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Cisco MGX 8800/8900 Series Hardware Installation Guide
Releases 2 - 5.2, Part Number OL-4545-01, Rev. H0, May 2006
Chapter 4 Planning for Card Redundancy, Line Redundancy, and Bulk Distribution
Planning Standalone and Redundant Card Configurations
SRM cards support 1:N redundancy in the following modes:
• 1:N redundancy without bulk distribution
• 1:N redundancy with bulk distribution
The following subsections describe how 1:N redundancy operates in these two configurations and
provide guidelines for installing cards to support 1:N redundant configurations.
1:N Redundancy without Bulk Distribution
When 1:N redundancy is used without bulk distribution, you must install a special redundancy back card
for each 1:N redundant card set as shown in Figure 4-3. This redundancy back card has no connectors
on it and is installed behind the standby card.
If an active card in the 1:N redundant card set fails, the standby card takes over, and the SRM routes
communications from the standby back card through the special redundancy back card, and over to the
back card behind the failed card. This configuration allows the standby card to use the lines connected
to the back card behind the failed primary card.
Figure 4-3 Example 1:N Redundant Configuration without Bulk Distribution
The rerouting of the line communications takes place over a single redundancy bus, one of which is
installed in each bay of a Cisco MGX 8850switch. A MGX 8830 or MGX 8830/B switch has one
redundancy bus, and MGX 8850 (PXM1E/PXM45), MGX 8850/B, and MGX 8880 switches have two,
one for each bay. The redundancy bus is available to only one 1:N redundant card set at a time, so if any
1:N protected card fails in a bay, the redundancy bus is unavailable to all other 1:N redundant card sets.
To support 1:N redundancy without bulk distribution, cards must be installed according to the following
guidelines:
• The SRM-3T3/C, SRME, and SRME/B cards provide 1:N card redundancy for 8-port AUSM,
FRSM, CESM, MPSM, and VISM-PR cards that use T1 and E1 lines. Refer to Table 4-1 to see if a
specific service module supports 1:N card redundancy.
• All cards in a 1:N redundant card set (without bulk distribution) must have back cards. Each primary
card must have an appropriate back card with line connections, and the secondary card must have
the appropriate redundancy back card.
• The primary back cards in a 1:N redundancy set must all be of the same interface type. For example,
all of the cards should be either T1 or E1 back cards. Do not mix interface types in the same
redundancy set.
• When the secondary card is an AUSM, CESM, FRSM, or VISM, all cards in a 1:N redundant card
set must be of the same type. For example, a FRSM-8T1 can act as a standby card for other
FRSM-8T1 cards; it cannot serve as a standby card for an AUSM-8T1/B.
89877
Primary
CBSM T1/E1
front card
Primary
CBSM T1/E1
front card
Secondary
CBSM T1/E1
front card
SRM front
card
Primary
CBSM T1/E1
back card
Primary
CBSM T1/E1
back card
Redundancy
back card
SRM back
card