Bridge Setup with Failover with redundancy fiber

RouterOS General
1

help with this !!!
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2

Use STP and set path costs to make that link a backup one.

3

Please explain HOW

4 
  A
 / \
B---C

On A:
/interface bridge
add name=bridge protocol-mode=rstp priority=0x4000
/interface bridge port
add bridge=bridge interface=to-B path-cost=10
add bridge=bridge interface=to-C path-cost=10

On B:
/interface bridge
add name=bridge protocol-mode=rstp priority=0x8000
/interface bridge port
add bridge=bridge interface=to-A path-cost=10
add bridge=bridge interface=to-C path-cost=100

On C:
/interface bridge
add name=bridge protocol-mode=rstp priority=0x8000
/interface bridge port
add bridge=bridge interface=to-A path-cost=10
add bridge=bridge interface=to-B path-cost=100

5

Thanks A lot Its Working Thanks !!!