Question : Flush the DHCP cache?

I am running a Windows 2003 network.  My issue is that I need to clear all of the IP leases out of DHCP.  I have our routers natted so that certain IP ranges take a certain path to the internet (different T1 carriers).  The problem with this is that there is no organization on how our IP addresses are leased out.  For instance, If I have an IP Address at #.#.#.115, when my IP lease expires, I will most likley be assigned the same number.  The way I want it to work is that DHCP assigns the lowest number IP address that is available.  

So what I basically need is two things:

1) to clear out the DHCP leases so that the next person who logs into my network gets assigned #.#.#.1.  
2) when someone's IP lease expires, DHCP assigns them the lowest availible IP, instead of giving them the same IP they had before.

Any help would be greatly appreciated.

Thank you
Roger Settle
[email protected]om

Answer : Flush the DHCP cache?

The problem here is that the lease won't expire while the machine is connected.

At half the lifetime of the lease the machine will send a request to extend the lease.  By RFC design the DHCP server is obligated to extend the lease again by the full lifetime of the lease.

Lease set to 1 day.
Machine gets IP address.
12 hours later the machine send a renewal request.
DHCP server extends ease by 1 day.
Machine disconnects.
DHCP server cannot give that IP to anyone else for 24 hours.

When the machine reconnects it send a renewal request for it's IP.
If it is withing the lifetime of the lease the DHCP server is again obligated to extend the lease by the full lifetime.

If it is past the lifetime and no other machine has been assigned that IP the DHCP server is obligated to start a new lease for that IP for the full lease lifetime.

If the IP address has already been leased to another machine the DHCP server responds with an error and the machine requests a new lease and willbe assigned the lowest available IP at that time.

The only way to do what you are wanting to do is to use a 3rd party DHCP server and I'm not sure there are any that will do what you wnat it to.

Dave Dietz