Linksys SGE2000 Cisco Small Business SFE/SGE2xxx Series Managed Switches Admin - Page 26

Managing Device Information Managing Stacking 2 Unit ID as the switch being replaced. The newly inserted switch is identified by the Master unit by its Unit ID. Since the configuration of the original switch is also stored in the Master and Backup units by Unit ID, the new switch automatically receives the configuration of the old switch. This eliminates the need to configure the new switch and reduces the system downtime. The advantage of manual vs. automatic unit numbering is illustrated in the following example: A stack consists of Units 1,2,4,6,7. Unit 7 fails and an identical replacement unit is inserted. If the replacement unit is manually pre-set to be Unit 7, it can be inserted into the stack and inherit the configuration of the replaced (failing) Unit 7. However, if the replacement unit is not preset but is inserted in factory default mode (Unit 0), it is automatically renumbered to Unit 3 because that is the lowest available Unit ID in the stack. The new Unit 3 now inherits the previous unit 3 configuration. Otherwise, the system administrator must manually configure all the ports of the new Unit 3. Unit ID Conflict Resolution If two or more stacking members have the same valid Unit ID, the Master attempts to resolve the conflict by awarding the contested Unit ID to one of the units. For stacking members that are not granted the unit ID, the Stacking Master either: • Automatically resets the Unit ID to 0. The Stacking members become eligible to be reassigned another Unit ID by Automatic Unit ID Assignment. • The units are shut down. A unit that is automatically shut down remains powered on, but it is not operational, indicated by the solid red port Led. It is not a member of the stack and its connections are effectively disconnected from its immediate neighbors in the stack. If the stack is initially connected in a ring topology, the shutdown unit changes the topology into a chain. However, if the stack is initially configured in a chain topology, the shutdown unit breaks the chain. Depending on the particular configuration, may lead to other units being shut down. An automatically shut down unit remains shut down until the system administrator, manually renumbers the stacking member or removes the stacking member from the stack. A message is sent to the user that a unit failed to join the stack. The Master unit attempts to resolve Unit ID conflicts by applying the following rules: Cisco Small Business SFE/SGE Managed Switches Administration Guide 17