Leases for fixed-address hosts not written to lease file?
Glenn Satchell
Glenn.Satchell at uniq.com.au
Wed May 23 12:59:54 UTC 2007
>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
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