http://isc-dhcp-users.193.s1.nabble.com/randomly-assign-ip-s-from-dynamic-address-range-tp156p183.html
Most dhcp clients also store the last address. So even if you configure
> A Windows 8 client appears to keep the last IP in the registry in:
> HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{...<Network
> Adapter>...}\DhcpIPAddress
>
> Although many years ago I remember having clients that remembered the last
> 5 or 10 IP's (in different subnets).
>
>
>
> --
> Bob Harold
> hostmaster, UMnet, ITcom
> Information and Technology Services (ITS)
>
[hidden email]
> 734-647-6524 desk
>
> On Mon, Jun 8, 2015 at 9:11 AM, Glenn Satchell
> <
[hidden email]>
> wrote:
>
>>
>> On Mon, June 8, 2015 7:29 pm, Arne Baeumler wrote:
>> > Hi Simon,
>> >
>> > thank you for your reply.
>> >
>> > On 2015-06-05 15:05, Simon Hobson wrote:
>> >> Hmm, that's a variation I don't think we've seen before ;-)
>> >> What you are seeing is correct operation according to the RFCs - the
>> >> server is required to keep the address stable as far as is possible,
>> and
>> >> that means the client can come back after an arbitrary length of time
>> >> and as long as the address has not been re-used then the client
>> *must*
>> >> get the same address.
>> >
>> > Would you please point me to the RFC you are referring to?
>> > Can't find any requirements for the server to maintain some kind of IP
>> > history in RFC2131.
>> >
>>
>> I'm looking at
https://www.ietf.org/rfc/rfc2131.txt, there are several
>> references to this feature within the document. Section 4.3.1 is the
>> clearest on this, even though it says it "SHOULD" rather than "MUST" be
>> done this way.
>>
>> 1.6 Design goals
>>
>> o Retain DHCP client configuration across DHCP client reboot. A
>> DHCP client should, whenever possible, be assigned the same
>> configuration parameters (e.g., network address) in response
>> to each request,
>>
>> o Retain DHCP client configuration across server reboots, and,
>> whenever possible, a DHCP client should be assigned the same
>> configuration parameters despite restarts of the DHCP mechanism,
>>
>> 2.2 Dynamic allocation of network addresses
>>
>> The
>> allocation mechanism (the collection of DHCP servers) guarantees not
>> to reallocate that address within the requested time and attempts to
>> return the same network address each time the client requests an
>> address.
>>
>> 4.3.1 DHCPDISCOVER message
>>
>> When a server receives a DHCPDISCOVER message from a client, the
>> server chooses a network address for the requesting client. If no
>> address is available, the server may choose to report the problem to
>> the system administrator. If an address is available, the new address
>> SHOULD be chosen as follows:
>>
>> o The client's current address as recorded in the client's current
>> binding, ELSE
>>
>> o The client's previous address as recorded in the client's (now
>> expired or released) binding, if that address is in the server's
>> pool of available addresses and not already allocated, ELSE
>>
>> o The address requested in the 'Requested IP Address' option, if
>> that
>> address is valid and not already allocated, ELSE
>>
>> o A new address allocated from the server's pool of available
>> addresses; the address is selected based on the subnet from
>> which
>> the message was received (if 'giaddr' is 0) or on the address of
>> the relay agent that forwarded the message ('giaddr' when not
>> 0).
>>
>> I hope this helps.
>>
>> I realise this doesn't help with your original question :) In terms of
>> privacy there is an IPV6 feature that assigns a new IP address each day.
>> This is part of the client functionality defined in RFC 4941 "Privacy
>> Extensions for Stateless Address Autoconfiguration in IPv6" but doesn't
>> help with your current IPv4 issue.
>>
>> regards,
>> -glenn
>>
>>
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