Simple QoS question

[wmtski666]

If I create QoS class maps to create classes based on IP precedence, and then create policy maps to apply bandwidth and queueing treatments (e.g. CBWFQ) based on those classes, am I correct in assuming precedence values other than the specific ones I've made classes for will end up being subject to whatever I've specified for the default class treatment?

If so, what happens to the routing protocol traffic?  I understand it is marked with precedence 6 - does that mean that routing protocol traffic would end up being subject to whatever treatment I've specified for the default class?

[Henrik Grankvist]

Hey

You are correct on you first assumption but on the second you are not, routing traffic have an default reserved portion of the bandwidth, which is 25% of the bandwidth on the link. This can be change with the "ip bandwidh percent ..." interface-command.

[wmtski666]

Henrik - thanks very much for the clarification.

Just to make sure I really understand this, I have a follow-up question:

If I were to make a class-map for packets marked with precedence 7, and then make a policy-map specifying some bandwidth, queuing, shaping, etc. treatment for that class, the routing protocol packets would not be subject to that treatment, right?

Or, would I need to do something like the following to explicitly exclude routing traffic from my traffic class:

class map match-all my-prec7-class

match precedence 7

no match protocol ospf

no match protocol rip

And finally, am I correct in understanding the routing protocol packets would be processed as some "hidden" class-map and policy-map, and would not be processed as part of the class-default class?

[Joseph W. Doherty]

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Posting

My understanding of CBWFQ differs from what Henrik posted.

Pre-HQF, by default, precludes defining more than 75% of the bandwidth for explicit classes, excluding class-default.  In pre-HQF CBWFQ, default reservation can be changed.  HQF CBWFQ no longer precludes, by default, the 75% limit.

Any traffic that doesn't match an explicit class becomes part of the class-default.

An you noted in your OP, routing protocols generally are marked with IPPrec 6 or DSCP CS6.

Some devices also have a special internal "PAK" priority for "special" traffic (perhaps like routing protocol packets).