VSS and CFC forwarding performance

[p-blalock]

Hello,

I'm getting ready to migrate two 6509-E to VSS, each chassis has the following line cards and daughter cards:

Router>sho mod
Mod Ports Card Type                              Model              Serial No.
--- ----- -------------------------------------- ------------------ -----------
  1   20  DCEF2T 4 port 40GE / 16 port 10GE      C6800-16P10G       SAL204802JT
  2   20  DCEF2T 4 port 40GE / 16 port 10GE      C6800-16P10G       SAL204702L0
  3   20  DCEF2T 4 port 40GE / 16 port 10GE      C6800-16P10G       SAL204905AL
  6    5  Supervisor Engine 2T 10GE w/ CTS (Acti VS-SUP2T-10G       SAL202900NU
  7   24  CEF720 24 port 1000mb SFP              WS-X6724-SFP       SAL12351Y57


Mod  Sub-Module                  Model              Serial       Hw     Status
---- --------------------------- ------------------ ----------- ------- -------
  1  Distributed Forwarding Card C6800-DFC          SAL204802JT  1.2    Ok
  2  Distributed Forwarding Card C6800-DFC          SAL204702L0  1.2    Ok
  3  Distributed Forwarding Card C6800-DFC          SAL204905AL  1.2    Ok
  6  Policy Feature Card 4       VS-F6K-PFC4        SAL202601AH  3.0    Ok
  6  CPU Daughterboard           VS-F6K-MSFC5       SAL202900EV  3.1    Ok
  7  Centralized Forwarding Card WS-F6700-CFC       SAL12372XVF  4.1    Ok

I'd like to know what impact the WS-F6700-CFC will have on forwarding performance given that the other line cards have the C6800-DFC?

Thanks

[Reza Sharifi · Accepted solution]

Hi,

There should not be a major performance impact.

Here is a good doc explaining the difference.

https://supportforums.cisco.com/document/85621/understanding-msfc-pfc-and-dfc-roles-catalyst-6500-series-switch#Centralized_Forwarding_Card_CFC

HTH

[p-blalock]

Thanks for that Reza, but does this also apply to the performance while running this card, with CFC,  in VSS mode with the other cards that have DFC4?  I don't see any explanation related to VSS.

[Joseph W. Doherty]

There's really no special performance consideration related to VSS.

All VSS buys you, from a performance standpoint, is, ideally, half you traffic is processed by each VSS member, so, in theory, VSS can offer twice the performance of a non-VSS individual platform.

Ingress traffic on your non-DFC line card will be processed by your sup.  Your sup2T is rated at (I recall) 60 Mpps.  As your other line cards have DFCs, all your sup's PSS can be devoted to your one non-DFC line card (and its own 10g ports).  (BTW, minimum size Ethernet requires about 1.5 Mpps per gig, so your 24 gig port card could require up to about 36 Mpps.)