Configuring A Fallback Option - Cisco WS-C6506 Software Manual

Chapter 46 Configuring the Switch Fabric Modules
Enter the set system crossbar-fallback bus-mode | none command to specify how the packets are handled
if the Switch Fabric Module is removed or fails. If you specify the bus-mode keyword, the switching is done
in flow-through mode. If you specify the none keyword, the switch ports are disabled and switching
stops. For more detailed information, see the
The external Switch Fabric Module does not have a console. A two-line LCD display on the front panel
shows fabric utilization, software revision, and basic system information.
Note The term 9-slot switch refers to the WS-C6509-NEB and WS-C6509-NEB-A switches.
Install the WS-C6500-SFM in either slot 5 or 6 in the 6-slot and 9-slot switches. Install the
WS-X6500-SFM 2 in either slot 7 or 8 in the 13-slot switches and slots 5 or 6 in the 6-slot and 9-slot
switches. The Switch Fabric Module that is first installed functions as the primary module. For
redundancy, you can install a standby Switch Fabric Module.
When you install two Switch Fabric Modules at the same time in a 6- or 9-slot chassis, insert the primary
module into slot 5 and the backup module into slot 6. If you reset the module in slot 5, the module in
slot 6 becomes active.
When you install two Switch Fabric Modules at the same time in a 13-slot chassis, insert the primary
module into slot 7 and the backup module into slot 8. If you reset the module in slot 7, the module in
slot 8 becomes active.
Forwarding Modes
The CEF256/CEF720 modules operate in one of three modes when using centralized forwarding:
•
•
•
Table 46-2
modules installed.
OL-8978-04
Compact mode—Operational mode when all modules in the system are CEF256 or CEF720 (no
non-fabric-enabled modules can be present for this mode). In this mode, the CEF256/CEF720
modules send a "compact" 32-byte header for each frame to the supervisor engine over the switching
bus. Once a forwarding decision is made, the CEF256/CEF720 modules send the entire frame
through the switch fabric to the egress module.
Truncated mode—Operational mode when at least one non-fabric-enabled module is present in the
system. In this mode, the CEF256/CEF720 modules send the first 64 bytes of each frame to the
supervisor engine over the switching bus. Once a forwarding decision is made, the CEF256/CEF720
modules send the entire frame through the switch fabric to the egress module.
Flow-through mode—Operational mode for the CEF256 modules when there is no switch fabric present.
In this mode, the CEF256 modules send the entire packet to the supervisor engine over the switching bus.
This mode is not applicable for the CEF720 modules, which require the presence of the switch fabric.
shows the switch modes that are used with the CEF256, CEF720, and non-fabric-enabled
"Configuring a Fallback Option" section on page
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
Forwarding Modes
46-4.
46-3