netreg Revisited

Rob Riepel riepel at
Wed Apr 4 17:10:04 UTC 2012

Ditto here.  We regenerate dhcpd.conf every 10 minutes and restart whenever there are changes (which is almost every 10 minutes during the day - our IP management system has hundreds of users, so changes are frequent).  The servers are restarted one minute apart as it takes 10 seconds for dhcpd to digest the configuration and start doing its thing.  Works like a charm.

My only wish is a way to declare reserved leases in the config file.  (Maybe I've missed that?)

FWIW, our config file represents virtually the entire campus network and has ~1300 shared-networks and over 200k host statements.

On Apr 4, 2012, at 6:05 AM, Randall C Grimshaw wrote:

> Ditto, with the exception that we did use omapi in a captive portal implementation which required custom coded middleware to work around a memory leak in omapi.... thus I feel justified in avoiding omapi when possible.
> Randall Grimshaw rgrimsha at
> ________________________________________
> From: at [ at] on behalf of John Wobus [jw354 at]
> Sent: Friday, March 25, 2011 10:34 AM
> To: Users of ISC DHCP
> Subject: Re: netreg Revisited
> We rolled our own system years ago that's pretty
> much as you describe netreg and we have never
> changed from restarting dhcpd to using OMAPI.  I was
> influenced by an on-list dhcpd developer comment that
> they'd like to replace OMAPI, and also I was
> uncomfortable with host configs in the lease file
> rather than the config file.  Also, by regenerating
> the entire config file, we easily eliminate the
> possibility of dhcpd and our database getting out
> of synch.  But obviously OMAPI's worked very
> well for many sites, who probably laugh at the
> hoops we jump through to avoid using it.
> We run a redundant pair and we restart dhcpd every 2
> minutes when there are config changes awaiting
> deployment.  I think we assist ISC by exercising
> dhcpd in a somewhat-extreme manner.
> John Wobus
> Cornell
> On Mar 22, 2011, at 12:27 PM, Martin McCormick wrote:
>>      Some years ago, Carnegie Mellon University built a
>> clever use of dhcp and DNS called netreg to authenticate clients
>> who wanted to connect to their networks. It looks like nobody
>> has done much to it since about 2005 and there is no mention of
>> failover or omapi. All updates are done the old fashioned-way.
>> Modify dhcpd.conf. Stop the server. Say a prayer and restart
>> dhcpd.
>>      We've been asked to investigate netreg so I am asking
>> whether there is a modernized version that exists and makes use
>> of omapi for dynamic updates.
>>      The original idea was that each network had a small pool
>> of dynamic leases with very short lifetimes. A client is sent to
>> the authentication server and, if approved, he gets put in to
>> the known pool. By using omapi, he could also be given a bootP
>> entry if the magic between authentication and approval can do
>> that.
>>      We are basically looking to make sure we don't re-envent
>> any good wheels that have already been proven to roll.
>>      Thanks for all constructive ideas.
>> Martin McCormick WB5AGZ  Stillwater, OK
>> Systems Engineer
>> OSU Information Technology Department Telecommunications Services
>> Group
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