randomly(!) assign ip's from dynamic address range

[dave c]

To the best of my understanding, no.

The system is doing exactly what it was designed to do. It's running a 2hr lease (per your 
config). At the end of the 2hrs, if the device is not online anymore, it marks the lease as 
expired and that IP as available for another customer. It does record who was last assigned to 
it IIRC.

Later, 10hr later as per your example, a client comes back and requests an IP and is assigned a 
vacant IP, which happens to be the same IP that was most recently assigned to that MAC address.

This is actually a good thing as there are several operating systems which will stubbornly cling 
to the last IP they knew about even after lease expiration time. They don't behave well and can 
get themselves into quite a state, sometimes refusing to believe that the IP is no longer 
available.

If the prior IP wasn't available, the system would look for the oldest expired lease and assign 
that one to the client.

Basically, it won't start recycling IPs until enough new MAC addresses are seen to use up enough 
of the available unused IPs that the former customer's lease had already been assigned elsewhere.

Dave

On 6/5/15 08:10, Arne Baeumler wrote:
> Hi dhcp users,
>
> we are running a DHCP Server for about 10k customers with a single isc dhcpd (4.2.4p2) process running.
> Our customers do almost ever get the same IP Address assigned when sending DHCPDISCOVER.
>
> Lease time is 1200 sec. (20 minutes), pool is 95-97% in use all day. Even after 10h offline,
> dhcpd will answer an DHCPDISCOVER with an DHCPOFFER for the same ip address as assigned 10h earlier.
>
> Some of our customers would like their ip address to change from time to time (e.g. every 24h)
> as they where used to when using PPP.
>
> Is there any way to accomplish this using isc dhcpd?
>
>
>
> _______________________________________________
> dhcp-users mailing list
> dhcp-users at lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users
>

-- 
Dave Calafrancesco