A gRPC client can use the gRPC gNMI service (Get RPC, Subscribe RPC) to retrieve state information from the router that can help it make better programming decisions. All states maintained by the router (and exposed to model-driven management interfaces) are available to the gRPC client.
RIB/FIB API also introduces additional YANG state models that are complementary to the programming actions. This new state is available through the following YANG paths:
state/router/route-fib
state/router/tunnel-fib
state/router/label-fib
state/router/rib-api/route
state/router/rib-api/tunnel
state/router/rib-api/label
The corresponding show commands are also provided for reference.
The state information represented by the state/router/route-fib and state/router/tunnel-fib paths, and the show router fib-telemetry route and show router fib-telemetry tunnel show commands list are not collected by default, since it requires additional processing. In order for this state to be collected you must configure the configure router fib-telemetry command. If this command is not configured then these states are not collected at all, and telemetry subscriptions are not supported for any of the following paths:
It is not possible for a single telemetry subscription to include any of these three paths in addition to other state paths outside of this tree. This is because of the potential volume of information in the tables described in this chapter.
For gNMI telemetry subscriptions, the following restrictions should be noted:
If a route, tunnel or MPLS label entry is modified, and it covered by an ON-CHANGE subscription to a state path enabled by config>router>fib-telemetry, the update replays the current values of the entire entry (except for statistics), including values did not change from the last update. It is up to the client to compare the update to the previous one received if it needs to know the exact properties that changed.
Subscriptions to list keys of state paths enabled by fib-telemetry are not supported.