Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?

 
ON THIS PAGE
 

Packet Forwarding Engine Install Error Checking

(Junos OS Evolved only) This error checking mechanism enhances network resiliency by enabling the forwarding plane to notify the control plane of any next-hop installation errors, thereby maintaining accurate routing states and preventing traffic loss. Errors from multiple Packet Forwarding Engines are aggregated and reported in a consolidated manner, simplifying error detection and resolution processes.

We have more than one copy of routing information present in a router. Two such repositories are the Routing Information Base (RIB) and the Forwarding Information Base (FIB). The control plane computes the data flow packet path and stores the data in the RIB. A subset of this data is propagated to the forwarding plane ASIC and is stored in the FIB, which finally gets programmed in the forwarding ASIC in the Packet Forwarding Engine (PFE).

Sometimes the routing information present in the RIB is not correctly installed in the FIB. The control plane owning the RIB might not have information about the discrepancy between the contents of the RIB and that in the forwarding plane. This discrepancy might result in the control plane protocol publishing a state of the routing path that is not accurate. Eventually this might lead to other problems, including traffic loss.

Use Feature Explorer to confirm platform and release support.

Benefits of Packet Forwarding Engine Install Error Checking

  • Enables the forwarding plane to notify the control plane of any next-hop installation errors, thereby maintaining accurate routing states and preventing traffic loss.

  • Errors from multiple Packet Forwarding Engines are aggregated and reported in a consolidated manner, simplifying error detection and resolution processes.

  • Covers various next-hop types, ensuring broad error detection and notification, which contributes to the reliability of network operations.

Enable and Monitor PFE Install Error Checking

To enable this error checking, configure the pfe-install-error statement at the [edit routing-options forwarding-table]​ hierarchy level, then restart the rpd process. Two operational mode CLI commands are available to check on these route errors after you have configured this feature:

  • If the forwarding plane is not forwarding traffic, use the show route pfe-install-error command to ​check if the Packet Forwarding Engine has sent an error for the route that is dropping traffic​.

  • To check for next-hop errors, use the show routing nhdb pfe-install-error command. We support errors for routes pointing to a limited set of next hops: RT_NH_INDIRECT, RT_NH_ROUTER, RT_NH_CHAIN, RT_NH_INDXD, RT_NH_LIST, RT_NH_TUNNEL_COMP, and RT_NH_FRR_INDIRECT​.

This feature does support sharding, ensuring that routes with sharding enabled will also handle next-hop errors appropriately without breaking the sharding functionality. In scaled scenarios, not all errors generated may be displayed due to limitations in error message handling. The Packet Forwarding Engine will only report next-hop installation failures, which are the most probable type of error.

Related Documentation