Packet Drops on Switch Interface

[fdharmawan]

Hi Guys,

Recently we discovered that there are packet drops on one of the switch interface in my deployment. This interface is connected to a router that is managed by other team. The initial issue was there were high latency issue on the link and sometimes packet drops. We discovered this from our monitoring. On the interface, the packet drop during a week is around 31 millions. While the reliability always 255/255, txload & rxload always below 15/255, even during the high latency issue.

I checked the CPU and memory utilization, it was normal. The CPU utilization is always below 10% while the memory utilization always at 59%.

After further research on the internet, I stumbled upon this command "show platform hardware fed switch 1 qos queue stats interface". Below is the output on my switch.

I am not sure what is the problem. Is there anything that I should check for this packet drop issue? Thank you.

[balaji.bandi]

can you post complete output

show platform hardware fed switch 1 qos queue config interface GigabitEthernet 1/0/3

try increase soft limit and - qos queue-softmax-multiplier 1200

show version also help us (we do not know the model of the device here)

[fdharmawan]

Hi Balaji,

Please find the complete output below.

I did some research on qos queue-softmax-multiplier 1200 command. On the Cisco page (https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9600/software/release/16-11/command_reference/b_1611_9600_cr/qos_commands.html), it is stated that the config should be configured along with policy-map. Although the documentation is for 9000 Catalyst. Should I configure policy-map also on my 3850 switch? Or just putting the command alone would be just fine?

[balaji.bandi]

yes 3850 still valid that command

[Joseph W. Doherty]

It often helps to mention the particulars about the device, like model, IOS being used and its feature set.

In any case, from what you describe and show, seems you might be bumping into microburst drops.

What might help is some QoS tuning (assuming its active).

See if your device will accept the command: "qos queue-softmax-multiplier 1200".

[fdharmawan]

Hi Joseph,

Apologies for missing out about the details. My current device is Catalyst 3650 and running IOS 16.9.6.

Should I configure policy map also on the interface? Currently it has none.

[Joseph W. Doherty]

You should only need to define a QoS policy, and add it to the interface, if you have a reason to override its defaults.

To your question to Balaji, I believe the qos queue-softmax-multiplier command will impact the default QoS settings on a Catalyst 3650 w/o an explicit policy on the interface.