Hi,   Network flows yes good question 🙂 Hosts file is a good question also !! 🙂  I terminated instances and created new one because i had some problems with cluster (i deleted hosts, and cluster). You talked about network, so for that with my new instances, i enabled all TCP's and ICMP's (before only ports indicated in documentation were opened : 7180,7183,7432, ICMP, SSH, HTTP,HTTPS) for the moment, i disabled IPv6 and changed hostname file with my private DNS instead of my IP adresse for each machine. I subscribed private IP's and their private DNS's in hosts file.   For info : I created new vpc (amazon) with public subnet and attached that to my instances. I let public IP only for SSH   Sure !! problem of network !!   Now Cloudera is installed in 4 nodes. inspector display good health. My heart is also in good health now. My head also 🙂 🙂   Please find below actions done, maybe another person can have the same problem :   - Edit Hostname in sudo nano /etc/hostname(Ubuntu) and for RHEL sudo nano /etc/sysconfig/network by replacing IP address with private DNS. - Edit hosts in sudo nano /etc/hosts for both Ubuntu and RHEL by adding Private IP addresses of  number of  Instances that you choose. If u choose 3 instances, enter the IP addresses of all the 3 Private IP’s and Private DNS’s but not the Public IP Address. The public IP  or Hostname is only for connecting with SSH to the remote and for making WINSCP connection. - Disable IPV6 by adding the following lines in sudo nano /etc/sysctl. conf # disable ipv6 net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1 net.ipv6.conf.lo.disable_ipv6 = 1 And issue the following command in order to make sure that it should contain 1 (after reboor) cat /proc/sys/net/ipv6/conf/all/disable_ipv6   Thank you a lot for your help. Sure i will come back with other questions 🙂   Could you please tell me what sould i activate as ports for security  ? This part is managed in AWS.   Best regards, Adil   ... View more