Redundant Cascade Stacking - Avaya 5000 Series Installation Manual

Installation fundamentals
stack in a cascade up (stack up) direction. The following illustration shows a cascade up (stack
up) configuration.
Figure 5: Cascade up configuration
For stack installation procedures, see

Redundant cascade stacking

The 5000 Series switches allow a stack of up to 8 units in a pure 5600 Series stack, a 5500
Series, or hybrid stack into a dual-path cascade stack. If any single unit fails or if a cable is
accidently disconnected, other units in the stack remain operational without interruption.
In addition to increasing bandwidth, the software uses the cables to provide two paths between
units. If one path breaks the data travels over the remaining path with half the normal inter-
switch bandwidth.
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
32 Avaya Ethernet Routing Switch 5000 Series Installation
Stack configuration on page 85.
December 2010