CBWFQ on GigE Subinterfaces

Answered Question
Sep 4th, 2009

I have CBWFQ on subinterfaces on a PA-GE on a 7507. I will be migrating to a 7206VXR shortly. It's showing that CBWFQ is not supported on subinterfaces. Is there a QoS method for larger links like this? Is one really necessary? wr currently use it in the current environment to have less latency- I need to know what the best practice for QoS on large links (GigE) is.

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Joseph W. Doherty Fri, 09/04/2009 - 16:14

Generally, and until recently, the QoS supported on ISRs and 7200s has fewer features than what's available on the 7500s.

I'm not at a 7200 to try, but it might be the CBWFQ issue you see on subinterfaces has to do with CBWFQ not "knowing" the bandwidth involved. It might work if you define a parent policy with a shaper, and then a subpolicy with your classes.

Additionally, Cisco's very recent IOS QoS works much like a 7500; subinterface issue might have been addressed (don't recall for sure). You need the HQF QoS variant, available in 12.4(20)T and later, I believe.

gregwoodson Tue, 09/08/2009 - 07:46

I tried both the sp services and service provider code- 12.4(24)T and T1- with no success- is it a different type of code I should be looking for?

gregwoodson Tue, 09/08/2009 - 08:13

class-map match-any voice

match access-group name voice

match dscp ef

match dscp cs6

match mpls experimental topmost 5

policy-map output-qos

class voice

bandwidth percent 30

class class-default

fair-queue

interface GigabitEthernet2/0.51

MMR-ACC-1(config-subif)#service-policy output output-qos

CBWFQ : Not supported on subinterfaces

MMR-ACC-1(config-subif)#

Joseph W. Doherty Tue, 09/08/2009 - 16:40

Ah, that link works. Thanks.

Yes, I knew you could use a shaper, and mentioned that in my original post. I didn't provide more information on this technique since OP's original question was to make QoS work like 7500 (which I recall[?] doesn't require a shaper). Glad you provided reference, since OP indicates it resolves their issue.

However, to the original poster, the HQF QoS variant is much more like the 7500's QoS. For instance, you can enable FQ in other than class-default and class-default's FQ adheres to class bandwidth allocation.

As I also noted, though, I wasn't sure whether QoS within a subinterface now worked directly. Rereading the whitepaper and config guide on it, (http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6558/white_paper_c11-481499.html and http://www.cisco.com/en/US/docs/ios/qos/configuration/guide/qos_frhqf_support_ps6441_TSD_Products_Configuration_Guide_Chapter.html), I don't believe it does. I.e., what Edison provided is still required.

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