I have a bunch of OpenStack instances which think their IP address is 1.100.x.y, but their public IP range (which Zabbix would use to communicate with them) is 100.100.x.y. So for instance, an instance that I want to monitor, in ifconfig, shows its own IP address as 1.100.10.24. Its public IP address - used for all connectivity in & out - is 100.100.3.9. I've set up auto-registration, but these hosts register themselves (successfully) with the Zabbix server using the 1.100.10.24 address. The server then cannot communicate with the agents because it's trying to connect to the private IP rather than the public. I tried overriding this by having the agent listen on the public IP (via the ListenIP config param), but of course this doesn't work because the agent can't listen on that address since the interface knows nothing about it. The net result is there appears to be no way to have autoregistration add these hosts. A seemingly simple solution would be to specify a public IP config param that gets sent during autoregistration.