C3850 QoS Service-policy output

[MATTHIAS SCHAERER]

Hi 

I try to apply the following config. The command interpreter does not seem to allow me to do that, no error message but no policy map is attached to any interface. I tried to attach it to the physical interfaces too, without success. Any known reasons for that behaviour?

class-map match-any CM-OUTPUT-DROPS
 match vlan 1500 1560 3012 4000
!
policy-map PM-OUTPUT-DROPS
 class class-default
 bandwidth percent 100
!
interface Port-channel1
 service-policy output PM-OUTPUT-DROPS

[Joseph W. Doherty]

Regarding no error messages, did you also check you syslog?

You might try bandwidth percent 99 or bandwidth remaining percent 100.

[MATTHIAS SCHAERER]

Hi Joseph

The hint with the log was good, first it did not like the config on Port-Channel interfaces but also when I configured it to the physical interfaces it looked like that:

Mar 9 10:55:11.399: %QOS-6-POLICY_INST_FAILED: 
 Service policy installation failed 
Mar 9 10:58:02.467: Order of classes in policy name PM-OUTPUT-DROPS is not consistent with 
installed policy

I cannot yet see what in the order of my policy should be wrong since it consists of one class only but I'll sure find out. The 99% by the way lead to the same error.

I tried to rephrase the class-map, without success:

class-map match-any CM-OUTPUT-DROPS
 match vlan 1500
 match vlan 1560
 match vlan 3015
 match vlan 4000

The fun thing is that I have a pretty similar config, only with an IP access group on a 3650 that is running perfectly. I guess it must have something to do the the VLAN-based matching criteria.

Thanks for your hints. I'll keep trying.

[MATTHIAS SCHAERER]

I found this page, which puzzles me a bit:

http://www.cisco.com/c/en/us/support/docs/switches/catalyst-3850-series-switches/200729-Common-QoS-error-messages-on-Catalyst-38.html#anc11

It says something like

Restriction(s):

• The classification sequence for all wired queuing-based policies should be the same across all wired upstream ports (TenGigabit Ethernet), and the same for all downstream wired ports (Gigabit Ethernet).

Workaround:

• Use the same order of the classes as the first configured queueing-based policy-map. This message is not shown if you apply the policy map on any interface of 10GE Module

So in other words this means that I can have one input and one output policy over all ports in one module. Or am I wrong in my interpretation? It would at least explain my issues, I'd have to find another solution in this case.

[Joseph W. Doherty]

Yea, it could mean that as "under the covers" Catalyst switches support QoS via hardware.

I also just notice you're trying to apply the service policy to a port-channel.  You might also try applying to the individual port-channel ports.

[MATTHIAS SCHAERER]

Hi Joseph

As I said before I also tried to apply the policy-map to physical interfaces with the same result.

QoS in switches sure must be a hardware thing, otherwise the switching performance would be degraded greatly. The difficulty is to find out how to instruct each device to do what I want (or rather to know what the device allows me to configure QoS-wise). I have not yet found any documentation that lets me dig into each box to understand the inner workings.

Thanks for your ideas

P.S. Sorry for the one star. I meant to give 5 but I can't handle the tool.....

[Joseph W. Doherty]

Yup, QoS in switches is very much a hardware thing, for the reasons you note.

Although you cannot generally "see" the impact against particular/specific flows, you can often infer much from the QoS stats that device does provide especially relative to your QoS configuration.

[Feds]

Hi Matthias,

Can I ask you which IOS-XE was your 3850 running at that time? We ran into the same issue and we got

%QOS-6-POLICY_INST_FAILED:
Service policy installation failed

but no further hint or message like the one you were getting. Our 3850 is running 3.6.8E.
I suspect the reason we can't configure a different service-policy out on one single Gix/0/x interface is the same in both our cases (BTW thanks for that URL) however I was wondering why we don't get the extra info.

Cheers!
F.