Many people are seeking to jailbreak iPhone 4S 5.1.1 in order to get iPhone 4s unlock, and it is complained by many visitors on my blog that RedSn0w is not jailbreaking iPhone 4s on iOS 5.1 or ios 5.1.1 (although it is not compatible with them). If you only need an unlock for your iPhone 4s there is another alternative solution and that is GEVEY™ Ultra S for GSM iPhone 4S. Below I have given you the paragraph from Applenberry website. Also you can watch below video to better understand how does this work.
“The GEVEY Ultra S GSM unlocks your GSM iPhone 4S. It’s a true plug-and-play unlock for GSM iPhone 4S running iOS 5.0, 5.0.1, 5.1 and 5.1.1. The GEVEY Ultra S is a thin microprocessor that sits between your network SIM card and the base-band hardware, allowing you to use your GSM iPhone 4S on all worldwide GSM networks.”
If you are already having Gevey S SIM on iPhone 4s 5.1 you can upgrade to iOS 5.1.1 since the existing SIM is compatible with 5.1.1 as well.