title: No route to host. Github (composer) on ubuntu
body: <p>I'm trying to load a couple of dependencies with composer. Composer fails on a github repo. 
  I also cannot browse to <a href="http://github.com" rel="nofollow">http://github.com</a> and I can't reach github by ip. DNS seems fine since i can resolve github.com with nslookup. </p>
  
  <p>Any suggestions? </p>
  
  <p>`$ composer install
      Loading composer repositories with package information
      Installing dependencies (including require-dev)
        - Installing symfony/routing (v2.5.2)
          Downloading: 100%<br>
          Downloading: 100%<br>
          Downloading: 100%<br>
      Failed to download symfony/routing from dist: The "<a href="https://api.github.com/repos/symfony/Routing/zipball/24d5f003a794894513d67c888181ba8c3b8e0693" rel="nofollow">https://api.github.com/repos/symfony/Routing/zipball/24d5f003a794894513d67c888181ba8c3b8e0693</a>" file could not be downloaded: failed to open stream: No route to host
      Now trying to download from source
        - Installing symfony/routing (v2.5.2)
          Cloning 24d5f003a794894513d67c888181ba8c3b8e0693</p>
  
  <pre><code>  [RuntimeException]                                                          
    Failed to clone git@github.com:symfony/Routing.git via git, https, ssh pro  
    tocols, aborting.                                                           
    - git://github.com/symfony/Routing.git                                      
      fatal: unable to connect to github.com:                                   
      github.com[0: 192.30.252.129]: errno=No route to host                     
  
    - https://github.com/symfony/Routing.git                                    
      error: Failed connect to github.com:443; No route to host while accessin  
    g https://github.com/symfony/Routing.git/info/refs                          
      fatal: HTTP request failed                                                
    - git@github.com:symfony/Routing.git                                        
      ssh: connect to host github.com port 22: No route to host                 
      fatal: The remote end hung up unexpectedly                                
  
  
  
  install [--prefer-source] [--prefer-dist] [--dry-run] [--dev] [--no-dev] [--no-plugins] [--no-custom-installers] [--no-scripts] [--no-progress] [-v|vv|vvv|--verbose] [-o|--optimize-autoloader] [packages1] ... [packagesN]
  </code></pre>
  
  <p>`</p>