Router User Manual

ERX Overview
After you install two SRP m od u les, the modules negotiate for the primary role.
Anumberoffac
tors determine which module becomes the primary; however,
preference is given to the module in the lower-numbered slot. The SRP modu les
record their latest roles and retain them the next time you switch on the system.
For informati
on about installing SRP modules, see “Installing Modules” on page 35.
NVS Cards
If you have two SRP modules installed in a system, you can use NVS c ards
of different
capacities on the SRP modules. The effective capacity of the
higher-capacity NVS card will equal that of the lower-capacity NVS card. For
information about installing NVS cards, see “Installing Modules” on page 35.
When you install new NVS cards or SRP modules, you must issue the synchronize
command to m
atchthefilesystemoftheNVScardontheredundantSRP
module with the file system of the NVS card on the primary SRP mod ule.
(The NVS card on the redundant SRP module will hereafter be referred to
as the redun
dant NVS card; the NVS card on the primary SRP module will
hereafter be referred to as the primary NVS card.)
If the capacity of the primary NVS card is equal to or sma ller than that of the
redundant NVS card, the system copies all the files from the primary NVS card to the
redundant
NVS card. However, if the capacity of the primary NVS card exceeds that
of the redundant NVS card, the system creates an invisible synchronization reserve
file on the primary NVS card, provided that there is enoug h space for the file.
The purpose of the synchronization file is to prevent th e creation of data that
cannot fi
t on the redundant NVS card. The file contains no useful data, and
is not visible when you view the files in NVS. The size of the file is equal
to the difference in capacities of the two NVS cards. For example, if the
primary N
VS card has a capac ity of 224 MB and the redundant NVS card has
a capacity of 220 MB, the size of the synchronization file is 4 MB, and only
220 MB of space is available on the p r im ary NVS card.
If the primary NVS card d oes not have eno u gh space to create the synchronization
reserve
file, the synchronize command fails, and a warning message is displayed
on the console. To resolve this issue, either d elete unwanted files from the primary
NVS card or replace the redundant NVS card with a higher-capacity NVS card.
Line Modules
NOTE: Th
is section applies to ERX-7xx and ERX-14xx mo dels only. ERX-310 routers
do not offer line m odule redundancy.
ERX-7xx
and ERX-14xx models support line module redundancy for several
line modules. For details about which line modules support redundancy,
see the ERX Module Guide. In thi s scheme, an extra line module in a group
Redundancy Features 17