What is the difference between all the switching modes on 6500/7600? On one of my routers, I see the following switching modes: #show fabric switching-mode Global switching mode is Truncated dCEF mode is not enforced for system to operate Fabric module is not required for system to operate Modules are allowed to operate in bus mode Truncated mode is allowed, due to presence of DFC, CEF720, Standby supervisor module Module Slot Switching Mode 1 Bus 2 Crossbar 3 dCEF 4 Bus 5 Bus 6 Crossbar 7 Bus 8 Bus 9 Crossbar What is the difference between Crossbar, Bus, and dCEF switching modes?

"Bus" is connection to 16Gbit/s bus that is common to legacy 6500 architecture.

Crossbar and dCEF mean the connection from the LC (line card) is using switch fabric (separate SFM module for Sup2, integrated switch fabric chip on Sup720 and Sup2T).

Crossbar means the connection is from the line card that doesn't have distributed processing capabilities (no DFC on it, CFC is installed), while dCEF means there's distributed CEF mode running on line card using DFC.