Juniper Networks ERX Hardware 8 - Manual (Page 36)

ERX 8.0.x Hardware Guide
of identical line modules provides redundancy in case of line module
failure. To use this feature, you need a:
Spare line module
Redundancy midplane
Redundancy I/O module
A redundancy midplane can cover 3–6 slots. It provides additional connectivity that
enables the spare line module to take control of the I/O module associated with
any failed line module in the redundancy group. The spare I/O module provides
connectivity from the spare line module to the redundancy midplane.
The process by which the system switches to the spare line module is called
switchover . When switchover occurs, the system:
1. Breaks the connection between the primary I/O module and the primary
line module.
2. Connects the primary I/O module to the spare line module via the redundancy
midplane and redundancy I/O module.
Protocol processing then takes place on the spare line module.
Figure 12 shows the data flow when a spare line module becomes active.
18 Redundancy Features