resilient designs for reaching root servers
Simon Waters
Simon at wretched.demon.co.uk
Fri Jul 12 20:49:59 UTC 2002
Herb wrote:
>
> I have two BIND 8.2.2 servers, S and T. 50% of my resolvers ("group A") list
> S first in resolv.conf and then T, and the other 50% ("group B") the other
> way. S and T are secondaries for an internal domain (both fwd and reverse
> zones). Both S and T can query the internet dns for answers. S and T do not
> supply internal info to the Internet.
>
> If the wire that links (say) S to the Internet is cut, external queries from
> group A will not be answered (unless they're already in S's cache).
But S returns SERVFAIL, and then the clients ask T for the
answer, don't they? Try it!
Depending on the resolver libraries in use in groups A and B,
they may query either server first - order listed is not
required to be strickly followed. DNS clients do all sorts of
different things.
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