Designing and Expanding the Network 2 -29
If the primary link experiences a local or remote fault (except Low Light):
❑The backup link activates within 10 m illiseconds
❑The primary ports disconnect (that is , they do not pass data to and
from the concentrator)
However, primary port diagnostics co ntinue to operate. When the fault
clears, the primary port is enabled automatically. Once a switchover occurs,
the redundancy status indicators blink .
Each redundancy status LED (located bene ath the Activity LEDs):
❑Is off - If you disable redundancy
❑Is on - If you enable redundancy and bo th ports are operational
❑Blinks - If a switchover occurs due to a link failure
Implementing Total Backbone Fault Tolerance
You can add a backup ONline System Concentrator to provide total
backbone tolerance and lin k redundancy for your backbone network. As
shown in Figure 2-11, if the primary co ncentrator or any primary links fail,
the backup concentrator takes over. In this co nfiguration:
❑One port on the 10BASE-FB Module connects to the primary
concentrator
❑The other port connects to t he backup concentrator
You must also have a direct connecti on between the two concentrators.