The Cisco Open NX-API REST interface, described in the previous section, is a very powerful interface for pushing configuration changes or pulling information from the Cisco Nexus switches. However, there might be instances where it might be desirable to receive notifications from the switch directly- for example, when a counter representing unexpected packet errors increments.

Cisco Open NX-OS provides an interface capability to enable the switch to push notifications to interested subscribers. Through the NX-API WebSocket interface, programs and end-users can receive notifications about various state changes on the switch, eliminating the need for periodic polling. The interface establishes full-duplex communication on a single session with a remote entity.