Option 82 or subnet: who wins?
Simon Hobson
dhcp1 at thehobsons.co.uk
Sat Mar 14 16:37:38 UTC 2009
David McGaughey wrote:
>Guess that I am confused about what "global" means for a class. If
>it means all class definitions are global, then by definition, it
>should not matter in what other context they are defined.
It's "a bit complicated" !
Whilst various constructs are 'global' in as much as (say) a host
statement defined anywhere will be available anywhere else, that's
not to say that locality of definition is irrelevant. I assume
classes are the same, but certainly for host statements, they are
available anywhere but can inherit properties from where they are
defined. For example, if you define a host inside one subnet
definition, but that host is booting from a different subnet, then it
will inherit some properties from the subnet where the host statement
is defined and some from where it's current lease derives from - the
result can be a host that gets given a router option for the wrong
subnet !
That's why the standard advice is to always define such things in the
global scope - if you don't then "interesting" things can happen.
And no I don't know why things are how they are - I'm sure parsers
are non-trivial to implement.
--
Simon Hobson
Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
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