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CEF and QoS

Does anybody have a good reference to explain why many QoS features require CEF to be enabled, and how the two interact?  I've seen the Cisco doc:

http://www.cisco.com/en/US/tech/tk39/tk824/technologies_tech_note09186a0080094978.shtml

But this only tells you *when* it's needed and not why.  I'm interested to know about how the entries in the FIB must be used to determine how packets are marked up and queued.

If anyone could point me in the right direction, I'd be grateful!

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Re: CEF and QoS

hello,

CEF rarely needs to drop a packet, even if it is the first packet of a new flow, it is able to operate much more efficiently than Fast Switching. And because it caches the entire routing table, it is even able to do packet-by-packet round-robin load sharing between equal cost paths. CEF shows its greatest advantage over Fast Switching in situations when there are many flows, each relatively short in duration. Another key advantage is that CEF has native support for QoS, while Fast Switching does not

check this link for QOS

please rate if this helps

thanks

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