Stack Troubleshooting And Maintenance; Replacing A Failed Member Stack Unit In An Operational Stack - Cisco Linksys SFE2000 Administration Manual

Stack Troubleshooting and Maintenance

Replacing a Failed Member Stack Unit in an Operational Stack

If a unit that is not the Stack Master fails in an operational stack, the Stack Master discovers
that the unit is no longer responding during the Master Discovery process. The Stack Master
directs all other stack members to route unit-to-unit traffic around the failed unit using the
ring topology of the stacking connections. Concurrently, the Stack Master notifies the system
administrator of the failure by sending SYSLOG messages and SNMP traps.
Because all traffic has been routed around the failed unit, when it is disconnected from the
stack, the stack continues to run as long as all other stacking connections are left intact.
When a new unit is inserted in the stack and powered on, the following occurs:
1. The incoming unit, which is in stack mode, performs the Master Discovery process, and
may participate in the Master Election process.
• If the incoming unit has a Unit ID of 1 or 2 (it is a master-enabled unit) it initiates the
Master Election process. However, because the running Stack Master has a longer
runtime, the current Stack Master retains its position and the incoming unit does not
become the new Stack Master.
• If the incoming unit has a Unit ID of 3 through 8, it attempts to become a member
unit of the stack, subject to control by the already running Stack Master, and the
Master Election process does not occur.
2. The Stack Master performs Unit ID allocation and the conflict resolution process.
• If the incoming unit did not have an assigned Unit ID (that is, it is in factory default
mode), it is assigned the lowest available Unit ID by the Stack Master. We
recommend that you use the automatically-assigned unit ID mode because it
provides better resiliency to the stack.
• If the incoming unit already has an assigned Unit ID, and that Unit ID is unused in
the current stack, the incoming unit keeps its assigned Unit ID and the Stack Master
applies any configuration relevant to that Unit ID to the incoming unit.
• If the incoming unit already has an assigned Unit ID, and that Unit ID conflicts with a
unit ID in the current stack, the Stack Master allocates a new Unit ID to the incoming
unit, giving it the lowest available Unit ID. However, if the incoming unit has a
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Linksys One Ready Communications Solution
Chapter 3: Connecting the Switch
Stack Troubleshooting and Maintenance
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