[CentOS] DHCP server failover: advise is needed

Dear Experts,

I was running ISC DHCP server for longer than I would care to remember. 
Now I decided to climb out of the cave and configure failover set 
(primary-secondary), and I seem to hit brick wall, which I need help 
with. I only need IP v4, no v6, which may simplify things.

Could someone point to a description of working DHCP failover configuration?

I do not want to make two independent DHCP servers handling half of the 
pool each. We are not that rich as far as IP space is concerned.

I am not married to ISC DHCP server, so any one I will do, because:

<rant>
My current configuration is something that was gradually migrated and/or 
adjusted through several generations of systems, and server versions 
over the years. It works. When I tried to incorporate what I need for 
failover following ISC documentation, and some people's guides, I 
discovered, I need more sophisticated structure of sections and 
subsections, which I figured out finally. But the annoying part was: in 
ISC documentation I failed to find general stricture of which section 
can appear inside which; like:

a {
  b {
   c {

   }
  }
}

You can create each of sections/subsections following documentation, but 
to put them together making consistent config file you (I at least) have 
to figure on your own which section goes inside of which.
</rant>

So, I am not married to ISC DHCP server, we didn't get along now as far 
as my use of documentation is concerned. Anything that works - with 
failover! I am going to have it set up on FreeBSD, but if something 
works on Linux, I likely will be able to reproduce it on FreeBSD.


Thanks in advance for all your answers!

Valeri
-- 
++++++++++++++++++++++++++++++++++++++++
Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247
++++++++++++++++++++++++++++++++++++++++