Hello there,
We spoke over gtalk, so I am going to summarize here.
the /etc/resolv.conf in your ubuntu box get modified by the OS, and you tried to stop that and didn't work.
That is not a Vagrant or Virtualbox issue, it's a feature in the OS.
I did send to you a Vagrantfile for Oracle linux 6.5, you can change to use centos
I did test it, and it's what I use for my test case, and PEERDNS=no in /etc/sysconfig/network-scripts/ifcfg-eth0 stop that
So, give it a try, test it.. you will see it works.
You can install the epel rpm in that vm and use puppet for your test.
something like
Feel free to email me if you have issues (mailme directly if you will write in other language rather than english please :) )
Alvaro.