ddns updates for reserved (fixed-address) IPs

Simon Hobson dhcp1 at thehobsons.co.uk
Fri Feb 7 16:47:02 UTC 2014

John Miller <johnmill at brandeis.edu> wrote:

> In my test system, it appears that if an address is part of a dynamic pool, its associated DNS records will be deleted when the IP is freed for use.


> With hosts configured using the 'fixed-address' parameter, however, associated DNS records do not appear to be deleted when the host in question has its lease expired.

They aren't added by default either. Host statements with a fixed address do not result in a lease being created, by default there is no DNS update, and because there is no lease to expire there will be no DNS removal at the end of the lease.

> ... if we expand a dynamic pool to include some previously reserved addresses, do we then need to manually clean up DNS to remove the old fixed-address A and TXT records?


However, current versions now support a "reserved" status for a lease. The only way to set it is to add the reserved keyword to a lease - either by editing the leases file (or using OMAPI ?). But once set, the lease then behaves as any other lease (DDNS updates, lease expiry etc) apart from being tied to a specific client.
For some uses, this may be more appropriate than host statements.

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