Unfortunately I'm not on IRC yet, I'm actually an intern who just started work again last week so I'm still kind of getting my bearings. Plus it takes me a bit to figure out good answers to your questions anyway, so thank you for being patient with me. :)

In terms of how I installed facter, I just have my clone of the repository and I'm using bundler and rvm. I'm also using the hub gem in order to check out your pull request. Maybe this will help:

```
$ hub checkout https://github.com/puppetlabs/facter/pull/423
Branch razic-fix/2.x/17710_ipmodule_refactor set up to track remote branch fix/2.x/17710_ipmodule_refactor from razic.
Switched to and reset branch 'razic-fix/2.x/17710_ipmodule_refactor'
$ ruby --version
ruby 1.9.3p194 (2012-04-20 revision 35410) [x86_64-darwin12.3.0]
$ bundle --version
Bundler version 1.3.5
$ git log --oneline -1   
fe71d7b (#17710) Refactor the IP module
$ bundle install 
Resolving dependencies...
Using rake (10.0.4) 
Using coderay (1.0.9) 
Using diff-lcs (1.1.3) 
Using facter (1.7.0) from source at . 
Using json (1.7.7) 
Using metaclass (0.0.1) 
Using method_source (0.8.1) 
Using mocha (0.10.5) 
Using slop (3.4.4) 
Using pry (0.9.12.1) 
Using rspec-core (2.11.1) 
Using rspec-expectations (2.11.3) 
Using rspec-mocks (2.11.3) 
Using rspec (2.11.0) 
Using rspec-puppet (0.1.6) 
Using puppetlabs_spec_helper (0.4.1) 
Using redcarpet (2.2.2) 
Using watchr (0.7) 
Using yard (0.8.6.1) 
Using bundler (1.3.5) 
Your bundle is complete!
Use `bundle show [gemname]` to see where a bundled gem is installed.
$ FACTER_kernel=foo bundle exec facter                      
Error: undefined method `interfaces' for nil:NilClass
```