No CLI to check router interface counters

[andriymoroz-mlnx]

Description

If packets dropped on router interface (no route or ARP resolution failed) we don’t see such counters

Steps to reproduce the issue:

1. On typical ptf32 topology send UC traffic with DST IP which cannot be routed (no route for example)
2. check "show interfaces counters"
3. no counters show drops
4. no way to check where it was dropped

Describe the results you received:

Describe the results you expected:
some utility to check router interface counters

Additional information you deem important (e.g. issue happens only occasionally):

Output of show version:
SONiC Software Version: SONiC.HEAD.6-6cf2d10
Attach debug file sudo generate_dump:

```
(paste your output here)
```

[stcheng]

could you add more information here? I wonder what would be the output of the command portstat. Will the portstat provide correct information of the drop counters for each of the interfaces?

[andriymoroz-mlnx]

portstat or "show interfaces counters" prints physical interfaces counters
if drops happen due to routing error it is not reflected there
I faced this during debugging. Maybe we need another utility to show that counters/groups of counters?

[xinliu-seattle]

Triaged, will take it with MLNX offline.