The situation is: when connect to a server with SSH session, it starts up slowly (but the web connection is fast). For some tracing and debugging, it is due to the stupid DNS setting by someone.
The reference is – SSH session slow to start? It’s the DNS stupid!, and the solution listing:
1. Check for the DNS settings in /etc/resolv.conf or NetworkManger in Gnome or any management tools on desktop environment. Or
2. Set the ”UseDNS no” in sshd config: /etc/ssh/sshd_config, and then restart sshd.
Enjoy it. 🙂