Dell PowerConnect 5548 User Guide - Page 47

Stack Topology The PowerConnect 5500 series systems operates in a ring or chain topology. Ring Topology In a ring topology all units in the stack are connected to each other, forming a circle. Each unit in the stack accepts data and sends it to the unit to which it is attached. The packet continues through the stack until it reaches its destination. The system discovers the optimal path on which to send traffic. Figure shows units of a stack connected in a ring topology. Stacking Failover Topology - Chain Topology Difficulties occur when a unit in the ring becomes non-functional, or a link is severed. In this case, the system automatically switches to a chain topology, without any system downtime. In chain topology, each unit in the stack is connected to neighboring unit except for the last unit, which is not connected to any other unit. In the chain topology, the stack continues to function as long as there is a master- or backup-enabled unit in each segment of the stack. When the ring topology is switched to chain topology, an SNMP message is automatically generated, but no stack management action is required. The unit that failed must be repaired to restore full stacking operation in the ring topology. After the stacking issues are resolved, the units can be reconnected without interruption, and the ring topology is restored. Stack Members and Unit IDs This section describes how to configure the stack. It contains the following topics: • Adding a Unit to the Stack • Assigning Unit IDs • Selecting the Master and Master Backup Units • Switching from the Master to the Master Backup • Replacing Stacking Members Dell PowerConnect 55xx Systems User Guide 47