IOS 5.1 upgrade error: This device is not eligible for the requested build

Mar 11, 2012   //   by NG   //   IOS and iPhone Tips  //  No Comments

While upgrading IOS 5.1 on my iphone 4S via iTunes 10.6 (relased specificly for new ipad 3and IOS 5.1), I faced error as “This device is not eligible for the requested build” . My iphone was not jailbroken and is running absolutely fine, even the inbuilt (Settings > General > Software Update) ios upgrade was not working, so I went to Apple online help and find troubleshooting tips on link under section “Specific error messages and resolutions”.


I figured out that error I was facing was due to hosts file issue, as per apple –  If you have installed software to perform unauthorized modifications to your iOS device, that software may have redirected connections to the update server ( within the Hosts file. First you must uninstall the unauthorized modification software from the computer, then edit out the “” redirect from the hosts file, and then restart the computer for the host file changes to take affect.  For steps to edit the Hosts file and allow iTunes to communicate with the update server, see iTunes: Troubleshooting iTunes Store on your computer, iPhone, iPad, or iPod—follow steps under the heading Blocked by configuration (Mac OS X / Windows) > Rebuild network information > The hosts file may also be blocking the iTunes Store. If you do not uninstall the unauthorized modification software prior to editing the hosts file, that software may automatically modify the hosts file again on restart. Also, using an older or modified .ipsw file can cause this issue. Try moving the current .ipsw file, or try restoring in a new user to ensure that iTunes downloads a new .ipsw.

To modify hosts file, follow following guidelines provided by Apple,



The hosts file may also be blocking the iTunes Store.

  1. Open the Terminal utility located in Applications > Utilities.
  2. When Terminal opens, open the hosts file by typing entering the following command and pressing Enter:
    sudo nano /private/etc/hosts
  3. Type your user password when prompted.
    Note: This requires a non-blank admin password.
  4. Edit the hosts file:
    The hosts file contains some comments (lines starting with the # symbol), as well as some default hostname mappings (e.g. – localhost).
    You can navigate the file using the arrow keys.
  5. If an entry is found containing, add # and a space to the beginning of that line.
    Note: If this is a work system, the hosts file may be used to redirect to local resources, such as software updates. Consult your support resources.
    An example hosts file in Terminal
  6. Save the hosts file. 
    • When done editing the hosts file, press Control-o to save the file.
    • Press Enter on the filename prompt, and Control-x to exit the editor.

When I hashed the appropriate entry in my hosts file and tried updating IOS, it worked absolutely fine. Hope you may find the solution useful.


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