Total output drops due to QoS

[mac_mac_net83]

Hi members, 

I am currently troubleshooting a Gig interface that has increasing total output drops value.

The Gig interface is connecting to a switch. We use subinterfaces on the router to connect to different circuits. 

I noticed that the total output drops value we have on the GiG interface matches the packets being dropped on one of the subinterfaces due to qos policy. The subinterface only is limited to 30M and will be dropped if there is violation of this CIR.

My question is , is there a specific command , "show interface" whatever that will tell that the total output drops is due to QoS policies instead of the Gig interfaces being congested ??

Thank you.

Mark

[Georg Pauwen]

Hello,

the command:

show policy-map interface X

should tell you what your policy does and if packets are being dropped due to the policy being configured on your interface...

[mac_mac_net83]

Hello Georg,

That is what I did. It maybe overwhelming though looking at the QoS counters as well as its difficult to check if it is historical or not and sometimes depending on how your QoS is configured (nested, etc.) , you need to do some math to check and get the total of each drops to see if it matches the total output drops on the "show interface" command.

What I am wondering is if there is a command besides that , that will tell you..."ah you are dropping because of your policy-maps and not the interface is congested.. :-). My idea is it could be dropping in software, so I am looking for a command that will show those kind of drops...if there is such a thing :-)

[Giuseppe Larosa]

Hello Mark,

as far as I know the show policy-map interface is the only command that allows you to perform this kind of checks.

This show command accepts additional parameters so that you can see only input section or output section and you can also specify a class-map <name>.

This can be handy if you know what class(es) are experiencing drops.

Of course, some calculations are needed.

Hope to help

Giuseppe

[Joseph W. Doherty]

Like the others I'm unaware of such a command, but what you're asking for is drops due to just logical congestion vs. physical congestion that also causes logical congestion. I.e. the former would be due to a shaper or policer, the latter due do the physical interface, itself, being congested.

Since as the others have also noted, this can be determined by examination/analysis of policy-map interface stats, I doubt Cisco could be talked into providing such a command, but you could suggest it as a feature request.