ISC DHCPD giving out reserved IPs for non-reserved hosts

Glenn Satchell Glenn.Satchell at
Mon Jul 9 14:01:00 UTC 2007

>From: "Brent L. Bates" <blbates at>
>Date: Mon, 9 Jul 2007 09:54:40 -0400
>     Since when does Micro$loth do anything in the `standard' way.  I believe
>their DHCP server `reserves' IP addresses.  ISC's DHCPD server versions less
>than 3.1 create `fixed addresses'.  I know it is a subtle difference, but it
>is a difference.  Check the list archives for details.  I haven't used the new
>version of ISC's DHCPD server yet, so I don't remember the details on if the
>IP address ranges are set up differently for fixed addresses and reserved
>ones.  Someone else on the list will know better.

With MS dhcp server you say 'use these addresses, except for these few
I specify'.

With ISD dhcpd you say 'use this range of addresses'.

So, if you have some fixed addresses supplied using host statements then you 
need to make sure these addresses are not part of the dynamic range. It means 
you can end up with things like:

subnet ... {
host ... {


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