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Community Member

catalyst 65xx and dfc3b cards


don't understand why should I order dfc3(a,b,bxl) cards for such modules as WS-X6724-SFP=?

Need your advice.

Links for docs are desirable.



Re: catalyst 65xx and dfc3b cards

you would use the DFC3 card deployed on your CEF 720 line card, such as the 6724-SFP, if you require a higher aggregate environment or line card localized forwarding decisions.

(the DFC3 will provide localized forwarding decisions for each line card it is deployed on.)

a benefit is an increased aggregated system performance upto 400mpps.

the 3B and 3BXL also provide MPLS support enhancements and ACE counters.

the 3BXL also has the scalability to support 1 million IPv4 routes and 256kb netflow entries.

please see the following link for more info:

Community Member

Re: catalyst 65xx and dfc3b cards


thanks for your answer...

but still don't understand..((

if Supervisor 720 has an integrated switch fabric providing 2x 20 Gb connection to each module slot, why should we use DFC, if we already have 40Gb per module?

and the 2-nd point:

720 Gbps using Cisco Express Forwarding and 30 Mpps per system

Why 720 Gbps and only 30 Mpps ???


Community Member

Re: catalyst 65xx and dfc3b cards

The 2 x 20Gig fabric connections are one for teh active and one for the standby supervisor. So you are down to one 20Gig connection. Also, the DFC2 allows to switch autonomously on tge card because a copy of the supervisor FIB table is dopwnloaded to the DFC3 on the line card (the DFC3 is a PFC to all intents and purposes. This means with a system of heavily utilised line cards you can get line rate performance from the interfaces on evey card in the system without bothering the supervsior engine.

The 30mps applies when you use older line cards such the 61 and 63 series. These line cards - called "classic cards" do not connect to the crossbar fabric on the supervisor engine. These cards are instead connected to the shared bus on the backplane. The supervisor engine has to apply bus arbitration logic (who can transmit and receive form the bus and when)to the line cards and all this slows the speed down to a maximum of 30mpps, irrespctive of chassis.

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