I tried to access to my sever , but it refuse connection.
Can you help me to resolve this problem?

below there is the debug:

larzillo@Luigi-Notebook:~$ ssh -v root@172.18.2.254
OpenSSH_7.6p1 Ubuntu-4ubuntu0.3, OpenSSL 1.0.2n 7 Dec 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to 172.18.2.254 [172.18.2.254] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/larzillo/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/larzillo/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/larzillo/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/larzillo/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/larzillo/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/larzillo/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/larzillo/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/larzillo/.ssh/id_ed25519-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.3
ssh_exchange_identification: Connection closed by remote host

You've not supplied a password...or your server is not configured to allow root to ssh (as it should be)

Try with another user.

Wonder if Centos allows root ssh. For some reason I thought one had to use a lower level user and then use sudo or such????

Edit. Dohh. I just echoed scasey's post didn't I?

Yes, I have not installed version 8 yet but typically CentOS does enable ssh root login by default.

Could be due to several reasons. We don't have enough information as to if the OP changed anything from default.

The firewall although by default should allow ssh traffic on port 22.
hosts.deny or hosts.allow but by default should not be a factor.
Maybe a corrupted host key. Deleting ./ssh/known_hosts file may fix it. If you have more then one key in the file you might want to copy it although all it would do is ask to accept the key time you log into another server.

Hello,

Above output shows there is a problem with ssh_exchange_identification. It tries to read public key from another machine and it is not getting that public key. If you have access to another system try to execute below command:

# ls /etc/ssh/*

Output must show some key files. If file are present then we need to troubleshoot further or else we can try for reinstalling ssh package.

Awaiting for your response!!!

Have a nice day!!!

Thank you.
Diksha