Excluding a range from a subnet

[Glenn Satchell]

That is correct. A fixed-address that happens to be in a dynamic range
could get allocated dynamically if the ping-before-offer doesn't get a
response. reserved leases and host statements require that you know the
mac address of the client.

The tidy way to do this is to migrate the fixed addresses so that they
are not scattered through the subnet. This may not be possible of
course.

Otherwise you will need to do multiple range statements for each subnet.

regards,
-glenn

>Subject: RE: Excluding a range from a subnet 
>Date: Wed, 23 Apr 2008 09:26:20 -0400
>From: "Randall C Grimshaw" <rgrimsha at syr.edu>
>
>That is how I understand it.
>I will recommend that you build some form of IP management database, and then 
essentially build the dhcpd.conf file from that. A database will help you track 
the reserved addresses over time.
>
>Randy
>
>-----Original Message-----
>From: dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org] On Behalf Of 
Olivier Bax de Keating
>Sent: Wednesday, April 23, 2008 9:02 AM
>To: dhcp-users at isc.org
>Subject: RE: Excluding a range from a subnet 
>
>Just to be sure,
>
>If I declare a host, with an ip and a mac address, the ip won't be reserved, 
that means, if in a subnet I declare a range containing that ip, it may be 
attributed dynamically? I would have to segment my ranges as in your example to 
be sure that my server won't propose this "reserved ip".
>
>Thanks for all
>
>Olivier
>
>-----Message d'origine-----
>De : dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org] De la part de 
John Hascall
>Envoyé : mercredi 23 avril 2008 13:35
>À : dhcp-users at isc.org
>Objet : Re: Excluding a range from a subnet 
>
>
>> I have to add a dhcp server in an already configured subnet, and manage
>> a range. The problem is that in my range, there may be one or many
>> devices with a static ip not configured in dhcp, and my dhcp server
>> musn't manage them. I'd like to declare one range, with excluded
>> ip/ranges to ignore. I had a look on internet but didn't find smthg
>> corresponding exactly to what I need :
>
>[manually abandon the addresses in the lease file]
>
>  This will surely bite you some day in the future.
>
>
>> Segmenting my range :
>
>   This is what you need to do.
>   It is not that hard or inelegant.  For example:
>
>	shared-network "sample" {
>		subnet 192.168.117.0 netmask 255.255.255.0 {
>			option broadcast-address 192.168.117.255;
>			option routers 192.168.117.254;
>			...
>		}
>		# we always reserve 0, 250-255
>		# 15, 42-49, 51-56, 61 are not managed by dhcp
>		pool {
>			range 192.168.117.1 192.168.117.14;
>			range 192.168.117.16 192.168.117.41;
>			range 192.168.117.50;
>			range 192.168.117.57 192.168.117.60;
>			range 192.168.117.62 192.168.117.249;
>			...
>		}
>	}
>
>
>> Declaring them as hosts :
>
>   Given a new enough version of dhcpd you can apparently 'reserve'
>   the in use addresses in th erange to the existing devices.  I
>   have not tried this myself.
>
>
>John
>
>
>
>