Types Of Units In Stack - Cisco 350XG series Administration Manual

Administration: Stack Management

Types of Units in Stack

Types of Units in Stack
Cisco 350XG & 550XG Series 10G Stackable Managed Switches
- A process known as Fast Stack Link Failover is supported on the ports in
a ring stack to reduce the duration of data packet loss when one of the
stack ports link fails. Until the stack recovers to the new chain topology, a
stack unit loops back the packets that are supposed to be sent through
its failed stacking port, and transmits the looped back packets through
its remaining stacking port to the destinations. During Fast Stack Link
failover, the master/backup units remain active and functioning.
The Fast Stack Link Failover feature is only active for stacks with up
NOTE
to two units. See
A unit in a stack is one of the following types:
• Master—The master unit's ID must be either 1 or 2. The stack is managed
through the master unit that manages itself, the backup unit and the slave
units.
• Backup—If the master unit fails, the backup unit assumes the master role
(switchover). The backup unit's ID must be either 1 or 2.
• Slave—These units are managed by the master unit.
In order for a group of units to function as a stack, there must be a master-enabled
unit. When the master-enabled unit fails, the stack continues to function as long as
there is a backup unit (the active unit that assumes the master role).
If the backup unit fails, in addition to the master, and the only functioning units are
the slave units, these also stop functioning after one minute. This means for
example, that if after 1 minute, you plug in a cable to one of the slave units that was
running without a master, the link will not come up.
Unit LEDs in the 550 Family
The device has 4 LEDs marked as 1, 2, 3, 4 that are used to display the unit ID of
each unit (e.g. on Unit ID 1, LED 1 is ON and the other LEDs are OFF). To support unit
IDs greater than 4, the LED display is changed in accordance to the below
definition:
• Units 1-4: LEDs 1-4 are lit, respectively.
• Unit 5: LED 1 and 4 are lit.
Stack Port Link Aggregation.
7
102