现象
CentOS 7.6 安装Oracle 11.2.0.4 rac，静默安装grid集群软件报错：
[FATAL] [INS-06006] Passwordless SSH connectivity not set up between the following node(s): [oarac2].
CAUSE: Either passwordless SSH connectivity is not setup between specified node(s) or they are not reachable. Refer to the logs for more details.
ACTION: Refer to the logs for more details or contact Oracle Support Services.其它现象：
1、用以下命令已经配置过互信了，而且可以确定互信是配置成功的：
/soft/database/sshsetup/sshUserSetup.sh -user oracle -hosts "oarac1 oarac2" -advanced exverify –confirm
/soft/database/sshsetup/sshUserSetup.sh -user grid -hosts "oarac1 oarac2" -advanced exverify –confirm因为以下命令可以不输入密码就可以返回日期的：
ssh oracle@rac2 date
ssh grid@rac2 date
ssh oracle@rac1 date
ssh grid@rac1 date2、奇怪的地方是，用ssh互相连接的时候不能连接
ssh oracle@rac2
ssh oracle@rac2
ssh root@rac2
[root@oarac1 ~]# ssh root@oarac2
ssh: connect to host oarac2 port 22: Connection timed out
[oracle@oarac1 ~]$ ssh oracle@oarac2 -vvvv
OpenSSH_7.4p1, OpenSSL 1.0.2k-fips 26 Jan 2017
debug1: Reading configuration data /home/oracle/.ssh/config
debug1: /home/oracle/.ssh/config line 1: Applying options for *
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 58: Applying options for *
debug2: resolving "oarac2" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to oarac2 [172.20.7.82] port 22.
debug1: connect to address 172.20.7.82 port 22: Connection timed out
ssh: connect to host oarac2 port 22: Connection timed out防火墙和selinux都已关闭！！！
原因
华为云服务器的安全组拒绝了22端口：
解决
修改该安全组问题得到解决。
其它可能的原因
1、主机名不能大写，需要改为小写，请参考：https://blog.csdn.net/m0_37625564/article/details/115242416 和 MOS：11.2.0.4 runInstaller: [INS-06006] Passwordless SSH connectivity not set up between the following nodes(s) (Doc ID 1597212.1)
2、需要删除虚拟机自带的虚拟网卡virbr0
1、ifconfig virbr0 down
2、brctl delbr virbr0
3、systemctl disable libvirtd
4、重启虚拟机
5、将原来的rm -rf /home/grid/.ssh文件删除，重新Setup,Test即可3、若是AIX系统，则可以如下解决：
ln -s /usr/bin/ksh /bin/bash
mkdir -p /usr/local/bin
ln -s /usr/bin/ssh-keygen /usr/local/bin/ssh-keygen
ln -s /usr/bin/ssh /usr/local/bin/ssh
ln -s /usr/bin/scp /usr/local/bin/scp4、用户密码错误
5、环境变量配置错误
