Redundancy Features; Srp Modules; Nvs Cards; Power - Juniper E120 - RELEASE 11.1.X HARDWARE GUIDE 3-25-2010 Hardware Manual

E120 and E320 11.1.x Hardware Guide

Redundancy Features

This section describes system redundancy features.

SRP Modules

The router uses a 1:1 redundancy scheme for the SRP module. When two SRP
modules are installed in the router, one acts as the primary (active) and the second
as a redundant (standby) module. Both SRP modules share a single SRP IOA located
in the rear of the chassis. After you install two SRP modules, the modules negotiate
for the primary role. A number of factors determine which module becomes the
primary; however, preference is given to the module in the lower-numbered slot.
The SRP modules record their latest roles and retain them the next time you power
up the system.
If the standby SRP module detects that the primary SRP module is not active (and
high-availability mode is not enabled), it reboots the system and takes control. If
high-availability mode has been enabled, automatic switchover occurs with near
hitless failover. For information about configuring and managing SRP module
redundancy, see JUNOSe System Basics Configuration Guide, Chapter 6, Managing
Modules.

NVS Cards

Each SRP module has two NVS cards (0, 1). The NVS cards in the active SRP module
are designated disk0 and disk1. The NVS cards in the redundant SRP module are
designated standby-disk0 and standby-disk1. After you install new NVS cards or SRP
modules, you must issue the synchronize command to match the file system of the
NVS card on the redundant SRP module with the file system of the NVS card on the
active SRP module. See "Replacing an NVS Card" on page 72 for more information.

Power

The routers provide a power architecture that distributes redundant –48 VDC feeds
through the router to each line module, IOA, SRP module, SFM module, and fan
module where DC-to-DC converters provide local conversion to the required secondary
voltages.

Fans

The E320 router employs a bottom-to-top cooling system to keep the temperature
of the modules and components within normal operating limits. Eight cooling fans
are located in a tray at the top of the router. (See Figure 1 on page 5 and Figure 2
on page 5.) Air is pulled in from the front of the router at the bottom and is
exhausted out the top.
The E120 router employs a right-to-left cooling system. Nine cooling fans are located
in a tray at the left of the router. (See Figure 3 on page 6.) Air is pulled in from the
right of the router and is exhausted out the left.
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Redundancy Features