[Dnsmasq-discuss] DNS from dhcp-host while client is offline

Simon Kelley simon at thekelleys.org.uk
Thu Oct 7 21:15:28 UTC 2021

On 04/10/2021 13:37, Dominik Derigs wrote:

> Initially, I've myself found this an odd behavior to only serve
> only DHCP host names that are known to be "alive". I do see some
> value in not serving A records when we know the server is
> offline, however, the very same happens on the Internet all the
> time: no DNS server I'm aware of checks if an A record is
> reachable before giving you the reply.

The reason it works that way is that it allows a DHCP client to be
associated with multiple addresses for when it may appear on different
subnets at different times. The address that goes "live" in the DNS is
not just the address that the client has a lease for, but the address of
the last lease it obtained, so that it's address can be determined as it
moves between subnets.


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