Can I connect Zabbix server if I don't have client's IP , to be more specific I don't have any information about client except for information that I'm going to put in Zabbix agent config file like some name.
For example: I have several hosts in several different local networks and I want to get some information from them, but I don't know the IP address of host or router and I can't setup port forwarding on router, I just want to setup agent to be able to connect server over the internet that's all. Is that even possible?
Yes, use the active agent items only. Set the Zabbix server IP address in the ServerActive parameter and make sure the agent hostname matches the host name in the server (not the IP, not the DNS name).