dhcpd.leases question

[Glenn Satchell]

> On 06/06/2012 11:20 AM, Glenn Satchell wrote:
>>> On 06/05/2012 10:28 AM, Glenn Satchell wrote:
>>>> On 06/05/12 23:10, Glenn Satchell wrote:
>>>>> On 06/05/12 22:26, Nicolás Valera wrote:
>>>>>> Hi, sorry about my ignorance but, what does it means "rewind binding
>>>>>> state free;" in dhcpd.leses file?
>>>>>> Thanks in advance!
>>>>>> Nix.
>>>>> Hi Nicolás
>>>>>
>>>>> The dhcpd.leases man age describes the format of the leases file.
>>>>>
>>>>> binding state state; next binding state state;
>>>>>
>>>>> The binding state statement declares the lease's binding
>>>>> state. When the DHCP server is not configured to use the
>>>>> failover protocol, a lease's binding state will be either
>>>>> active or free. The failover protocol adds some additional
>>>>> transitional states, as well as the backup state, which
>>>>> indicates that the lease is available for allocation by the
>>>>> failover secondary.
>>>>>
>>>>> A binding state of "active" means there is a client using this
>>>>> particular lease now.
>>>>>
>>>>> A state of "free" means there is no client using this lease at the
>>>>> moment and it is available to be given out by the server.
>>>>>
>>>> Sorry about that - it would be helpful if I read the question a bit
>>>> more closely!
>>>>
>>>> Rewind binding state is used in failover. If the two servers go into
>>>> communications-interrupted mode where they lose contact with each
>>>> other, normally a particular server can only hand out new leases from
>>>> it's share of the free pool. The idea is to allow it to reset the
>>>> binding state of a lease so that it can re-issue the IP address. This
>>>> is a fairly complex optimisation of the failover conditions which
>>>> would not occur in normal operation and only rarely if failover
>>>> situations, so it is something you shouldn't worry about too much.
>>>>
>>> Thanks for the answer!
>>> but i'm not using the failover option, why my leases file contains
>>> that?
>>>
>>> Thanks again and sorry about my English!
>> This is a comment from the source code in server/failover.c
>>
>>           * In failover rules, a server is permitted to work forward in
>> certain
>>           * directions from a given lease's state; active leases may be
>>           * extended, so forth.  There is an 'optimization' in the
>> failover
>>           * draft that permits a server to 'rewind' any work they have
>> not
>>           * informed the peer.  Since we can't know if the peer received
>> our
>>           * update but was unable to acknowledge it, we make this change
>> on
>>           * transmit rather than upon receiving the acknowledgement.
>>
>> rewind_lease_state is mentioned in a few other source files. It seems to
>> be default behaviour to include it in the leases file, even when
>> failover
>> is not configured.
>>
>> regards,
>> -glenn
>
> Tanks a lot!
> the last one:
> can i remove from the leases file without any consequences and then move
> it to the new dhcp server?

Probably, but the new dhcp server will just write out the rewind line
again, so easier to just leave the file as is.

regards,
-glenn