Sflow might report outgoing interface incorrectly when the following conditions are met.

· An overlapping route with longer prefix length (e.g.1.1.2.0/24 to IF1) exists simultaneously with a shorter prefix length (e.g., 1.1.0.0/16 to IF2) in RIB/FIB.

· If packet from shorter prefix length arrives first, then entry for it gets added to sFlowd cache first.

· Next if packet from longer overlapping prefix arrives it will match to entry of smaller prefix in sFlow cache and will point to NH and OIF of shorter prefix length.

Incorrect OIF can be noticed at the sflow collector

its known limitation as of now on Junos Evo.

You can evaluate sflow egress sampling to avoid incorrect OIF issue with the shortest and longest matching prefixes.

Please reach out to JTAC with the complete details.