Catalyst 9300 - fed switch active fwd-asic drops exceptions


I’m looking for an explanation for the following command + part of the output :-

show platform hardware fed switch active fwd-asic drops exceptions

Specifically around the PKT_DROP_COUNT - this is incrementing continually and need to know if its an issue and how to go about combatting it, not seeing any drops on interfaces / output drops etc.

I’ve looked inside the IOS-XE 17.3.x command ref guide and don’t see any mention of this, or any info from CCO.

Any help is much appreciated.


Hello Morgan

That seems very strange. The command should be preceded by a show platform and should be something like this:

show platform hardware fed switch active fwd-asic drops exceptions

In any case, this command displays hardware information about the fwd-asic which is a hardware resource of the device. It’s not looking at any particular interface, but at the ASIC which processes packets before they are sent on the physical interface.

What you’re seeing here is drops due to hardware limitations. These won’t show up as drops on interfaces, because the drops are occurring before the packets reach the interfaces. On some platforms, multiple interfaces share a single ASIC, so there is not always a one-to-one correspondence between ASIC and interface.

Now what is this particular drop count and how do we deal with it? ASICs are involved in processing packets when QoS is employed. They do things like managing buffers, applying QoS mechanisms and doing some of the processing that the central CPU would otherwise do.

I suggest the first thing to look at is to see if you have congestion on the network, and check what QoS mechanisms are kicking in. Also, examine the actual performance of the network. Are you seeing a slow down in the network which prompted you to investigate and you found these counters or did you come across them simply by chance?

Let us know some details of your topology as well, and what QoS configurations you have configured so that we can help you further.

I hope this has been helpful!


Hi Laz,

Very informative + thanks for the response. I think I need to baseline the traffic patterns on this customers piece of kit + see what day to day usage is like etc, also I know for fact there not using any specific QoS (except out the box setup).

Again most informative and gives me something to look at / think about.

Much Appreciated.

Hello Morgan

Some platforms (like the Nexus devices) have preconfigured common QoS configurations by default. From the 9300 documentation for IOS-XE release 16.6, QoS is enabled by default.

Glad to hear that it has been helpful, keep us informed about your progress, and if you need anything else, you know where to find us…

I hope this has been helpful!