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MMI's IP interfaces will never be synchronised, however, the IP addresses of the other interfaces on all slave
modules will be synchronized.
12.5.4 LINK BETWEEN MMIS
MMI Redundancy is highly dependent on external link between MMI modules. Link down state is notified to the
user as an "Unable to communicate with Twin MMI" critical alarm, and there are important consequences on this
feature if the link is down:
• Database synchronisation will not be available. This will be shown on Synchronization status.
• The mechanism to enforce all modules to be logged into the same backplane will not work, as each MMI
has no information about the other.
• Cards logged into one MMI will not be shown on the other. This will be shown as 'Not present' and 'Card
missing' alarms.
• No switch will be available as the mechanism to move modules from one side to the other is not working.
When the link is restored, and Main MMI is running properly, there are two possible situations:
• There is no MMI switch registered, so there is no reason to stay in Backup MMI. All cards will be forced to
switch back and Main MMI will be Active again.
• There is a MMI switch registered. This means either manual or automatic (triggered by alarms) MMI switch
was performed before losing contact with twin MMI (link down). Depending on the switching mode, a
decision will be taken: If 'Once' mode, cards will stay in the second backplane and Backup MMI will be
Active; if 'Reverting' mode, cards will be forced to switch back to Main MMI, which will become Active.
12.6 MONITOR IN/OUT REDUNDANCY
The Monitor In/Out Redundancy is designed as an alternative for configurations that require IP output
redundancy, but that cannot use OSPF or an Active+Active configuration. This configuration is made up of the
primary unit with a Switch+IP module in Cloned IP Output mode and a secondary unit with a Switch+IP in
Monitor In/Out mode which monitors the active output from the primary and if in error will activate its outputs.
The configuration of this is as follows
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