Egress statistics are supported for the three RIB-API tunnel tables (IPv4, IPv6, and MPLS). The counters are attached to the NHLFE of each next hop. Counters are effectively allocated by the system at the time that the instance is programmed in the data-path. Counters are maintained even if an instance is deprogrammed and values are not reset. This means that, if an instance is reprogrammed, traffic counting resumes at the point where it last stopped. Traffic counters are released and therefore traffic statistics are lost when the instance or entry is removed from the database.
No retry mechanism is available for egress statistics. The system maintains a state per next hop and per instance identifying whether allocation of statistic indexes is successful. If the system is not able to allocate all the needed indexes on a specified instance because of a lack of resources, then the user should disable egress statistics on that instance. This action frees enough statistic indexes and re-enables egress statistics on the needed entry. The selection of which other construct to release statistic indexes from is beyond the scope of this document.