HSRP-like virtual DNS services.

[Phil Hoenig]

Hi all,

I'm looking at upgrading our DNS servers and, if possible, would like
to have some sort of redundacy set up such that if any one machine went
down the service itself would still continue. 

A possibility is to have two machines behind a load sharer of some
sort, but that load sharer itself then becomes a single point of
failure, so there'd have to be two of those. This leads to at least
four machines for each of our three services (which I want to keep
separate so that a DOS against one is not a DOS against the others) and
I'm not sure I can justify the resources to purchase, set up and
maintain a dozen machines. I'm also not sure how that sort of thing
would work when other very important services are on the same subnet
(it seemed like a good idea at the time - over a decade ago) and
changing the IPs of these services would be painful.

A DNS analogue to Cisco's HSRP seems like a good solution. Two DNS
servers each with their own IPs on the same subnet would pretend to be
a third, with the first doing all the work whilst the second monitors
the first and takes over should the first have any difficulties. I'd
imagine that there should be a wrapper script around named similar to
that mentioned in <http://www.isc.org/pubs/tn/isc-tn-2004-1.html> so
that a machine with DNS probems will appear to be a machine off the air
and that there'd have to be some work to keep these machines
synchronised and have their zone transfer request appear to come from the
virtual service.

Presumably this sort of thing's been done before but I can't find much
useful documentation on the matter. What term should I be Googling for?
(The hardware and OS haven't been purchased as yet so they can be
whatever's suitable.)

Thanks,

Phil Hoenig

-- 
Philip Hoenig                         | p.hoenig at its.unimelb.edu.au
Network Analyst                       | 
Information Technology Services       | When I grow up I want to be
University of Melbourne, Australia    | Chairman Kaga.