Static leases

Simon Hobson dhcp1 at
Wed Jul 20 07:07:45 UTC 2016

Graham Clinch <g.clinch at> wrote:

>> An automatic lease comes from an assigned range of addresses on a subnet
>> after matching either the defined host statement to the client
>> identifier or the hardware address. It's granted an infinite lease.
> I'm not sure about the phrase 'automatic lease' - are you referring to reserved leases through enabling the infinite-is-reserved configuration option?

Indeed, there seems to be an issue of terminology here. AIUI there are three types of lease :

Dynamic - allocated from a pool of addresses according to whatever policies/rules may be in place (eg "known" host, member of class, etc)
Reserved - Identical to the above, but flagged as reserved and so the address cannot be re-allocated to another client after expiry of the lease
Static - a fixed-address statement within a host declaration assigning a fixed static address.

A static lease doesn't go through the normal lease processes - so it's not recorded in the leases file, there's no "expiry" as far as the server is concerned. The server just gives out the lease and that's the end of it until the client comes back to renew. As a side effect, dynamic DNS updates don't happen with static leases - though there's an option which will put DNS entries in when the lease is issued, but no mechanism to remove them later.

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