Linux 使用SSH访问失败
用SSH访问Linux出现以下错误：
The host '192.168.15.249' is unreachable.
the host may be down,or there may be a problem with the network connection.Sometimes such problems can also be caused by a misconfigured firewall
原因是没有启动sshd服务
启动服务就可以正常访问。
service sshd start
