Nortel BayStack 5520-48T-PWR Install Manual page 34

34 Installation fundamentals
During the initial installation of the stack, the software automatically
determines the physical order of all units in the stack according to the
position of the base unit within the stack. Thereafter, the individual units
maintain their original unit numbering, even if the position of one or more
units in the stack is changed.
For example, when the stack is initially powered, the base unit becomes
unit 1 and the unit that the base unit connects to (via the Cascade Down
cable) becomes unit 2 (and the next unit is unit 3 and so on), until the
maximum stack configuration (up to 8 units for a 5500 Series stack or a
hybrid stack; up to 8 units for a pure 5600 Series stack) is reached. If the
base unit is changed to another unit in the stack, the new base unit keeps
its original unit number in the stack.
When a switch participates in a stack configuration, a stack MAC address
is automatically assigned during stack initialization. The stack MAC
address is the base unit MAC address plus 1. If another 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.
If an assigned base unit fails, the next unit in the stack order automatically
becomes the new temporary base unit. This change is indicated by the
Base LED on the temporary base unit LED display panel moving to a
steady amber state.
This automatic failover is a temporary safeguard only. If the stack
configuration loses power, the temporary base unit will not power up as
the base unit when power is restored. Also, if the original unit rejoins the
stack, it will not 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 will continue after
successive failures until only two units are left in the stack.
Regardless of stack configuration, the following applies:
Copyright © 2008–2009 Nortel Networks
ERS 5000 Series Installation
NN47200-300 04.03
13 April 2009