Describes how RCC compares control-plane and data-plane routes to detect inconsistencies and support on-demand or background troubleshooting.
Route Consistency Checker (RCC) is a command-line tool that
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compares Routing Information Base (RIB) entries with Forwarding Information Base (FIB) entries
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detects inconsistencies between the control plane and the data plane, and
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provides details that help diagnose forwarding problems and traffic loss.
Why RCC is used
Routers in production networks can reach a state where the forwarding information does not match the control-plane information.
Possible causes include fabric or transport failures between the route processor (RP) and the line cards (LCs), or issues with the Forwarding Information Base (FIB).
RCC identifies these inconsistencies and provides detailed information about them. You can use this information to investigate the cause of forwarding problems and traffic loss.
How RCC works
RCC compares the Routing Information Base (RIB) against the Forwarding Information Base (FIB).
When RCC detects an inconsistency, the output identifies the specific route, the type of inconsistency, and additional data that supports troubleshooting.
RCC runs on the route processor. The FIB checks for errors on the line card and forwards the first 20 error reports to RCC.
RCC receives error reports from all nodes, checks them for exact matches, and adds them to either the soft queue or the hard queue.
Each queue can store up to 1000 error reports, and the queue does not prioritize entries. If different nodes report the same error, RCC logs the exact-match errors as one error.
RCC compares errors by using attributes such as prefix, version number, and error type.
RCC operating modes
RCC can run in two modes: on-demand scan and background scan.
On-demand scan
In on-demand scan mode, the user requests a scan from the command-line interface for a specific prefix in a specific table, or for all prefixes in a table.
RCC runs the scan immediately and publishes the results when the scan completes.
RCC performs on-demand scans per VRF.
Background scan
In background scan mode, the user configures a scan to run periodically during normal router operation.
The configuration specifies the interval for the periodic scan. You can configure this scan for a single table or for multiple tables.
RCC performs background scans for the default VRF and for non-default VRFs.