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Card and Service Configuration 6-49
Redundancy Support by the MGX-SRM-3T3/B
The need for back cards and the choice of bus for redundancy support depends on whether the
MGX-SRM-3T3/B must provide bulk distribution:
• With bulk distribution, the T1 service modules do not use back cards. The MGX-SRM-3T3/B
uses the distribution bus to support redundancy.
• Without bulk distribution, the supported service modules must have back cards. The redundant
card set requires a special redundancy back card (the R-RJ48-8T1 or R-RJ48-8E!). The primary
card sets use standard back cards (RJ48-8T1 or RJ48-8E1).
With redundancy provided by the SRM, no Y-cables are necessary because the MGX-SRM-3T3/B
itself passes the traffic to the redundant front card if a failure necessitates switchover. Conversely,
any card with 1:1 redundancy supported by Y-cabling does not require an SRM. For example, the
FRSM-VHS cards have 1:1 redundancy through a Y-cable. The MGX-SRM-3T3/B redundancy
feature is particularly important for cards that do not have Y-cable redundancy—the T1 and E1
service modules.
Configuring Redundancy Through the Redundancy Bus
For redundancy that utilizes the redundancy bus, the characteristics are:
• Both the primary and the redundant front cards must have back cards. The secondary back card
must be the version specifically designed to be redundant cards. Examples are the R-RJ48-8T1
and R-RJ48-8E1, where the first “R” means redundant.
• An MGX-SRM-3T3/B can redirect traffic for only one failed card at a time regardless of the
number of redundant groups you have configured to rely on that MGX-SRM-3T3/B for
redundancy.
To configure redundancy through the redundancy bus:
Step 1 Execute addred on the active PXM:
addred <redPrimarySlotNum> <redSecondarySlotNum> <RedType>
where:
Step 2 Check the redundancy status for all cards by using dspred.
To remove redundancy, use delred.
redPrimarySlotNum is slot number of the slot containing the primary card.
The slot numbers are 1–6, 9–14, 17–22, and 25–30.
redSecondarySlotNum is slot number of the slot containing the secondary card
of the card pair. The ranges are 1–6, 9–14, 17–22, and
25–30.
RedType is a number that specifies the type of redundancy. Enter a
1 to specify 1:1 redundancy. Enter a 2 to specify 1:N
redundancy. Only an SRM can support 1:N redundancy.