Well,i know this is a known trick but since i searched and didn't find it i decided to post[however,if it has been posted before please delete my post]
I know that many people have problems with their hosts and cant login to servers where host is required.But with a little trick you can connect ;)
So first of all you need a patched system[just download a system from any server you want,it will work]
Then download L2File edit[this is a link for interlude/kamael,if you want for c4/c5 search the forum and u will find :P]
http://rapidshare.com/files/103772796/L2_FileEdit__Int-Kamael_.rar.html
Open L2FIle edit and go to your system and open l2.ini [as shown in the ss]
http://i164.photobucket.com/albums/u28/megahaker/l2filedit.jpg
And edit it as follows:Go to the line where it says ServerAddr= and delete what is next to it
[for example if it says ServerAddr=72.233.81.58 l2authd.lineage2.com delete 72.233.81.58 l2authd.lineage2.com]
Open the hosts of the server you want to play using notepad and copy the ip of the server example 92.265.82.56 l2authd.lineage2.com
Then paste it next to the ServerAddr= [it will look like this ServerAddr=92.265.82.56 l2authd.lineage2.com
After this,press file<save and encrypt<save and select harder version 413
That's it!Now you can connect to the server u want with l2.exe!
This works to most of the servers i tried.Hope you find it useful!:D