I'm wondering what are best practices for overriding variables in puppet. I'd like to have all my nodes (which located in different places, some of them are qa, some live) with same classes. Now I have something like this:

class base_linux {
   <...> # something which requires $env and $relayhost variables
}

class linux_live {
   $relayhost="1.1.1.1"
   $env = "prod"

   include base_linux
}

class linux_qa {
   $relayhost="2.2.2.2" # override relayhost

   include base_linux
}

class linux_trunk {
   $env = "trunk" # override env

   inlude linux_qa
}

node "trunk01" {
   include linux_trunk
   include <something else>
}
node "trunk02" {
   $relayhost = "3.3.3.3" # override relayhost
   include linux_trunk
   include <something else>
}

node "prod01" {
   include linux_prod
}

So, I'd like to have some defaults in base_linux, which can be overrided by linux_qa/linux_live, which can be overrided in higher level classes and node definition.

Of course, it does not work (and not expected to work). It does not work with class inheritance as well. Probably, I'll be able to archive using global scope variables, but it does not seems like a good idea to me.

What is the best way to solve this problem?