Stacked Switch Replacement Guide

You may need to replace a faulty member switch in a stack. To prevent services from being interrupted during the switch replacement, use inter-device link aggregation to connect upstream and downstream devices for link backup.

Replace one member switch in a stack of two member switches.
SwitchA and SwitchB set up a stack. SwitchA is faulty and needs to be replaced SwitchC. You are advised to follow this procedure to complete the replacement:
1. Before the replacement, ensure that SwitchC has the same system software version and hardware model as SwitchA. To check the system software version and hardware model of switches, run the display version and display device commands.
2. Run the display stack, display stack configuration, and display stack port commands to check and record the before-replacement stack status, stack configuration, and stack port status.
3. Before connecting SwitchC with stack cables, power on it and perform the following procedure to configure it:
  1. After SwitchC starts, upload the configuration file of SwitchA to SwitchC.
  2. Run the startup saved-configuration configuration-file command to specify the uploaded configuration file as the configuration file used for the next startup of SwitchC, and then restart SwitchC.
  3. After SwitchC restarts, manually copy the stack configuration displayed using the display stack configuration command to SwitchC to ensure that SwitchC has the same stack configuration as SwitchA.
4. After the configuration is complete, check whether SwitchC has the same stack configuration as SwitchA. If so, power off SwitchC.
5. (Optional) To prevent OSPF, BGP, or LDP flapping during an master/backup switchover in a stack, configure graceful restart (GR) for the corresponding protocol. For details, see the configuration guide of the corresponding protocol.
6. Run the display stack command to check whether SwitchA is the master switch. If so, run the slave switchover command to perform an active/standby switchover in the stack. If not, go to the next step.
```
<HUAWEI> display switchover state    //Check whether the active/standby switchover conditions are met.
Slot 0 HA FSM State(master): realtime or routine backup.    //The switchover can be performed only in this state.
Slot 1 HA FSM State(slave): receiving realtime or routine data. 
<HUAWEI> system-view
[HUAWEI] slave switchover enable    //Enable the active/standby switchover.
[HUAWEI] slave switchover    //Perform an active/standby switchover.
Warning: This operation will switch the slave board to the master board. Continue? [Y/N]:y
```
  After an active/standby switchover is performed, the master switch will restart. After the switch restarts and joins the stack again, go to the next step. To check whether the switch has joined the stack again, run the display stack command.
7. Power off and remove SwitchA.
8. Install SwitchC and connect cables to its service ports, stack ports, and ports that have dual-active detection (DAD) configured.
9. Power on SwitchC so that SwitchC joins the stack as a new member. Run the display stack command to check whether SwitchC can set up a stack with SwitchB.
10. After SwitchC and SwitchB set up a stack, run the display stack configuration and display stack port commands to check the stack configuration and interface status. Ensure that the stack configuration is the same as that used before the device replacement and that interfaces become Up normally.
11. After confirming all services are normal, run the save command to save the stack configuration.
12. If the current master and standby switches are different from those before the device replacement, perform an active/standby switchover.
Replace one member switch in a stack of three or more member switches (in a ring topology).

In a stack set up by three or more member switches in a ring topology, the device replacement procedure is similar to that in a stack of two member switches. For details, see Replace one member switch in a stack of two member switches.
Replace one member switch in a stack of three or more member switches (in a chain topology).
In a stack set up by three or more member switches in a chain topology, the replacement procedure of edge switches on both ends is similar to that in a stack of two member switches. For details, see Replace one member switch in a stack of two member switches. To replace an intermediate switch, change the stack connection topology to the ring topology and then replace the switch according to Replace one member switch in a stack of two member switches. The procedure is as follows:
1. On edge switches on both ends, create a logical stack port and add member ports into the logical stack port, and then connect these ports using cables.
```
<HUAWEI> system-view
[HUAWEI] interface stack-port 1/1    //Create a logical stack port.
[HUAWEI-stack-port1/1] port interface gigabitethernet 1/0/46 enable    //Add a member port to the logical stack port.
```
  After cables are connected, run the display stack command to check whether the stack connection topology is changed to the ring topology.
2. After the stack connection topology changes to ring topology, replace the switch according to Replace one member switch in a stack of two member switches.
3. To restore the stack connection topology to chain topology after the replacement, remove the stack cables connected in step 1.