Line card with DFC and without DFC

Unanswered Question
Jun 4th, 2007


I have sup720 on 6509 chassis....

Can I use the 6748-GE-TX line card with DFC and with DFC both in same chassis ?

If yes, What will be restriction /limitation like can i configure Etherchannel consist of 4 GE port , 2 port from 6748(without DFC) and 2 port from 6748(with DFC) line card....

Can some body help me in this ?



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Amit Singh Mon, 06/04/2007 - 07:19


You can certianly use the modules with DFC or without the DFC's in the same chassis. But why do you want that kind of config??

Using DFC's you have the complete distributed CEF forwarding on the line cards locally and the line cards download the CEF adjaceny table and FIB table locally on them. They can locally re-write the packet wihtout going to the Sup's PFC. A DFC is eventually a PFC (Policy Feature card ) that is placed on the sup engine.

To get the complete distributed architecture, you have to have DFC's on all the line cards. This will give you optimum performance on the chassis. Being said that, either have DFC's on all the line cards or on none of them. Mixing the line cards with DFC's or without DFC's will not give you a major advantage.

HTH,Please rate if it does.

-amit singh

shah.chintan Mon, 06/04/2007 - 07:41

Hi Amit,

Thanks for you response.

I do agree with you that it should be either or line card with DFC or without DFC.

But here problem is , Customer may not agree to invest immidieatly and may want to feel the advantage of DFC and then decide to go...

So Is it possible ?

And Can I have etherchannel 2 port from each line card ( with and without DFC) .B'cos Currently it is like that to avoid any outage if there is issue with any one line card so ports from other line card will make sure that etherchannel is up and no service interuption...



Amit Singh Mon, 06/04/2007 - 07:57


No issues with that config, it will work but again there will be no improved DFC performance in this case.

I am wondering what all tests we can show to have you customer convinced on the DFC performance in a mixed-mode module config.You can ask you customer to have ponly DFC installed module in the Chassis and run the tests like SSO/Failover and l3 traffic forwadin using a traffic generator.

You can involve your Cisco account team and have the customer visit to Cisco's Proof of Concet lab, where we can set up an end-end DFC tests on 6500 using the test generators.

I have myself done it for a number of customers and have got successful in showinf them the 6500 DFC capabilities.

HTH,please rate if it does.

-amit singh

shah.chintan Mon, 06/04/2007 - 08:30


I think this is good suggestion from you to involve cisco account team to test DFC capabilites..

But regarding support of etherchannle. I'm wondering if I use two port from each line card whether line card config is mix (one with DFC , other without DFC) or both with DFC how L2/L3 forwarding will happen as DFC does local forwarding here etherchanel having each of two port from each line card....will it use PFC to forward the packet in this case ???

Would apprcieate your help to understand this..



shah.chintan Mon, 06/04/2007 - 09:07

Hi Amit,

Do you have any test procedure or information on lab set up to test DFC functinality or Do I need to go to official Cisco Account team to get the same ?

Could you please suggest on this ?



Amit Singh Mon, 06/04/2007 - 09:33


Please find the attached test lab, that I used in one of my Testbed for the customer, where I wanted to show him the DFC capabilities for data forwrading. The test was designed to showcase the Non-stop forwarding of traffic with DFC's installed on each module. I had 10's of voice call active both using wired and wireless connection. We did certain tests with Sup failkure, link failure and even the complete chassis down at the core layer.

HTH,please rate if it does.

-amit singh



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