Re: [c-nsp] N7K fabric behavior

[Tim Stevenson]

Hi Tim, please see inline below:

At 08:35 AM 12/8/2011, Tim Durack submitted:


Trying to get something clear in my mind:

N7K, 2x FAB-2, fabric redundancy, 220G capacity.

N7K, 3x FAB-2, fabric redundancy, 330G capacity.

...

N7K, 5x FAB-2, fabric redundancy, 550G capacity.


Cisco recommend a minimum of 3 FAB-2 cards. Why?



The origin of this recommendation is around M1 10G modules, which are 
80G/slot cards. So 2 fabrics give you full b/w & the 3rd gives you 
N+1 redundancy. This rule however doesn't apply to some of the higher 
performing cards (F1, F2).





If I choose to ignore this recommendation, what is the impact?

Is the fabric behavior different for M1/F1/F2 generation line cards?


The key is that Fab 2 in the chassis does not change the b/w 
capabilities of modules with a local fab 1. M1 10G cards are still 
80G/slot, F1 10G cards are still 230G/slot (with 5 fabrics).




I understand the implications of over-subscription. If a 2x FAB-2
chassis is not over-subscribed due to the mix of 1G and 10G ports,
will the fabric perform correctly? (I'm thinking yes, as this is a
simple math equation. There is no other fabric-magic going on.



Yes, you are correct - every card works and any port can talk to any 
port in the system even with a *single* fabric module. You 
(obviously) just won't get full bandwidth.


Hope that helps,
Tim




Sales-Engineering is trying to convince me otherwise :-)

Thanks for humoring me.

--
Tim:>
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Tim Stevenson, tstev...@cisco.com
Routing & Switching CCIE #5561
Distinguished Technical Marketing Engineer, Cisco Nexus 7000
Cisco - http://www.cisco.com
IP Phone: 408-526-6759

The contents of this message may be *Cisco Confidential*
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[c-nsp] N7K fabric behavior

[Tim Durack]

Trying to get something clear in my mind:

N7K, 2x FAB-2, fabric redundancy, 220G capacity.

N7K, 3x FAB-2, fabric redundancy, 330G capacity.

...

N7K, 5x FAB-2, fabric redundancy, 550G capacity.


Cisco recommend a minimum of 3 FAB-2 cards. Why?

If I choose to ignore this recommendation, what is the impact?

Is the fabric behavior different for M1/F1/F2 generation line cards?

I understand the implications of over-subscription. If a 2x FAB-2
chassis is not over-subscribed due to the mix of 1G and 10G ports,
will the fabric perform correctly? (I'm thinking yes, as this is a
simple math equation. There is no other fabric-magic going on.
Sales-Engineering is trying to convince me otherwise :-)

Thanks for humoring me.

-- 
Tim:>
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