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List:       dhcp-users
Subject:    Re: Mixing fixed-address host declations in dhcpd.conf with dynamic entries created via omapi
From:       Kristian Pedersen <kristian.pedersen () vejen-net ! dk>
Date:       2012-07-17 13:41:58
Message-ID: 50056BA6.8060609 () vejen-net ! dk
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On 07/17/2012 02:00 PM, Steve van der Burg wrote:
> > We are implementing a new provisioning system that needs to signal our
> > dhcp-server to create or remove fixed-address host entries. The
> > provisioning system will quite frequently be doing updates, so omapi
> > would be nice to avoid having to restart the dhcp service.
> > 
> > On the other hand we use more than one dhcp server for redundancy and to
> > avoid these servers getting "out of sync" due to updates while one or
> > more servers are down, I would like to generate a completely updated
> > dhcpd.conf with all the static host entries. I could generate the config
> > as part of the dhcp startup script so im sure dhcpd.conf is always
> > accurate at service start.
> > 
> > So the question goes, how does the dhcp server handle overlaps in
> > dhcpd.conf vs. dynamic entries in dhcpd.leases? When the server starts
> > up and checks the dhcpd.leases, will any config in dhcpd.conf override
> > the ones from the lease-file? Do you see any problems in this
> > implementation or have suggestions for other ways to implement this?
> You can consider the leases file to be another configuration file, since the server \
> reads it when it starts up.  A system that I set up and that also manages host \
> entries (20,000+) does it this way (this is a block comment lifted right out of my \
> code): 
> # The basic strategy is:
> #
> # - Build list of MACs (with assoc. IP addrs for some) from the database,
> #   assuming that we'll be adding them all
> # - Build list of host objs from the server's lease file.  Assume that we'll be \
> deleting them all # - Compare lists:
> #         - remove 'host-delete' from the host list when we find a match in the \
> database list #         - remove 'db-add' when the database record matches the host \
> object #         - change 'db-add' to 'db-update' when changes have been made (db \
> needs to update host object) #         - leave 'db-add' alone when it really is a \
> new record # - Use omshell to run the updates to the servers
> 
> 'host-delete', 'db-add' and 'db-update' refer to actions that will be taken for \
> each host object. 
> In order for this to work, you need to have your DHCP servers send their lease \
> files to a central spot.  If a server has been down for, say, 8 hours, when it \
> starts up again, 8 hours of changes will be applied. 
> ...Steve

Ok. I think I get the idea. Thank you for the input

Regards,

-- 
Kristian Pedersen

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