Cisco Systems IC-23 Controlling the CMT Microcode, Starting and Stopping FDDI, token capture

Configuring LAN Interfaces

Configuring a Fiber Distributed Data Interface

Controlling the CMT Microcode

You can control whether the CMT onboard functions are on or off. The FIP provides CMT functions in microcode. These functions are separate from those provided on the processor card and are accessed through EXEC commands.

The default is for the FIP CMT functions to be on. A typical reason to disable is when you work with new FDDI equipment and have problems bringing up the ring. If you disable the CMT microcode, the following actions occur:

•The FIP CMT microcode is disabled.

•The main system code performs the CMT function while debugging output is generated. To disable the CMT microcode, use the following command in interface configuration mode:

Command

no fddi if-cmt

Purpose

Disables the FCIT CMT functions.

Starting and Stopping FDDI

In normal operation, the FDDI interface is operational once the interface is connected and configured. You can start and stop the processes that perform the CMT function and allow the ring on one fiber to be stopped. To do so, use either of the following commands in EXEC mode:

Command		Purpose
cmt	connect [interface-name[phy-a phy-b]]	Starts CMT processes on FDDI ring.
cmt	disconnect [interface-name[phy-a phy-b]]	Stops CMT processes on FDDI ring.

Do not use either of the preceding commands during normal operation of FDDI; they are used during interoperability tests.

Setting FDDI Frames Per Token Limit

The FDDI interface is able to transmit multiple frames per token on a Cisco 4000, Cisco 4500, and a Cisco 4700 series routers, instead of only a single frame at a time. You can specify the maximum number of frames to be transmitted with each token capture. This significantly improves your throughput, when you have heavy or very bursty traffic.

To configure the FDDI interface to transmit a maximum number of frames per token capture, use the following commands:

	Command	Purpose
Step 1
	configure terminal	Enters global configuration mode.
Step 2
	interface fddi0	Enters interface configuration mode.
Step 3
	fddi ?	Shows fddi command options.
Step 4
	fddi frames-per-token ?	Shows fddi frames-per-tokencommand options.
Step 5
	fddi frames-per-token number	Specifies the maximum number of frames to be transmitted per
		token capture.
		Cisco IOS Interface Configuration Guide

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