check_by_ssh + firewall



I´m new in the forum and I´m a newbie in nagios too.
My problem is, that I have to control the server of our customers. So I want to use check_by_ssh. I have set up an authorized key in the firewall before the server our customers. Now I can cotrol the firewall but not the servers behind this one.

My question is, what shall I do, that I can control the servers. I think I want only unlock the port 22 for SSH. So I can get into the network of our customers. But I´m unsafely.

Have you any idea??

Thanks ludacris

PS.: My english is not so good…