Leases for fixed-address hosts not written to lease file?

[Glenn Satchell]

>Date: Wed, 23 May 2007 08:41:18 -0400
>From: "Steve van der Burg" <steve.vanderburg at lhsc.on.ca>
>To: <dhcp-users at isc.org>
>Subject: Re: Leases for fixed-address hosts not written to lease file?
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>>>> Simon Hobson wrote:
>> Steve van der Burg wrote:
>> 
>>>Using dhcpd-3.0.4, I can't seem to figure out why a lease given to a 
>>>host with configuration like this (pushed to the server via omshell)
>>>
>>>   host 00-19-bb-d7-8a-c2 {
>>>     dynamic;
>>>     hardware ethernet 00:19:bb:d7:8a:c2;
>>>     fixed-address 10.136.76.224;
>>>   }
>>>
>>>doesn't show up in the leases file.  I can see that the lease is 
>>>fine (by checking what the client gets), and all of my "normal" (ie. 
>>>no fixed address, just regular dynamic address assignment) leases 
>>>are logged just fine.
>>>
>>>Any ideas?
>> 
>> Yes
>> 
>> The server does not write lease records for such leases - on the 
>> basis that it doesn't need to, all the information it needs is in the 
>> config file.
>
>After sending my original message to the list, yesterday, I discovered an 
earlier reference to the same question here: 
http://groups.google.ca/group/lucky.freebsd.questions/browse_thread/thread/5c736
794694d1003/69d6fb31c584e907?lnk=st&q=isc+dhcpd+not+recording+fixed+address+leas
es&rnum=1&hl=en#69d6fb31c584e907
>
>There's a patch referenced in that message to get the fixed-address
>leases written out to another file, but now I can't find that
>anywhere.  If someone could just point me to the approximate spot in
>the source where I'd need to hack something similar in, it would likely
>save me a bit of work unwinding what's already in there.

If you can use version 3.1.0 then there is a new facility called
Reserved Leases which behaves more like a normal lease. That way you
get the constant IP address behaviour and the normal lease file
entries. A search of the archives should give somemore background.

This is from the 3.1.0a3 dhcpd.conf man page.

RESERVED LEASES
     It's often useful to allocate a single address to  a  single
     client,  in  approximate  perpetuity.   Host statements with
     fixed-address clauses exist to a  certain  extent  to  serve
     this  purpose,  but  because host statements are intended to
     approximate 'static configuration',  they  suffer  from  not
     being referenced in a littany of other Server Services, such
     as dynamic DNS, failover, 'on events' and so forth.

     If a standard dynamic lease, as from any range statement, is
     marked  'reserved',  then the server will only allocate this
     lease to the client it is identified by (be that  by  client
     identifier or hardware address).

     In practice, this means that the lease  follows  the  normal
     state  engine,  enters ACTIVE state when the client is bound
     to it, expires, or is released, and any events  or  services
     that would normally be supplied during these events are pro-
     cessed normally, as with any other dynamic lease.  The  only
     difference is that failover servers treat reserved leases as
     special when they enter the FREE or  BACKUP  states  -  each
     server applies the lease into the state it may allocate from
     - and the leases are not placed on the queue for  allocation
     to  other  clients.   Instead  they  may  only be 'found' by
     client identity.  The result  is  that  the  lease  is  only
     offered to the returning client.

     Care should probably be taken to ensure that the client only
     has  one  lease  within a given subnet that it is identified
     by.

     Leases may  be  set  'reserved'  either  through  OMAPI,  or
     through  the 'infinite-is-reserved' configuration option (if
     this is  applicable  to  your  environment  and  mixture  of
     clients).

     It should also be noted that leases  marked  'reserved'  are
     effectively treated the same as leases marked 'bootp'.

regards,
-glenn