How does class-map match?

michael-luo · ‎09-30-2014

Say if I have two class-maps, one is matching on IP address, the other one is matching on IP Precedence, what happens if a packet meets both criteria? Which class-map it'll match?

I guess it'll be top-down (match the first class-map). If that's the case, it'd be very difficult to prioritize the class-maps as they don't have line numbers as ACLs, which you can delete/insert the class-map at a specific location in the config.

Thanks!

Wayne DeNardi · ‎10-06-2014

I'm not sure why you'd want to do this as Voice is Voice, Video is Video, Data is Data, especially if you use standardised class maps - and remember that QoS really only kicks in if the bandwidth is fully utilised, so in most circumstances with appropriately sized links, it doesn't kick in very often at all.

In any case, your question is probably better placed somewhere in the Network Infrastructure section of the forums than in the Video Over IP section you have posted it in as the solution will be based predominantly on your network equipment.

Wayne

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Joseph W. Doherty · ‎10-15-2014

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Policy-map classes are processed in sequence.

Yes, edits can be difficult, as you may need to drop and redefine multiple classes. (But we had to do that for ACLs years ago too. Fortunately, policy-map classes cannot run into the thousands.)