inconsistent ddns behaviour

Simon Hobson dhcp1 at thehobsons.co.uk
Mon Mar 27 16:31:45 UTC 2017


Rick Dicaire <kritek at gmail.com> wrote:

> Are directives in each subnet declaration global in effect, or particular only to the subnet declaration? My expectation was they'd only apply to that subnet declaration, so I'm unclear.

In general they are local in scope - so you have global options, over-ridden by shared-subnet options, overridden by subnet options (there are also scopes for group and class but I'll leave them out for now).

BUT - some statements are global in scope wherever they are defined. Class and host declarations are in this list - but because of inheritance, you can get some really strange effects where (for example) you can have a class or host statement that matches a client, causing a client to inherit options from the subnet where the class or host is defined, even though the host is in another subnet altogether !
Hence you may have seen in the archives advice to never define hosts or classes anywhere but in the global scope.



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