Static IP and IP management

Chuck Anderson cra at WPI.EDU
Wed Feb 24 18:44:40 UTC 2016

On Wed, Feb 24, 2016 at 01:17:13PM -0500, Bernard Fay wrote:
> When the dhcpd server assign a static IP to a device, it also instruct bind
> to add an entry in the DNS zone file.  One thing I realized is that if a
> device didn't renew his lease, the entry in the DNS zone file is not
> removed.  I would have thought to use the zone files to know if a device is
> in use or not.  I had in mind that the lease time would have help to know
> if a device therefore an IP is use or not.  In other words, a device
> requires an IP and the dhcpd server assigned it a statically defined IP
> address. The dhcpd server also instruct bind to add an entry in the
> appropriate zone file.  Eventually the device is turned off, the lease time
> reach its limit then I would have expected the dhcpd server to instruct
> bind to remove the entry regarding this device but it is not the case.
> Then I could have take a look at the zone files to know what is in used and
> I would know what is not in use.
> Either I made something in my configuration or I was expecting too much
> from dhcpd and bind.

You can do that, but you have to use "reserved" leases rather than
fixed-address statements.  ISC dhcpd doesn't track the expiry of
fixed-address leases.

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