Nortel BayStack 5520-48T-PWR Install Manual page 38

38 Installation fundamentals
The following diagram shows an example of how a stack configuration
reacts to a failed connection in the stack configuration. In the illustrated
example, the following occurs:
•
Unit 3 becomes non-operational due to a unit failure, cable
disconnection, or a loss of power.
•
Units 2 and 4, directly upstream and downstream from Unit 3, sense
the loss of link signals from unit 3. The software causes all the data to
traverse the remaining path.
•
The Cascade Down LED for Unit 2 and the Cascade Up LED for Unit 4
turn amber to indicate an error has been detected.
•
The remaining stack units continue to be connected.
There are 4 internal ports for two Cascade links. Internal ports 1 and 2
are associated with Cascade-Down link and internal ports 3 and 4 are
associated with Cascade-Up link. When viewing the event log after a
stack port goes down, use the following information to help determine the
problem:
•
Message Stack port 1 DOWN or Stack port 2 DOWN means
Cascade-Down link is down.
•
Message Stack port 1 UP or Stack port 2 UP means
Cascade-Down link is down.
•
Message Stack port 3 DOWN or Stack port 4 DOWN means
Cascade-Up link is down.
•
Message Stack port 3 UP or Stack port 4 UP means Cascade-Up
link is down.
Copyright © 2008–2009 Nortel Networks
ERS 5000 Series Installation
NN47200-300 04.03
13 April 2009