The operation of the switch stack continues uninterrupted during membership changes unless you remove the active switch or you add powered-on standalone switches or switch stacks. • Adding powered-on switches (merging) causes all switches to reload and elect a new active switch from among themselves. The newly elected active switch retains its role and configuration. All other switches retain their stack member numbers and use the stack configuration of the newly elected active switch. • Removing powered-on stack members causes the switch stack to divide (partition) into two or more switch stacks, each with the same configuration. This can cause: • An IP address conflict in your network.
If you want the switch stacks to remain separate, change the IP address or addresses of the newly created switch stacks. • A MAC address conflict between two members in the stack. You can use the stack-mac update force command to resolve the conflict. If a newly created switch stack does not have an active switch or standby switch, the switch stack will reload and elect a new active switch. Note Make sure that you power off the switches that you add to or remove from the switch stack. After adding or removing stack members, make sure that the switch stack is operating at full bandwidth. Press the Mode button on a stack member until the Stack mode LED is on.
The last two right port LEDs on all switches in the stack should be green. Depending on the switch model, the last two right ports are 10-Gigabit Ethernet ports or small form-factor pluggable (SFP) module ports (10/100/1000 ports). If one or both of these LEDs are not green on any of the switches, the stack is not operating at full bandwidth. If you remove powered-on members but do not want to partition the stack: • Power off the switches in the newly created switch stacks. • Reconnect them to the original switch stack through their stack ports. • Power on the switches.
For cabling and power considerations that affect switch stacks, see the Cisco Catalyst 9300 Series Switches Hardware Installation Guide . Stack Member Numbers The stack member number (1 to 8) identifies each member in the switch stack. The member number also determines the interface-level configuration that a stack member uses. You can display the stack member number by using the show switch EXEC command. A new, out-of-the-box switch (one that has not joined a switch stack or has not been manually assigned a stack member number) ships with a default stack member number of 1.
When it joins a switch stack, its default stack member number changes to the lowest available member number in the stack. Stack members in the same switch stack cannot have the same stack member number. Every stack member, including a standalone switch, retains its member number until you manually change the number or unless the number is already being used by another member in the stack. Managing Switch Stacks Stack Member Numbers Managing Switch Stacks 3