Avaya 4500 Series Installation Manual page 57

unit in the stack is assigned as the base unit, the new stack MAC address is the MAC address of
the new base unit plus 1. The original stack IP address still applies to the new base unit.
Temporary base unit
If an assigned base unit fails, the next unit in the stack order automatically becomes the new
temporary base unit. The LED display on the front panel of the temporary base unit changes
to a steady amber state to indicate the change. When this happens, use the Unit Select switch
to designate the temporary base unit as the base unit until you repair or replace the failed base
unit.
You must designate a base unit because the automatic failover is only a temporary safeguard
and, if the original unit rejoins the stack, it does not resume base unit status. Also, if the stack
configuration loses power, the temporary base unit does not resume base unit status when
power is restored.
Important:
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 Avaya Ethernet Routing Switch 4500 Series allows a stack of up to eight 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.
In addition to increasing bandwidth, the software uses the cables to provide two paths between
units. If one path is interrupted, the data travels over the remaining path at half the normal
interswitch bandwidth.
Figure 19: Redundant cascade stacking
configuration reacting to a failed connection in the stack configuration.
Installation
Avaya Ethernet Routing Switch 4500 series stacking
on page 58 shows a typical example of a stack
November 2010 57