This article addresses an issue on the PTX10001 EVO platform where traffic may be unexpectedly dropped due to uRPF (unicast Reverse Path Forwarding) failures. This situation occurs when both the default route and a source route share the same forwarding traits, leading to potential route compression in the FIB (Forwarding Information Base).

Traffic may be dropped unexpectedly when uRPF is enabled.

The drop is classified in the PFE (Packet Forwarding Engine) by the trap code: dlu.ipipe.err.trapcode.rpf[0].

To mitigate this issue, consider the following workarounds:

1. Add Source Class Attribute:

- Implement a policy to add a source class attribute, preventing the source route from being compressed into the default route:

set policy-options policy-statement scu-policy term 0 from route-filter <specific-route> orlonger

set policy-options policy-statement scu-policy term 0 then source-class scu-a

set routing-options forwarding-table export scu-policy

2. Reject Default Route:

- Apply an import policy to reject the default route so that packets do not hit the default route, avoiding drops.

3. Disable FIB Optimization:

- Disable FIB optimization to prevent route compression for routes with the same forwarding properties, ensuring all individual routes are installed into the FIB. Note that this may increase the route scale:

set chassis fib-optimization family inet disable

There is known PR1809955 describing this issue and its resolved in following release:

https://prsearch.juniper.net/problemreport/PR1809955

evo:21.4R3-S8-EVO

evo:21.4R3-S9-EVO

evo:22.2R3-S5-EVO

evo:22.3R3-S4-EVO

evo:22.4R3-S3-EVO

evo:22.4R3-S5-EVO

evo:23.2R2-S3-EVO

evo:23.4R1-S2-EVO

evo:23.4R2-EVO

evo:24.2R1-EVO

evo:24.2R2-EVO

evo:24.3R1-EVO

evo:24.4R1-EVO

evo:25.1R1-EVO

2024-09-23 : Article Created

2024-10-10 : PR ext link added