DNS is so powerful and important that any tool which advances its understanding is worth considering. Here is an online site where you can find common DNS problems, and do live timing testings for DNS server response [record type is selectible], WHOIS loolup and search, deobfuscate URLS, do IP testing right down to CIDR/Netmask lookup, and implement hostname tests.
Since it can be reached through the Net, it is an excellent resource for at-home DNS exercises.
Posted by jho at July 12, 2003 11:52 AM