linked. most contracts say that a penalty fee will be paid if either party does not stick to the contract (of the fixed rate in the case of the bank),so if interest goes up, the bank will see which is economically more viable. leaving you on the fixed interest rate, or pay the penalty and change your contract to linked. banks are not nice guys, they are there to make as much money off you as they can. So you get it fixed at 12%, interst rate shoots up to 17.5%... your fixed interest is cancelled and becomes linked should the prnalty works out cheaper than the loss of income in term of the interest rate.this is a protection mechanism for banks to curb the effects hyper inflation.
Zimbabwe for example: in 1999 you bought a car. you have your interest fixed at 15% so your monthly repayment was 10 000 zim dollars, in the year 2003 10 000 zim dollars would not even buy bread, so your car payments would be less than a loaf of bread - banks are not going to take a hit like this, and will adjust your fixed to link should the interest rate rise.