Router User Manual

ERX 8.0.x Hardware Guide
of identical line mo dules provides redundancy in case of lin e module
failure . T o us
e this feature, you need a:
Spare line mod
ule
Redundancy mi
dplane
Redundancy I/
O module
Aredundancym
idplane can cover 3–6 slots. It provides addition al connectivity that
enablesthesparelinemoduletotakecontroloftheI/Omoduleassociatedwith
any failed line module in the redundancy group. The spare I/O module provides
connectivit
y from the spare line module to the redundancy midplane.
The process b
y which the system switches to the spare line module is called
switchover . When switchover occurs, the system:
1. BreakstheconnectionbetweentheprimaryI/Omoduleandtheprimary
line module.
2. Connects the primary I/O module to the spare line module via the redundancy
midplane and redundancy I/O m odule.
Protocol processing then takes place on the spare line module.
Figure 12 shows the data flow wh en a spare line module becomes active.
18 Redundancy Features