DATA CENTERS

  • 02/15/2007
    3:43 PM
  • Network Computing
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Breaking DNS with Wildcard records

Charter Communication???s wildcard DNS resolution maybe useful to users surfing the web through a browser, but will break all other IP applications. Error handling needs to be performed locally by the application receiving the error. Handling errors in the network...
Charter Communication???s wildcard DNS resolution maybe useful to users surfing the web through a browser, but will break all other IP applications. Error handling needs to be performed locally by the application receiving the error. Handling errors in the network for application traffic causes more problems that they solve. Using wildcard domain names to handle unresolved hosts is bad engineering. Period.

In DNS, there is a one to one or one to many relationship between host names and IP addresses. Wildcard domain names are special cases in the DNS which resolve any unmatched host name to an IP address and are only used when a more specific host name doesn't exist. For example, lets say that you have a zone that resolves www.example.com to your web server, mail.example.com to your mail server, and dns.example.com to your dns server. The host name *.example.com could be defined to resolve to www.example.com. If a user tries to access support.example.com, the name would resolve to www.example.com but mail.example.com would be unaffected.

Unfortunately, in a fit of trying to do the right thing, some ISP's, Charter Communications is just the latest culprit, are using wildcard DNS records to redirect users to an error page , which looks an awful lot like a HTTP 404 page.

Charter Communications About page says "This service automatically eliminates many of the error pages you may encounter as you surf the web." Unfortunately, Charter Communications that the application requesting name resolution is a web browser.


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