Need help on delegation to subdomain/external servers

RUOFF LARS Lars.Ruoff at
Thu Sep 17 16:05:28 UTC 2009


> [mailto:bind-users-bounces at] On Behalf Of Kevin Darcy
> > I have a hot-swap redundant system where 1 out of 2 servers 
> is active 
> > at any given time and the other is standby. DNS is 
> (mis?-)used to tell 
> > the clients which one is active at a given moment.
> > The idea is that clients resolve a name of the server and 
> the result 
> > is the address of the server that is currently active. (Only the 
> > current active server responds to DNS queries for its own name).
> >   
> DNS isn't really suited to this.

I guess you are right, but that's how the system works. (it's not me who
designed it)
It's the only viable way to find out which one is active at a given

> > The server uses TTL=0 in order to inhibit any caching on clients.
> >   
> I hope this stays on a private network then, because TTL=0 is 
> considered quite anti-social on the Internet. It makes 
> everyone who queries your nameservers work significantly 
> harder than they should.

It stays on a private network. :)

BTW, at the moment I am experimenting a solution usign a forward zone:
zone "dummy.ts" IN {
	type forward;
	forward only;
	forwarders {;; };

It seems to work.
I guess that the requests are not sent simultaneously though?
What delay do I have to expect when only the second server (
is active?
What search policy is applied by default? (round-robin vs sequential?)
Can I modify it?
Obviously I would prefer a policy where we always forward to the last
active, unless we time out; Then try the alternate.
Will check that out.


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