Nest QoS with shaping - getting drops

[aamercado]

    HI - I have a 3800 running 12.4 with a outbound shaped nest Qos tied to a subinterface G0/0.12 which is trunk downstream to a 3500. I am getting drops on the "sh policy-manager inter g0/0.12 so know that shaping which is 1.5mbps is dropping my packets. The 3500 looks clean

3800:

policy-map A

class-map A

bandwidth 30% etc..

policy-map B

class class-default

shape 15000000 150000

service-policy A

inter gig 0/0

duplex fd

speed 100

inter gig 0/0.12

service-policy output policy-mapB

3500:

int fa0/1

switchport trunk...

duplex fd

speed 100

the routing is that host goes up to the 3800 and out a wan link but if wan is down, it hairpins back down from 3800 to 3500 which has a backup link on one of the ports. when we test wan down, or even when it is up, I see shape dropping packets

[Sergey Fer]

So what seems wrong? Shaping is not magic - it may drop packets when shaping queue fills up. How much bandwidth does your traffic consumes when wan is up?

[aamercado]

arghh...even though the QoS is explictly applied to the subinterface  gig 0/0.12, it is implicitly applied to the main

gig 0/0 so instead of G0/0 having 1000mbps, the traffic is shaped down to 1.5Mbps - There is no QoS applied to the main interface

Since the G0/0 has other subint, it is dropping traffic as a bottleneck due to this QoS.

[Joseph W. Doherty]

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

aamercado wrote:
arghh...even though the QoS is explictly applied to the subinterface  gig 0/0.12, it is implicitly applied to the main 
gig 0/0 so instead of G0/0 having 1000mbps, the traffic is shaped down to 1.5Mbps - There is no QoS applied to the main interface
Since the G0/0 has other subint, it is dropping traffic as a bottleneck due to this QoS.

Hmm, wouldn't expect it to do that. What version of 12.4 are you running?

[Sergey Fer]

Yes, I agree with Joseph - it is really unexpected. May be IOS update will help?..