Connection closed by 203.0.113.10 port 22

Common causes

• The server rejected the user or source address (AllowUsers, DenyUsers, fail2ban, hosts.deny).
• Authentication failed and the server dropped the session.
• sshd hit MaxStartups under load or a brute-force attempt and refused new sessions.

How to fix it

1. Run ssh -vvv user@host to see the last step before the close.
2. Check the server log (journalctl -u ssh or /var/log/auth.log) for the matching entry.
3. If you are banned by fail2ban, unban your IP: fail2ban-client set sshd unbanip <ip>.