Layer 3 health checks utilize ICMP-based echo requests (pings) to test whether a Real Server can be reached over the network. A Layer 3 check is not Virtual Service specific. For example - when it fails the corresponding Real Server may be removed from all Virtual Services that use it due to a routing issue. If ping fails due to routing – no higher-level health check should pass until the routing issue is resolved.

In contrast to the Layer 3 health checks, service based health checking for both the Layer 4 and Layer 7 health checks are Virtual Service based. When a Real Server fails such a check, it is removed only from the corresponding Virtual Service – all other Virtual Services that use this Real Server are unaffected, as long as their health check passes.