ssh/scp是很常用的命令，发现对有些主机， ssh建立连接速度特别慢，连接建立之后执行操作速度却很正常。

用 ssh -v 来查看详细的连接建立过程:

debug1: Authentications that can continue: publickey,gssapi-with-mic,password
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure. Minor code may provide more information
No credentials cache found

debug1: Unspecified GSS failure. Minor code may provide more information
No credentials cache found

debug1: Unspecified GSS failure. Minor code may provide more information

debug1: Next authentication method: publickey

原来是尝试 gssapi-with-mic 认证方式浪费了时间，打开 /etc/ssh/ssh_config 把里面的 GSSAPIAuthentication yes 改成 no 关掉它问题即解决。