title: Unable to connect to internal network from inside the container
body: <p>I have following Dockerfile:</p>
  
  <pre><code>FROM node:8
  WORKDIR /tmp
  COPY package.json /tmp/
  RUN npm config set registry http://xxx:8081/repository/npm-group/
  RUN npm install
  
  WORKDIR /opt/app
  COPY . /opt/app/
  RUN cp -a /tmp/node_modules /opt/app/
  
  EXPOSE 3000
  
  ENTRYPOINT [ "npm", "start" ]
  </code></pre>
  
  <p>When I try to build an image using:</p>
  
  <pre><code>docker build -t blah .
  </code></pre>
  
  <p>All goes well until I get to step 5/10, npm install. The logs show:</p>
  
  <pre><code>npm ERR! errno ETIMEDOUT
  npm ERR! network request to http://xxx:8081/repository/npm-group/prop-types failed, reason: connect ETIMEDOUT x.x.x.x:8081
  </code></pre>
  
  <p>I have no idea what is happening. The Nexus repository is hosted on the internal network, so I have no idea why it cannot be contacted.</p>
  
  <p>Iptables shows the following:</p>
  
  <pre><code>philippe@laptop:~/localdev/react-starterkit$ sudo iptables -L
  Chain INPUT (policy ACCEPT)
  target     prot opt source               destination         
  
  Chain FORWARD (policy ACCEPT)
  target     prot opt source               destination         
  DOCKER-USER  all  --  anywhere             anywhere            
  DOCKER-ISOLATION-STAGE-1  all  --  anywhere             anywhere            
  ACCEPT     all  --  anywhere             anywhere             ctstate  RELATED,ESTABLISHED
  DOCKER     all  --  anywhere             anywhere            
  ACCEPT     all  --  anywhere             anywhere            
  ACCEPT     all  --  anywhere             anywhere            
  
  Chain OUTPUT (policy ACCEPT)
  target     prot opt source               destination         
  
  Chain DOCKER (1 references)
  target     prot opt source               destination         
  
  Chain DOCKER-ISOLATION-STAGE-1 (1 references)
  target     prot opt source               destination         
  DOCKER-ISOLATION-STAGE-2  all  --  anywhere             anywhere            
  RETURN     all  --  anywhere             anywhere            
  
  Chain DOCKER-ISOLATION-STAGE-2 (1 references)
  target     prot opt source               destination         
  DROP       all  --  anywhere             anywhere            
  RETURN     all  --  anywhere             anywhere            
  
  Chain DOCKER-USER (1 references)
  target     prot opt source               destination         
  RETURN     all  --  anywhere             anywhere            
  </code></pre>
  
  <p>Any ideas?</p>