I am using OpManager v12.2. When adding a Linux device to monitor with CLI credentials, I find that disk, cpu and memory utilisation monitoring is only available if the CLI credentials are set to use telnet protocol only. With SSH, I just get basic ICMP information only(availability, packet loss, response time). I have enabled both SSH protocols v1 and v2 on the Linux device but it makes no difference. 

Obviously, I would not want to use telnet if it all possible. How can I fix this?

Thanks.