Juniper Networks ERX Hardware 8 - Manual (Page 47)

Installing ERX Routers
You can install an ERX-14xx model, an ERX-7xx model, and an ERX-310
router together in the same rack. (See Figure 15.)
CAUTION: If you install an ERX-7xx model or ERX-310 router directly above an
ERX-14xx model in the same rack, you must install a plenum between the ERX-7xx
model or ERX-310 router and the ERX-14xx model so that the air can circulate
between the systems. (See Figure 51.) This plenum is available from Juniper
Networks.
If you install an ERX-14xx model above an ERX-7xx model or ERX-310 router,
there is no need to install a plenum between the units because the ERX-7xx
models and ERX-310 routers vent air out the side of the chassis.
Install heavier systems, such as an ERX-14xx model, on the bottom of the
rack. Mount lighter systems, such as the ERX-310 router, higher in the rack.
Rack-Mounted Installation 29