This read-write object indicates whether this networking entity is currently operating as an intermediate system, forwarding CLNP packets on behalf of others, or as an end system that only sends and receives its own traffic. An admin sets this to control whether a device acts as an OSI-network-layer router versus a pure host, since only an entity configured as IS will forward PDUs that are not addressed to itself. For example, switching this from es(2) to is(1) on a device would turn it into a CLNP-forwarding router rather than a simple end host that drops any transit traffic.