Installation guide

4-82 Cisco 4000 Series Installation Guide

Network Connection Considerations

Figure 4-38 Single-Attachment Multimode FDDI Module—End View

Optical Bypass Switch Connections

Both the dual-attachment and single-attachment FDDI modules have an optical bypass

switch connector. An optical bypass switch is a passive optical device powered by the FDDI

module. If a fault in the router occurs, or if power is lost, the optical bypass switch is

enabled, and the ring will be unaffected. The optical bypass switch is automatically enabled

if power is lost. In addition, the system software can enable the optical bypass switch if a

problem is detected or if the operator chooses to take the router out of the ring.

BRI Connections

The Basic Rate Interface (BRI) network processor modules (see Figure 4-40 and

Figure 4-39) support either four or eight BRI ports. Each BRI port is an RJ-45 8-pin

connector. Use an appropriate cable to connect the BRI module directly to an Integrated

Services Digital Network (ISDN) through an ISDN channel service unit/digital service unit

(CSU/DSU) called the NT1. The common carrier will provide the NT1 connection, except

in North America, where the NT1 is customer owned.

H1401a

PHY-S

FDDI

OPT-BYPASS

Multimode port

Alignment groove

Optical bypass

switch connector

LED

PHY-S

RING OPT

Mounting

screw locations