ISC DHCPD giving out reserved IPs for non-reserved hosts

John Wobus jw354 at
Fri Jul 6 20:29:46 UTC 2007

It's possible you are seeing normal behavior.  If you are using host 
to attempt to reserve addresses, you are under a misimpression.  Host 
do not reserve addresses; they merely tell the server to give a certain
answer when they receive a certain MAC address.
You reserve addresses by leaving them out of the configured ranges
that are dynamically allocated.

John Wobus

On Jul 6, 2007, at 3:31 PM, Scott Lacy wrote:

> I have a DHCP server running ISC DHCPD v3.0.3 on Fedora Core.  I am
> having an issue where dhcpd is giving out leases for reserved IP
> addresses to hosts other than that which the addresses are reserved
> for.  There are no indication in the logs of any conflicts.  The logs
> look fairly vanilla and there was no indication of any trouble until I
> got a call about an IP conflict with the machine the reservation is
> for.  The only quick way to resolve the problem was to power down the
> offending device.  Even removing the newly-issued lease from DHCP and
> having the other device pull an address did not seem to help.
> Is there anything that jumps out to any of you as far as things I 
> should
> check my configuration for?  I've run this installation for almost a
> year and I've had this come up twice in the last month, both on 
> networks
> that were set up in DHCP long ago.
> Thanks,
> Scott Lacy
> Systems Manager
> Mercer University

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