Avaya 4500 Series Installation Manual page 58

Installing the Avaya Ethernet Routing Switch
Figure 19: Redundant cascade stacking
1. Base Unit
2. Last Unit
3. Unit selector switch
4. Cascade Cable
In the example, the following occur:
• Unit 3 becomes nonoperational 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 directs 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.
• The remaining stack units remain connected and continue to operate.
Replacing or adding a stack unit
To replace a failed stack unit or insert a new unit into a stack, perform this procedure.
Important:
Automatic Unit Replacement (AUR) for both configuration and software is enabled for all
Avaya Ethernet Routing Switch 4500 Series platforms and software releases. This means
that the agent code image, on a replacement unit, is automatically upgraded or downgraded
58 Installation November 2010