Cisco Systems IC-23 Enabling FDDI Bridging Encapsulation, Enabling Full-Duplex Mode on the FDDI

Configuring LAN Interfaces

Configuring a Fiber Distributed Data Interface

Enabling FDDI Bridging Encapsulation

Cisco FDDI by default uses the SNAP encapsulation format defined in RFC 1042. It is not necessary to define an encapsulation method for this interface when using the FIP.

FIP fully supports transparent and translational bridging for the following configurations:

•FDDI-to-FDDI

•FDDI-to-Ethernet

•FDDI-to-Token Ring

Enabling FDDI bridging encapsulation places the FIP into encapsulation mode when doing bridging. In transparent mode, the FIP interoperates with earlier versions of encapsulating interfaces when performing bridging functions on the same ring. When using the FIP, you can specify the encapsulation method by using the following command in interface configuration mode:

Command		Purpose
fddi encapsulate		Specifies the encapsulation method for the FIP.
	When you are doing translational bridging, use routing for routable protocols and use translational
	bridging for the rest (such as LAT).
Note	Bridging between dissimilar media presents several problems that can prevent
	communications. These problems include bit-order translation (using MAC addresses as
	data), maximum transfer unit (MTU) differences, frame status differences, and multicast
	address usage. Some or all of these problems might be present in a multimedia-bridged
	LAN and might prevent communication. These problems are most prevalent in networks
	that bridge between Token Rings and Ethernet networks or between Token Rings and FDDI
	because of the different ways Token Ring is implemented by the end nodes.
	We are currently aware of problems with the following protocols when bridged between Token Ring and
	other media: AppleTalk, DECnet, IP, Novell IPX, Phase IV, VINES, and XNS. Further, the following
	protocols might have problems when bridged between FDDI and other media: Novell IPX and XNS. We
	recommend that these protocols be routed whenever possible.

Enabling Full-Duplex Mode on the FDDI

To enable full-duplex mode on the PA-F/FD-SM and PA-F/FD-MM port adapters, use one of the following commands in interface configuration mode:

Command

full-duplex

or

Purpose

Enables full-duplex on the FDDI interface of the PA-F/FD-SM and PA-F/FD-MM port adapter.

no half-duplex

Cisco IOS Interface Configuration Guide

IC-40