Renumbering Switches in a Stack

[InquiringTech]

OK, so I realized the switches in our stack are numbered wrong, with 1 and 2 backwards, and 3 being okay.

I wanted to do a "switch 1 renumber 2 command", and got a warning saying "Changing the switch number may result in a configuration change for that switch. The interface configuration associated with the old switch number will remain as a provisioned configuration. New Switch Number will be effective after next reboot. Do you want to continue?"

The part in bold confuses me a bit. Does that mean that even after a reload/reboot of the switch, it will keep the old interface configuration, despite the number change? Isn't the whole point of the renumber command to rename the ports like 1/0/1 to 2/0/1 and vice-versa? (because that's what I want to do). Or is this referring to something else, like specific configs on those interfaces?

Also, would I have to both do a "switch 1 renumber 2" and a "switch 2 renumber 1" command, or would they automatically switch numbers? From what I read, they don't and if there is a conflict in number they will take the lowest available number, if I'm not mistaken?

Thank you!

[Elliot Dierksen · Accepted solution]

I think you would have to do that in a 3 step process. "switch 1 renumber 4 command", then "switch 2 renumber 1 command", and last "switch 4 renumber 2 command". If everything else is already working, wouldn't it be a lot easier and less disruptive to to change the labels on the physical switches? You could also erase the config, power all the switches off, and then rebuild the stack powering 1 switch on at a time. I would lean towards just changing the physical labels on the switches. All the other options have some serious disaster potential.

[InquiringTech]

Yeah, I guess you're right. It's not worth it risking everything to just renumber a switch, so I slapped some new labels on them. There is no functional problem with the current setup, so if it ain't broke don't fix it.

[Tomáš Šupa]

No, this is not correct. Who wants to have stack members scattered in the rack? That's what an amateur does...
It is possible to do it together without any intermediate step of changing member 1 to member 4. 
The correct and proven steps are:
switch 1 renumber 2 
switch 2 renumber 1
reload

The port configuration remains the same => If port Gi1/0/1 was configured as a trunk, it will be a trunk after this change/reload.
You just have to change the priority of the switch after reload. If switch 1 had a priority of 15, after the restart and this change, switch 2 will have this priority, so you must change it with:
switch 1 priority 15
switch 2 priority 1
write

[pieterh]

I agree with Elliot it would be simpeler to change the labels

>>> Isn't the whole point of the renumber command to rename the ports like 1/0/1 to 2/0/1 and vice-versa? <<
yes this is correct but will only happen AFTER the reboot
if not yet rebooted, then both ports are "present" in the configuration (as if there are two members in the stack)
you can still reconfigure port 1 on this member using the old name 1/0/1 (running-config)
2/0/1 becomes the name of the same physical port AFTER the reboot (from startup-config)

[InquiringTech]

Ah, okay thanks for clearing that up.

By the way, in some of the relevant examples I've searched, I've seen people entering a "no provision .." command after the renumber. What exactly does that do?

[pieterh]

the members and its model are included in the switch's configuration
on a switch with two members, in the configuration you will find lines like:
     switch 1 provision ws-c3750-48p
     switch 2 provision ws-c3750-48p
on a single switch there is only one line,
on a renumbered switch an line is added (provisioned) in the configuration with the new assigned number,
the old number is also still present, still there is only one physical switch,
therefore, after the reboot you need to remove the line with the unused number with the commands
   configure terminal
      no switch 2 provision ws-c3750-48p
   end
   write   !(or copy running-configuration startup-configuration)

[CSCO11598534]

Has anyone tried that out (any of the two ways proposed above)?

Still, i wonder what is the way to flip the numbering, without needing to change each port configuration.

[pieterh]

it has been a while since I've actually done such a renumbering, so below procedure is from memory

afaik, if you just flip the switch-numbering, it will not go as you desire
e.g. with a stack of two switches switch-1 and a switch-2
when you renumber the switch , Gi2/0/1 cannot be renumbered to Gi1/0/1 because Gi1/0/1 already exists (v.v.)
as a result Gi1/0/1 and Gi2/0/1 have the same config as before renumbering

-> suggested procedure  to maintain the port-configuration:
    renumber switch-2 to switch-3 (or other free number) , remove switch-2 provisioning statement and reload
    after this reload Gi2/0/1 should be  renumbered to Gi3/0/1
    renumber switch-1 to switch-2 , remove switch-1 provisioning statement and reload
    renumber switch-3 to switch-1 , remove switch-3 provisioning statement and reload
==>> because of the multiple reloads this is not a very pleasant procedure

quicker (less downtime)  is to
- save your port config in a text file
- edit your text file to represent the renumbering and save to flash:port-config.txt
- default all your interfaces
(- you may also chose to shutdown to avoid connectivity issues, then also add "no shutdown" in your textfile)
- renumber switches and reload once 
- copy  flash:port-config.txt running-config
- save new config (write or "copy run start")

[clive.fulton]

the command "show switch" will show the switches and their current numbers.  Is there a command which lists what the switches WILL be after the next boot?