In reply to AXEL PILZ.

1. 250, 350, 350X and 550X series can be managed in SNA. 200, 300 and 500 series can only be discovered. 220 series does not support SNA at this time. 110/100 series are unmanaged switch, and thus cannot be discovered or managed in SNA. ;
2. There is no concept of backup management switch in SNA. All 350, 350X and 550X series switches in your network can be used as management switch. You don't need to specify one switch as the management switch. Log into any of the switch, and you can choose to view the SNA interface. And if a particular switch is down, you can use the SNA interface on another switch. It's totally flexible and no single point of failure.