[Q] Catch-all host in DNS

Kevin Darcy kcd at daimlerchrysler.com
Wed Jan 18 01:49:57 UTC 2006


Netfortius wrote:

>Could someone be kind enough to point me to some good documentation as to how 
>and what about catch-all host in DNS? I am interested in fundamentals, as 
>much as implementation. 
>
>I have been suggested by a blog vendor to implement a catch-all host on my 
>name servers, but I am not sure how this would work, as far as the purpose 
>for such from a blog stand point (but this would be a second question, 
>unrelated to DNS, of course ;)).
>
Depends on exactly what you mean by "catch-all host". If you mean just 
serving up an address for arbitrary-name-here.example.com, then you can 
implement that fairly simply using the wildcard feature of DNS, e.g. "* 
a 1.2.3.4" in the zonefile, assuming example.com is the origin. Anything 
that is explicitly defined in the example.com zone will override the 
wildcard entry.

If by "catch-all host" you mean that some community of clients resolves 
*all* non-existent names to a particular address, then the wildcard 
approach is not compatible with allowing those clients to resolve 
Internet DNS names, since it's not feasible to duplicate the entire 
Internet namespace in order to override the wildcard in all cases. This 
approach would only be useful on a small internal network, in which case 
you could just put the wildcard into the internal root zone and all 
other zones, if any, in the namespace.

- Kevin





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