Each time an OEM like Samsung update their firmware some methods of rooting will not work. An example of this is the DoomLord – Easy Rooting Method. In this method I was able to root the Galaxy S 2 I9100 with DXKI2 firmware with one click but this method won’t work with the latest firmwares like the Android 2.3.6 DKL3.
The good news is that ChainFire, the GodFather of Samsung Galaxy S II rooting released a modified DXKL3 kernel. This kernel is already rooted and you have to do is push it via Odin. This method is for ‘rooting beginners‘ and if you just follow the instruction you will have a rooted device in few seconds.
Warning: Perform at your own risk, rooting could possibly brick your device and void your warranty.
Prerequisite before rooting are as follows:
Back up your entire system this includes Contact, SMS, Call Logs, Apps, Music, Pictures etc. You can follow some back up procedure and tools, Here:
Check your firmware: Settings > About Phone > Kernel Version e.g 126.96.36.199-I9100DXKL3-CL814816 (DX is the country code)