- Nortel Ethernet Routing Switch Owner's Manual

52 Nortel Ethernet Routing Switch 2500 Series stacking
This automatic failover is only a temporary safeguard. If the stack
configuration loses power, the temporary base unit cannot power up as
the base unit when power is restored. Also, if the original unit rejoins the
stack, it cannot resume base unit status. For this reason, always assign
the temporary base unit as the base unit until the failed unit is repaired
or replaced.
ATTENTION
If the temporary base unit is not assigned as the new base unit, and the temporary
base unit fails, the next unit in the stack order becomes the temporary base
unit. This process continues after successive failures until only two units are left
in the stack.
Redundant cascade stacking
The Nortel Ethernet Routing Switch 2500 Series allows a stack of up to 8
units 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 a stack configuration with a unit
failure in the stack. This illustrates:
• 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.
Nortel Ethernet Routing Switch 2500 Series
Overview — System Configuration
NN47215-500 (323162-B) 02.02 Standard
4.1 19 November 2007
Copyright © 2007, Nortel Networks
.