Failover : Balancing a one-ip pool (!)

Nicolas Ecarnot nicolas at
Tue Feb 16 08:05:34 UTC 2016


This message is less a question than a discussion, because we're happy 
with our setup for years and maybe won't change soon, unless you answer 
with a nice new idea.

We have 7 DHCP servers in a star pattern : one central and 6 around.
The center is the primary peer for the others, for around 400 pools and 
lots of subnets.

Around 30 pools are classical ones, and balancing fine.
The numerous other ones are one-ip pools.

These one-ip pools are made this way in order to :
- benefit from failover setup. There seems to be no other way, failover 
can only be setup on pools
- apply classID rules by pool, working only on one machine by subnet. We 
don't want to use static reservations for that.

All this is working like a charm, but a small concern of mine is the 
periodic balancing (60 seconds by default, we raised it to 120) where I 
see that the servers are trying and obviously failing to balance the 
only one ip between peers.
This is not very bad, except it is eating CPU and flooding the logs.

But I post here this message in hope someone could advice a better way 
to do. Because I read lots of doc about balancing and the way ISC DHCPD 
is managing this sounds clever and I'd be happy to use it in a proper way.

Of course, external constraints exist forcing me to use this weird 
one-ip pools setup. But I'll fight to change them if someone replies 
with nice hints I may have missed.



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