Fixed address inside dynamic range

Martin McCormick martin at
Tue Mar 6 20:44:25 UTC 2012

Simon Hobson writes:
> No
>     It would be a real pain to reconfigure all my networks (which have 
> lots
>     of hosts inside dynamic range)
> You reap the reward for an unplanned (not well managed ?) network.
>     Any thoughts?
> You may want to consider reserved leases. These act like normal leases, 
> but
> cannot be re-allocated to another client. So you get the benefit of having
> a "fixed" address for a client, but also the advantages of following the
> normal lease lifecycle (so DNS updates work for example).

	How long have reserved leases been available? In our
operation, we have been using first bootP then DHCP since the
mid nineties and the general rule of thumb has been to assign
about half the addresses in a given subnet/VLAN to dynamic dhcp
and leave the other half open to either bootP assignments or ip
assignments in DNS only without any DHCP involvement.

	We have been using omshell all be it driven by expect
scripts, to create and destroy bootP assignments. We have
somewhat over 8-thousand of these so stopping and restarting
dhcpd each time one of them needs to be changed is not really an
option any more. The only disadvantage I have seen to using
omshell to handle the static bootP entries is that one must
always make sure to run the same omshell commands on each DHCP
server or one will certainly assign a dynamic lease and the
other will assign the bootP address which is a very bad thing

Martin McCormick

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