iPhone-Dev Team has released Redsn0w 0.9.12b1 which has support for iOS 5.1.1 untethered jailbreak.If you have already jailbroken your device untether using Absinthe then you don’t need to jailbreak your device again.
Redsn0w 0.9.12b1 is also compatible with A5 devices which includes iPad 2,iPad, and iPhone 4S along with iPod Touch 3G/4G, Apple TV 2G, iPhone 4 (GSM & CDMA) and iPhone 3GS.
How to untether jailbreak iOS 5.1.1 using Redsn0w 0.9.12b1
1. Connect your device to your computer.
2. Download Redsn0w 0.9.12b1 and run.
3. Click on the option Jailbreak.
4. Enter DFU mode by following the on-screen instructions of Redsn0w.
To put your device in DFU mode you will be required to hold Power and Home buttons for 10 seconds simultaneously and then release Power button but hold Home button for more about 30 seconds.
5. Wait till the device restores and then resprings.
Your device is now untethered jailbroken on iOS 5.1.1 using Redsn0w.