Easiest way would be to quickly open the core-site.xml file under HADOOP_HOME/conf directory. The value of fs.default.name property will tell you the host and port where NN is running.
Delete the line 127.0.0.1 localhost in your /etc/host and put your IP and the name of all your machines. Hadoop is resolving all the IPs and names of machines on the cluster as 127.0.0.1 localhost if you leave the file as default.