Bundle Failover Between CTP Devices at the Same Site Overview

Y-cable redundancy provides bundle failover using CTP devices at the same site. It provides a way to back up a CTP device with a redundant device at the same site, which increases circuit availability to a site (typically a remote site). The purpose of this redundancy scheme is to maximize network availability by providing complete hardware redundancy that protects from failures that include the network, chassis, processor, power supplies, and the interface module. It quickly restores communications when a system is not reachable or has failed, and is especially valuable at locations that do not have maintenance personnel or spare parts.

As shown in Figure 1, during a network or equipment failure, the affected circuit is switched to a co-located alternate CTP device and port. The process of switching the circuit to the redundant system is controlled by the AutoSwitch feature running at the hub CTP system. You need to configure AutoSwitch at the CTP hub location.

To use this feature, you use a Y cable to connect the active and standby CTP devices. With this feature enabled, the active CTP device passes data and generates keepalive messages with the standby CTP device over the Y-cable. If a failure occurs, the standby CTP device becomes active and transmits data on the circuit.

This feature requires a special Y cable (Juniper Networks part number CTP-CBL-4Q-Y). The Y cable provides control leads between the two CTP devices in addition to the standard signal, clock, and data leads connected to the attached device.

Y cable redundancy is not supported on T1 daughter cards.