Override dynamic lease with static reservation

[Christian Kratzer]

Hi Marc,

On Fri, 27 Sep 2019, Marc Haber wrote:

> Hi,
>
> I find it a rather common occurence that a client that currently holds a
> dynamic lease should get a static reservation of a different IP address.
> Thus, a host entry is put into the configuration and the client
> rebooted.
>
> It then asks for the last IP address it knows of, which is the dynamic
> address. The server proceeds to look in its database, says "yup, here is
> the address".
>
> The usual method is to delete the dynamic address from the database,
> which either involves a rather fragile and often misbehaving omshell
> process where the only "documentation" is half a mailing list thread
> from ten years ago, or shutting down the server and hand-editing the
> database file (which is a service interruption).
>
> Is there a configuration option to tell the server "if there is
> something static for this client, forget everything dynamic you might
> have and NAK the dynami address from the client"?

my experience with isc dhcp is that once you have a host reservation
that matches the client, the host reservation takes precedence over
any historic lease.

This should automatically lead to the server sending a NAK to a client
requesting the old dynamic lease.

If it is not sending a nack then I would think that your host
reservation is not matching the client request. Subnet mismatch or
criteria mismatch.

So you can just leave the lease to expire normally.

Greetings
Christian

-- 
Christian Kratzer                   CK Software GmbH
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