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Rolling Stack Update

With the traditional firmware upgrade process, all stack members had to be reloaded at the same time to avoid a version mismatch and thus there was the need for a maintenance window.

With the Rolling Stack Update (RSU) process, downtime to the environment will be reduced from 7 minutes to few seconds.  To determine the availability to the environment you can monitore services or connections with ssh, https, rdp or ping.


Example with two stacked Cisco Catalyst 3750X switches:


1.   Verify Health of the Switch Stack


show switch detail                           Hint: The switch marked with * is the master switch

show switch stack-ring speed


2.   Set Boot Time and Enable Persistant Mac

configure terminal

boot time 7

stack-mac persistent timer 0           Hint: This command may take some seconds.


The following warnings will appear:

WARNING: Stack MAC persistency timer value of 0 means that, after a

WARNING: master switchover, the  current  stack-mac  will  continue

WARNING: to be used indefinitely.

WARNING: The  Network  Administrators must  make  sure that the old

WARNING: stack-mac  does  not  appear  elsewhere in this network

WARNING: domain. If it does, user traffic may be blackholed.


3.    Find Uplink Ports

Use the following command to identify the uplink ports

do show interfaces status

Gi1/0/23  ISL Uplink         connected    trunk      a-full a-1000 10/100/1000BaseTX

Gi1/0/24  ISL Uplink         connected    trunk      a-full a-1000 10/100/1000BaseTX

Gi2/0/23  ISL Uplink         connected    trunk      a-full a-1000 10/100/1000BaseTX

Gi2/0/24  ISL Uplink         connected    trunk      a-full a-1000 10/100/1000BaseTX


sh etherchannel summary

Group  Port-channel  Protocol    Ports------+-------------+-----------+-----------------------------------------------

1      Po1(SU)         LACP      Gi1/0/23(P) Gi1/0/24(P) Gi2/0/23(P) Gi2/0/24(P)



4.    Define Redundant Uplinks

Hint: In the uplink portchannel only one port per switch should be active. If there are more interfaces shut them down with the shut command.


interface gi/1/0/23




interface gi/1/0/24         

rsu active                        (Set this on the master switch) 



interface gi/2/0/23




interface gi/2/0/24         

rsu standby                     (Set this on all member switches)



5.    Execute RSU Procedure

archive download-sw /force-reload /rolling-stack-upgrade /overwrite tftp://

Hint: This may take about 7 minutes times the number of switches. The /reload option will not reload the switches due of unsaved changes in the running config.


6.    Monitor Update Status

show switch stack-upgrade sequence 

show switch stack-upgrade status 


7.    Force Master Switch (Optional)

After the RSU process is completed, the master switch may have changed.  If you wish to force a specific switch to become master, you will need to reload the current master switch e.g. 2.

This is done with the command below “reload slot switch-number”.  DO NOT, execute the “reload” command, as it will reload the whole stack and cause a 7 minute outage.  

show version

reload slot 2


Hint: Use in Configuration mode "switch 1 priority <1-15>" to set the switch priority. Highest value will be master.