Need DFC?

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Nov 26th, 2007
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Hi all.


I am deciding the purchase of equipment, and I have a question to finish.


My setup in the following:


7604-RSP720C-P Cisco 7604 Chassis,4-slot,RSP720-3C,PS)

WS-X6748-GE-TX= Cat6500 48-port 10/100/1000 GE Mod: fabric enabled, RJ-45

S763ISK9-12218SXF Cisco 7600-SUP720 IOS IP SERVICES SSH

PWR-2700-AC/4= 2700W AC Power Supply for Cisco 7604/6504-E


And as the next link says, the IPv4 routing is of Up to 450 Mpps** In hardware, where ** is Requires DFC3's.


http://www.cisco.com/en/US/products/hw/modules/ps2797/products_data_sheet09186a0080159856.html

http://www.cisco.com/en/US/products/hw/routers/ps368/products_data_sheet0900aecd8057f3b6.html


My question is about if i need a DFC Card to have IPv4 routing of up 450Mpps or not.

Or like the daugther card is a PFC (RSP 720-3C

), does it need?

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ebreniz Mon, 12/03/2007 - 09:37
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The DFC3A only supports a total of 224K FIB entries, by default there are 192K IPv4/MPLS and 32K Multicast/IPv6. If you have in your custody a linecard with a DFC3BXL, that will move your routes up to 1024K IPv4. You can achieve this also by using a card that does not have a DFC.

wochanda Mon, 12/03/2007 - 15:29
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Without a DFC, each linecard must put all input packet headers on a central bus so that the PFC on the supervisor can make a forwarding decision. The speed of this central bus limits the total PPS numbers you can achieve in a chassis. If you have all fabric-enabled cards in a chassis with no DFC's, you can get 30M PPS through the chassis. If you have a classic linecard (non-fabric), your performance is lowered to 15M PPS.


If you put a DFC on a linecard, the central bus is no longer needed for forwarding decisions, so it can process up to 48M PPS on packets coming in to it.

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