Useful links for studying CCNA and good reminders.

http://routersimulator.certexams.com/router-labs/index.html

http://www.proprofs.com/quiz-school/story.php?title=ccna-practice-exam

http://www.howtonetwork.net/public/department98.cfm

http://www.howtonetwork.net/public/department140.cfm
http://gtcc-it.net/billings/VLSM.htm