How do you recognize the attainment of enlightenment?

In the Buddhist story of Ananda, Buddha's most devoted disciple, it's said that after Buddha's death the first Buddhist council was assembled to write down all of Buddha's teachings. Only those that were enlightened could attending the council. As the person who was closest to the Buddha, Ananda knew best the teachings of the Buddha, but because he wasn't enlightened he could not attend. So Ananda started an intense meditation and became enlightened just before the council took place. How did he knew he became enlightened? How do you recognize when your practice finally brings you enlightenment?