Switch Features 57
Master Failover with Transparent Transition
The stacking feature supports a 
Standby
 or backup unit that assumes the 
Master unit role if the Master unit in the stack fails. As soon as a Master 
failure is detected in the stack, the Standby unit initializes the control plane 
and enables all other stack units with the current configuration. The Standby 
unit maintains a synchronized copy of the running configuration for the 
stack. 
Nonstop Forwarding on the Stack
The Nonstop Forwarding (NSF) feature allows the forwarding plane of stack 
units to continue to forward packets while the control and management 
planes restart as a result of a power failure, hardware failure, or software fault 
on the stack management unit. This type of operation is called nonstop 
forwarding. When the management unit fails, only the switch ASICs on the 
management unit need to be restarted.
Hot Add/Delete and Firmware Synchronization
You can add and remove units to and from the stack without cycling the 
power. When you add a unit, the Stack Firmware Synchronization feature 
automatically synchronizes the firmware version with the version running on 
the stack master.  The synchronization operation may result in either upgrade 
or downgrade of firmware on the mismatched stack member.
Security Features
Configurable Access and Authentication Profiles
You can configure rules to limit access to the switch management interface 
based on criteria such as access type and source IP address of the 
management host. You can also require the user to be authenticated locally or 
by an external server, such as a RADIUS server.
For information about configuring access and authentication profiles, see 
"Controlling Management Access" on page 169.