Host Declaration

Simon Hobson dhcp1 at thehobsons.co.uk
Fri Sep 22 15:59:28 UTC 2017


Jérôme BECOT <jerome.becot at inalco.fr> wrote:

> I'm wondering about the difference between declaring hosts at the global level and in their respective subnets. It looks like the same to me but I may miss something about it.

The difference you've missed is that you get "interesting" inheritance problems !

Host statements are always global in scope regardless of where they are declared. However, as a quirk of implementation, they can inherit from where they are defined. The result of this is that you can have a client that gets an address from one subnet, but options like gateway from a different subnet - something that's obscure and hard to pin down.

In many cases you'll get away with it. If you define hosts with a single IP address, then they'll either use that host declaration in that subnet, or if in another subnet they won't use it. It's only when you define multiple addresses, or none at all, that the problem shows up.

TL;DR version :
Always put your hosts in the global scope - or in a group if you want to assign common options to multiple hosts.



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