Query

[Gregory Sloop]

There have been quite a few queries on this list over the years asking essentially the same question you ask.
 
As I recall, there's any (easy) way to get ISC DHCPd to do this.
 
And for good reason - it's not in agreement with RFC's for DHCPd. ...Namely that clients should get the same IP back at renewal, and after expiration, the server should try to assign IP's in the following order;
1) IP's that have never been assigned
2) Reuse of least recently used to most recently used.
 
Forcing expiration of the lease without good cause it really bad practice. Any open sessions, when the ip is forced to expire and a new ip assigned will (generally) be abruptly terminated. This is not desirable.
 
IIRC, there's lots of other detail around the question - as well as some discussion about how to "force" the behavior you seek (even if ill advised.)
Might I suggest that you search the list and see if you can dig up those threads. 
 
They'd be useful (hopefully) in dissuading you from doing what you want to do, or in the case it doesn't, help you know how you might accomplish this, IMO, misguided task. :)
 
 
 

> Hi everyone,
> I m working for a small company that sells the Internet as an ISP.  One of our clients calls every day about its IP address that is always the same. Even though the client is on a dynamic pool, I think, when the router automatically attempts to renew as soon as 50 percent of the lease duration has expired, the DHCP server allocated the same IP.
> Is there a command configuration in which I say change the IP address no matter what? I mean, when the DHCP client tries to renew the IP address.
> thank you for your time.
> Best,
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