We currently have a stack of Catalyst 9300, like this :

SW1 (master)



We plan on adding a 4th switch, SW4, but in between SW2 and SW3. This would give:





My question is : would that impact our configuration ? What I mean is that as it stands, port 1 on SW3 has configuration and is referenced as Gi3/0/1. If SW3 now becomes the switch at the bottom, would we still address the port as Gi3/0/1 or as Gi4/0/1 ? And would the Gi3/0/1 configuration now be applied on the newly added switch in the middle, or remain active on the switch at the bottom ?

Would we need to renumber one of the switch ?


1 Answer 1


The order in which the switches are physically connected does not matter to the configured switch number. The switches are connected in a loop, so there is really no top or bottom, even if there is a physical top and bottom in a rack.

If you correctly configure the switches, you would have specifically set the switch numbers in the switch before building the stack, and adding a switch anywhere in the stack will not change the switch numbers, so the interface numbers will stay the same.

You should also specifically set the switch priorities, which do not need to relate to the switch numbers. For example, Switch 3 could be the master, and Switch 1 could have the next highest switch priority, becoming the master if Switch 3 goes down.

  • Alright, for future reference, I will then configure "switch 1 renumber 4" on my new switch before adding it to the stack.
    – user53632
    Mar 1, 2019 at 17:31
  • You set the switch priority using, for example: switch 1 priority 15 and then switch 2 priority 10 - switch 3 priority 8 etc. 15 is the highest priority.
    – user36472
    Mar 1, 2019 at 17:47
  • @Cown, one interesting thing we have run into is our Operations group deciding that no switch should be set to 15, so we start with 14 and go down from there. I'm not sure of the reason for the decision, but it may be that they would want to put in a higher priority switch at a later time for some reason.
    – Ron Maupin
    Mar 1, 2019 at 17:49
  • @RonMaupin i guess that's a good idea. We've always used 15 and never had problems. Pretty straight forward to change a broken one too.
    – user36472
    Mar 1, 2019 at 17:50
  • Just wanted to add that we added the switch this morning. I did configure "switch 1 renumber 4" before adding the switch to the stack and it worked. But now I wonder if I had configured "switch 1 renumber 5" if it would have worked (4 was the first available number) - I'm not 100% convinced the command is taken into account.
    – user53632
    Mar 6, 2019 at 7:32

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