7600 / SUP720-3BXL - mixing fabric and non-fabric enabled line cards

Unanswered Question
Mar 27th, 2008
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Dear All,

I am having to mix fabric and non-fabric enabled line cards on a single chassis.

These are my line cards:




What's the maximum expected throughput in running with mix fabric line cards ?

Also, what will be the optimal and the recommended switching mode to run (truncated vs. bus-mode) ?

Any inputs will be greatly appreciated.



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Edison Ortiz Thu, 03/27/2008 - 17:43
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Truncated Mode

Truncated Mode is used when CEF256 and/or CEF720 line cards are installed in a chassis with a classic line card, but a crossbar switch fabric is present. In this mode, classic line cards will transmit both the header and the data portion of the packet over the DBus. CEF256 and CEF720 line cards will only transmit headers over the DBus and transmit the data portion of the packet over the crossbar switch fabric.

Truncated mode results in centralized forwarding rates up to 15Mpps. In Truncated Mode, since the CEF256 and CEF720 line cards use the crossbar switch fabric to transmit data, overall aggregate bandwidth can actually be higher than the 32-Gbps shared bus capacity.

Performance of DFC enabled line cards are not affected by truncated mode and performance remains the same regardless of the line-card mix in the chassis.

More information can be found at:






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