Failover on a large DHCP system

Steve van der Burg steve.vanderburg at LHSC.ON.CA
Mon May 11 19:35:57 UTC 2009

15k leases here, with 15k host containers, also dynamically pushed (adds, edits, deletions) to the servers via omshell.  I don't bother sticking them in the conf as well though.  Instead, I parse the leases file to pull out the current state, diff that against what needs to be present and use omshell to make the changes.  A couple of pieces of perl code (perl + expect for the omshell stuff) do all the work once every 2 minutes (each server on alternating minutes) on a partner pair.

The host containers do *not* disappear from the leases file. Barring catastrophic disk failure, the leases file, although it gets rewritten faily often, should be considered as permanent as the conf file.


"Brad Dameron" <Brad.Dameron at> wrote:
> I use omapi with 3.1.1 currently with 38k active leases without any issues. I 
> add it to dhcp with omapi then I write it out to a global include file for 
> restarts. The reason you are seeing it after a restart is because it get's 
> wrote into the dhcpd.leases file. It will be removed from the lease file 
> after a few rotations. It's not immediately. We currently use a 24 hour lease 
> time. I haven't restarted my dhcp server in months and we add/remove statics 
> quite a bit. If someone gives me an idea of what they need in a script I can 
> convert my current perl script to be usable by the rest of the world.
> Brad
> ________________________________
> From: dhcp-users-bounces at on behalf of Nicholas F Miller
> Sent: Mon 5/11/2009 7:55 AM
> To: dhcp-users at 
> Subject: RE: Failover on a large DHCP system
> That was our original thought but after some testing and talk of 
> omapi's demise and memory leaks I am hesitant to go the omapi route. 
>  From our testing the changes made via omshell take precedence over 
> the config even after a restart. This could be a real headache for 
> trouble shooting. I think the best solution is to continue using 
> restarts to add and remove hosts from DHCP. I took a more 
> comprehensive look at our DHCP server and see that we only have around 
> 20,000 active leases during busy times and around 105,000 pool 
> addresses. From what people have been saying here that isn't all that 
> large of a load.
> _________________________________________________________
> Nicholas Miller, ITS, University of Colorado at Boulder
> On May 9, 2009, at 6:00 AM, dhcp-users-request at wrote:
>> You could do both -- use omshell to make the changes, but also update
>> dhcpd.conf.  That way you have the benefit of instant change without 
>> reload
>> and the security of a configuration file.
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> dhcp-users mailing list
> dhcp-users at 

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