Override transferred zone information?

Kevin Darcy kcd at daimlerchrysler.com
Fri Jan 5 01:20:59 UTC 2007

Eric Jain wrote:
> Just found the GeoDNS patch, seems like a great solution to a problem we 
> have (people linking to and bookmarking mirror web sites).
> There is one problem, though: We use an external secondary DNS server 
> (easyDNS.com), which does not support GeoDNS. easyDNS uses automatic zone 
> transfers to keep itself up to date, so I was wondering if it is possible 
> to get BIND to return fallback zone information that easyDNS can understand 
> (e.g. a simple round robin setup on the secondary DNS would be fine)?
"Simple round robin" isn't going to give you the "geo" functionality you 
seem to be striving for.

Not sure what you mean by "fallback zone information" either. There's no 
way within the protocol to say "prefer answers for a given zone from 
this set of nameservers, otherwise fall back to this other set". Is that 
what you meant? Unfortunately, iterative resolvers will typically prefer 
*faster* nameservers over slower ones, so presumably the easyDNS servers 
are getting a lot more queries for your zones than your own nameservers 
are (if not, perhaps you aren't getting your money's worth). Which 
means, all other things being equal, even if you implement GeoDNS on 
your servers, Internet clients will get the non-"geo"'ed answers more 
often than not.

If you want to provide the "geo" functionality in any consistent way, I 
think you need to *force* the answers to come from your own 
authoritative nameservers rather than the easyDNS ones. You could 
accomplish this by either taking your whole zone(s) in-house from 
easyDNS or by just delegating certain subzones from easyDNS-managed 
zones, e.g. delegate www.example.com from example.com, and run those 
with GeoDNS.

                                 - Kevin

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