Cisco Systems BC-109 manual Enable or Disable the Source-Route Fast-Switching Cache

Tune the SRB Network

Enable or Disable the Source-Route Fast-Switching Cache

Rather than processing packets at the process level, the fast-switching feature enables the Cisco IOS software to process packets at the interrupt level. Each packet is transferred from the input interface to the output interface without copying the entire packet to main system memory. Fast switching allows for faster implementations of local SRB between 4/16-MB Token Ring cards in the same router, or between two routers using the 4/16-Mb Token Ring cards and direct encapsulation.

By default, fast-switching software is enabled when SRB is enabled. To enable or disable source-route fast-switching, use one of the following commands in interface configuration mode:

Command	Purpose
source-bridge route-cache	Enable fast-switching.
no source-bridge route-cache	Disable fast-switching.

Note Using either NetBIOS Byte Offset access filters or access expressions that combine access filters disables the fast switching of source-route bridging frames.

Enable or Disable the Source-Route Autonomous-Switching Cache

Autonomous switching is a feature that enables the Cisco IOS software to transmit packets from the input ciscoBus card to the output ciscoBus card without any involvement on the part of the router processor.

Autonomous switching is available for local SRB between ciscoBus Token Ring (CTR) cards in the same router. Autonomous switching provides higher switching rates than does fast switching between 4/16-Mb Token Ring cards. Autonomous switching works for both two-port bridges and multiport bridges that use ciscoBus Token Ring cards.

In a virtual ring that includes both ciscoBus Token Ring and 4/16-Mb Token Ring interfaces, frames that flow from one CTR interface to another are autonomously switched, and the remainder of the frames are fast switched. The switching that occurs on the CTR interface takes advantage of the high-speed ciscoBus controller processor.

To enable or disable source-route autonomous switching, use one of the following commands in interface configuration mode:

Command	Purpose
source-bridge route-cache cbus	Enable autonomous switching.
no source-bridge route-cache cbus	Disable autonomous switching.

Note Using either NetBIOS Byte Offset access filters or access-expressions that combine access filters disables the autonomous switching of SRB frames.

BC-140Bridging and IBM Networking Configuration Guide