Wednesday, July 29, 2009

Checking accessibility with online DNS tools

It appears that yesterday, SoftLayer had a DDoS attack on one of their DNS servers, though nothing official is confirmed yet.

SoftLayer is our hosting provider and a DDoS attack is a distributed denial of service action to make a resource unavailable, in this case a DNS server. Roughly explained, a DNS server is in charge with translating a domain name to an IP address, making it possible for a user to type a name like www.teamness.com in the browser address bar and get the proper web page back. Pingdom has a blog post called A visual explanation of how DNS lookups work, with a nice picture depicting the process.

All the above means that www.teamness.com wasn't accessible in some areas in the world, at least by the domain name. I tried a few websites that will let you use their DNS servers, to get an idea of where the website wasn't available. Here is the list with these services (I also included IP addresses, since if you have a DNS problem, you might not be able to access them by names):

Website by name: http://www.all-nettools.com/toolbox
Website by IP: http://216.92.207.177/toolbox
Location: United States - Pennsylvania - Pittsburgh

Website by name: http://www.dnsstuff.com/
Website by IP: http://66.36.247.82/
Location: United States - Texas - Dallas

Website by name: http://network-tools.com
Website by IP: http://67.222.132.196/
Location: United States - New Jersey - Ocean City

Website by name: http://ping.eu
Location: Germany - Berlin

Website by name: http://www.demon.net/external
Website by IP: http://194.159.246.194/external
Location: United Kingdom - Scotland - Aberdeen

Website by name: http://www.knossos.net.nz/checkdomain.cgi
Location: New Zealand - Auckland

I used http://whois.domaintools.com to get the locations.

The interesting thing is that www.teamness.com was accessible through all the above, but not from my machine in Sweden. I asked a friend from Cyprus who was up at that time to check it with nslookup and it didn't work from his machine either.

And people were on a re-twitting frenzy about the incident.

More links on the matter:

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