There is only one reason people fail the CCNA or any other Cisco exam. No matter what they say such as:

Ran out of time Couldn't get the network up Didn't understand the question Nerves got the better of me Got stuck in multi-part question etc.

The reason for exam failure is lack of preparation. And before you get angry at me I failed my first attempt and it was due to lack of preparation. I still hadn't nailed subnetting (back in 2001) but decided to try my luck.

Five subnetting questions and one failure later I went home licking my wounds.

I've just gotten off the phone with one studend who has just failed and they are very dejected as you can imagine.

It was avoidable. I have written several articles on what you need to do in order to pass. The number one tip is to never attempt the real exam until you are getting 95% or more in your practise exams. Either with my deviously hard CCNA exams:

http://www.howtonetwork.net/products/item11.cfm

Or exams for some other quality provider (not that I know any other decent ones).

I spell it all out here:

http://www.howtonetwork.net/public/1153.cfm

Thanks

Paul