Number of class maps (QOS) supported on 7200 and 7600

Unanswered Question
Nov 12th, 2009

Hi,

Have few queries on class maps for QOS, putting forward for your comments/inputs.

1. Want to know if there are any limitation (s) on the number of class maps (to be applied inbound/outbound) that can be configured on the 7200 and 7600 routers.

2. Is there any imitation on the numbers (of class maps) in general or will it depend on the sum total of BW configured in the classes? I mean which one will be the deciding factor i.e. if the limit is wrt to the configured classes or the number of classes can't go beyond the consolidated bandwidth configured on the interface.

Kindly share details on the same and if there are any recommendations.

Thanks! in advance.

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amit.bhagat Thu, 11/12/2009 - 15:56

Hi Adarsh,

If you are using CBWFQ, you cannot create any more than 64 classes (one class per queue).

If you are using WFQ, you cannot create more than 256 classes.

In general, you cannot allocate any more than 100% of the bandwidth, provided you have configured "max reserved bandwidth" under your interface. If not, only 75% is allowed by default.

Hope to help.

Regards,

Amit.

adarsh Thu, 11/12/2009 - 23:28

Thanks! Amit for the reply, however i wanted to know if the class-map numbers limit has anything to do with the hardware platform. Kindly confirm.

adarsh Thu, 11/12/2009 - 23:31

I wanted to know if the class-map numbers limit has anything to do with the hardware platform (specifically between 7206 or 7600). Kindly confirm.

Joseph W. Doherty Fri, 11/13/2009 - 09:49

From: http://www.cisco.com/en/US/tech/tk543/tk545/technologies_q_and_a_item09186a00800cdfab.shtml

"Q. How many classes does a Quality of Service (QoS) policy support?

A. In Cisco IOS versions earlier than 12.2 you could define a maximum of only 256 classes, and you could define up to 256 classes within each policy if the same classes are reused for different policies. If you have two policies, the total number of classes from both policies should not exceed 256. If a policy includes Class-Based Weighted Fair Queueing (CBWFQ) (meaning it contains a bandwidth [or priority] statement within any of the classes), the total number of classes supported is 64.

In Cisco IOS versions 12.2(12),12.2(12)T, and 12.2(12)S, this limitation of 256 global class-maps was changed, and it is now possible to configure up to 1024 global class-maps and to use 256 class-maps inside the same policy-map."

adarsh Sun, 11/15/2009 - 23:52

Tks! for your comments.

As per your inputs and as per few documents/books related to QOS, i understand that support for QOS classes vary as per the IOS release and may number of classes supported is independent of 7206/7606 platform, till the time IOS version on two boxes is same.

Kindly correct if you feel my understanding is wrong.

Adarsh

adarsh Mon, 11/16/2009 - 00:07

Tks! for your comments.

As per your inputs and as per few documents/books related to QOS, i understand that support for QOS classes vary as per the IOS release and the number of classes supported is independent of 7206/7606 platform, till the time IOS version on two boxes is same.

Kindly correct if you feel my understanding is wrong.

Adarsh

Joseph W. Doherty Mon, 11/16/2009 - 03:47

From my read of Cisco documentation, number of supported classes is dependent on IOS version. Howerver, also note the 7200 and 7600 are two very different platforms. The 7200's IOS features, being a software based router, should fully depend on the IOS version. The 7600's IOS features depend much more on the hardware capabilities so although they too could change per IOS version they will probably be much more constrained.

Adarsh_2 Thu, 11/19/2009 - 20:03

That's nice.

From the discussion so far and as per the link provided, I understand that each sub interface can be configured for up to 64 classes (CBWFQ), ingress+egress together. Is that right, can you confirm.

Thanks!

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