## Dependencies Icinga 2 uses host and service [Dependency](#objecttype-dependency) objects either directly defined or as inline definition as `dependencies` dictionary. The `parent_host` and `parent_service` attributes are mandatory, `child_host` and `child_service` attributes are obsolete within inline definitions in an existing service object or service inline definition. A service can depend on a host, and vice versa. A service has an implicit dependency (parent) to its host. A host to host dependency acts implicit as host parent relation. When dependencies are calculated, not only the immediate parent is taken into account but all parents are inherited. A common scenario is the Icinga 2 server behind a router. Checking internet access by pinging the Google DNS server `google-dns` is a common method, but will fail in case the `dsl-router` host is down. Therefore the example below defines a host dependency which acts implicit as parent relation too. Furthermore the host may be reachable but ping probes are dropped by the router's firewall. In case the `dsl-router``ping4` service check fails, all further checks for the `ping4` service on host `google-dns` service should be suppressed. This is achieved by setting the `disable_checks` attribute to `true`. object Host "dsl-router" { macros.address = "192.168.1.1" } object Host "google-dns" { macros.address = "8.8.8.8" } apply Service "ping4" { import "generic-service" check_command = "ping4" assign where host.macros.address } apply Dependency "internet" { parent_host = "dsl-router" disable_checks = true assign where host.name != "dsl-router" }