In a web browser go to http://sourceforge.net/projects/facetracknoir/?source=dlp

  • Download and install the SetupFaceTrackNoIR_Full_v170.exe file
  • Copy the headtracker folder to C:\Program Files\Eagle Dynamics\DCS World\bin (sorry I have to research the source of the “headtracker” folder)

Activate the head tracking

  • Double click the FaceTrackNoIR icon on your desktop to start the face tracking application
  • In the Profile group click the Load button.
  • In the  C:\Program Files\Eagle Dynamics\DCS World\bin\headtracker folder select the DCS_A10C.ini file
  • In the Global Settings group set the Smoothing to 20
  • In the Filter group set the filter to Accelera filter Mk2
  • On the Options menu select Keyboard and Mouse Shortcuts
  • For Center select the Middle mouse button
  • Click the Start button to start head tracking

Windows web service authentication in IIS Express

When you develop a SOAP web service in Visual Studio 2013 the IDE uses IIS Express for testing. To set up Windows authentication in IIS Express follow the steps below:

Create a Local Security Group on your computer

  • Right click Computer and select Manage
  • On the left side expand Local Users and Groups
  • Right click the Groups folder and select New Group
  • Create a group with the name WebserviceUsers for the users of the web service
  • Right click the Users folder and select New User
  • Create a user and add it to the WebserviceUsers security group

Add the following lines to the  <system.web> section of the Web.config file of your web service application

<authentication mode=”Windows”/>
<authorization>
<allow roles=”WebserviceUsers”/>
<deny users=”*”/>
</authorization>

Set up IIS Express for Windows authentication

  • Select the web service project in the Solution Explorer
  • In the View menu select Properties Window
  • Disable Anonymous Authentication and enable Windows Authentication
    Visual Studio IIS Express Windows Authentication Properties Window

 

In the caller application call the web service with user name and password

  • Add the following lines to your class to supply the credentials
private Webservice.Service _Webservice = new Service();

// Constructor
public Business() {
    string webserviceUrl = "Webservice_Url";
    string webserviceUserName = "Webservice_UserName";
    string webservicePassword = "Webservice_Password";
    _Webservice.Url = webserviceUrl;
    ICredentials credentials = new NetworkCredential(webserviceUserName, webservicePassword);
    _Webservice.Credentials = credentials;
}

How to sign in to your Windows 8 PC without an email address

When you set up Windows 8 the Sign in to your PC page asks you for your email address. It is you computer you should be able to use it without telling Microsoft your email address and other personal information.

To use you computer without giving away your email address

  • At the bottom of the the Sign in to your PC screen select Sign in without a Microsoft account
  • On the next screen select the Local Account button
  • Enter a User name and a Password

 

How to remove Windows 8 and install Windows 7 on a Toshiba Satellite p50-A series laptop

If you want to remove the preinstalled Windows 8 from a new Toshiba Satellite P50-AST3GX2 laptop you need a Windows 7 DVD. You can buy the  Windows 7 DVD at Amazon.

The first step is to turn off UEFI in the BIOS and enable the legacy boot. This will allow the computer to boot from the Windows 7 DVD.

To enter the BIOS

  • Insert the Windows 7 DVD into the DVD drive
  • Completely turn off the laptop to access the Toshiba BIOS Setup. When you select “Shut down” on the Windows 8 screen the computer only goes to hibernation mode. To completely shut down Windows 8 follow the steps in  How to completely shut down Windows 8.
  • Press the power button and continuously tap the F12 button to open the boot menu
  • In the boot menu select Enter Setup and press Enter

Turn off the UEFI boot mode in the BIOS

  • In the BIOS setup select the Security tab on the top of the screen
  • Press Enter on the Secure Boot option and select Disabled
  • Select the Advanced tab on the top of the screen
  • Press Enter on the System Configuration
  • Press Enter on  Boot Mode and select CSM Boot

Save the BIOS settings

  • Press the F10 key on the keyboard
  • On the Exit Saving Changes window press Yes to save the changes
  • The computer restarts

Install Windows 7

  • The computer will boot from the Windows 7 DVD
  • Select Install, Advanced installation
  • Delete all partitions on the hard drive
  • Create one partition (Windows will create another 100MB system partition for itself)
  • Select the large partition as the destination of Windows 7

Windows 7 drivers

How to completely shut down a Windows 8 computer

As I found out the hard way when you select “Shut down” on the Power icon in the lower right corner of the Windows 8 screen the computer does not really shut down, it only goes to hibernation mode. This cheat is the trick behind the “fast boot” of Windows 8. This is great if next time you want to start Windows 8 fast. If you really want to shut down Windows 8 completely to access the boot menu of the computer you have to jump through a few absolutely illogical hoops:

Option 1

  • Log into Windows 8
  • Press Ctrl-Alt-Del on the keyboard
    win 8 shutdown ctrl-alt-del
  • In the lower right corner of the screen click the Power icon
  • Press the Shift key on the keyboard and select Restart (not Shut down!!!!)
    win 8 shutdown shift-restart
  • On the next page select Turn off your PC
    win 8 shutdown turn off pc

Option 2

  • On the Windows 8 Start screen open the Settings charm in the lower right corner
  • Click the Power icon
  • Press the Shift key on the keyboard and select Restart (not Shut down!!!)
    win 8 shutdown start page power button
  • On the next page select Turn off your PCwin 8 shutdown turn off pc

How to remove Windows 8 and install Windows 7 on a Dell inspiron 7000 series laptop

If you want to remove the preinstalled Windows 8 from a new Dell inspiron 7000 series (7537) laptop you need an external USB DVD drive and a Windows 7 DVD. You can buy the LG external USB DVD drive for $40 at Best Buy, and the Windows 7 at Amazon.

The first step is to turn off UEFI in the BIOS and enable the legacy boot. This will allow the computer to boot from the Windows 7 DVD.

To enter the BIOS

  • Turn off the laptop
  • Press the power button and continuously tap the F12 button to open the boot menu
  • In the Other Options section of the boot menu select Setup

Turn off the UEFI boot mode in the BIOS

  • In the BIOS setup select Boot on the top of the screen
  • Press Enter on the Secure Boot option and select Disabled
  • Press Enter on the Load Legacy Option Rom and select Enabled
  • Press Enter on the Boot List Option and select Legacy

Save the BIOS settings

  • Select Exit on the top of the screen
  • Select Exit Saving Changes and press Enter
  • Press Enter on Yes to save the changes

The computer will automatically try to restart and displays a message that “Operating system not found”

  • Keep the power button pressed to force it to shut down

Boot from the Windows 7 DVD

  • Insert the Windows 7 DVD into the DVD drive
  • Start the computer with the power button and continuously tap the F12 button to open the boot menu
  • If there is a + sign next to the CD/DVD/CD-RD Drive option select it and press Enter
  • If there is no plus sign next to it turn off the computer with the power button and try to start it again while tapping the F12 key

Install Windows 7

  • The computer will boot from the Windows 7 DVD
  • Select Install, Advanced installation
  • Delete all partitions on the hard drive
  • Create one partition (Windows will create another 100MB system partition for itself)
  • Select the large partition as the destination of Windows 7

Enjoy the last usable Windows version.