Linksys SGE2000 Cisco SGE2000, SGE2000P Gigabit Ethernet Switch Reference Guid - Page 35

Chapter SGE2000/SGE2000P Gigabit Ethernet Switch Reference Guide 2 We recommend that when combining two stacks, you reset the switches in one stack to factory default mode and then add the switches as described in "Adding Units to a Running Stack" in the "Building Automatically-Configured Stacks" section. • If one of the merged stacks had neither a Stack Master unit nor a Backup Master unit, then units belonging to this group are inserted into the stack as described in "Replacing a Failed Member Stack Unit in an Operational Stack." The Master either connects the running units to the stack using the current Unit ID numbers or renumbers them. NOTE: Any time two stacks are combined into one stack, there is no way to maintain the configuration for both sets of switches. All dynamic information of the units that belong to the portion of the stack that was not re-elected to be the Stack Master is relearned. Understanding Stacking Cable Failure If the stacking connection cables fail and cause a stack split, the scenario described in "Merging Two Stacks" applies. This occurs only if the stack uses a chain topology. Single stacking cable failure will not cause a stack split if a ring topology is used. Inserting Too Many Units into a Stack If you try to insert too many units into a stack, when all units (existing and newly inserted) are powered on at the same time, the following occurs: 1. A Stack Master is elected following the Master Discovery and Master Election processes. 2. All other units are shut down. NOTE: Occasionally, due to a race condition during the boot process, some of the units might be connected and join the stack. When a running group of units is added to an existing stack and each one of the stack groups has an elected Stack Master, and the total of existing units and inserted units exceeds the maximum allowed number of units (8) in a stack: • The Master Detection and Master Election processes determine the Stack Master out of one of the two combined stacking groups. • When switches are added to a running stack, the Unit ID Allocation and Duplicate ID conflict resolution processes detect an error if too many switches are present in the stack, and no changes are made to units that originally belonged to the group managed by the newly-elected Stack Master. The original switches retain their ID assignments and configurations. The units that originally belonged to the group managed by the Stack Master that lost its "mastership" are shut down. Chapter 2: Managing Device Information 27 Stack Troubleshooting and Maintenance