stuck up record in DNS

Simon Hobson dhcp1 at
Sun Aug 11 20:10:45 UTC 2019

Nepryakhin Ivan <nepryakhin at> wrote:

> I'm encountered with a strange issue:

See below - it's "correct" operation for your example

> cuted of the file dhcpd.conf:
> ## DDNS related configuration
> ddns-update-style interim;
> ddns-rev-domainname "";
> ddns-domainname "tsc.";
> update-static-leases on;
> group {
>         option routers;
>         ddns-hostname = host-decl-name;
>         update-optimization false;
>         update-conflict-detection false;
> # example host 
>             host host12 {
>                 hardware ethernet 18:31:BF:xx:xx:xx;
>                 fixed-address;
>         }
> }

Where you have a host entry, the lease does NOT go through the normal lifecycle - and would not normally appear in the leases file.
Without the "update-static-leases on" statement, there would be no DNS update at all. With it, the DNS will be updated every time the host is leased that address - but those DNS records are never removed. Normally, the admin would be expected to add their own DNS entries to match host entries - the "update-static-leases on" statement is really just to save work.

If you want a "fixed" address for a host, and you want the DNS to be added/removed as required, then there is one option available. Add the "reserved" flag to a lease for the host - this fixed the lease so that it will not be allocated to another host. The lease is in all other respects the same as any dynamic lease.

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