Hello Martin
You can add, delete, or reorder sequence numbers in a route-map without impacting the current state by using the sequence numbers that Cisco IOS allocates to individual statements within a route-map. By default, Cisco IOS assigns sequence numbers in increments of 10, so you can insert new statements between existing ones without having to redo the entire configuration.
To add a sequence, you simply specify a new number with the route-map command. For example, if you have sequences 10 and 20, you can add sequence 15 with the command route-map MAP_NAME permit 15.
To delete a sequence, use the no form of the route-map command, like no route-map MAP_NAME permit 10.
To reorder, you’ll have to remove and re-add the sequences in the order you want them. This can be a bit disruptive but if you prepare the commands beforehand, you can paste them in quickly to minimize the impact.
Remember, changes to route-maps take effect immediately as you enter them. So, it’s a good idea to make these changes during a maintenance window if possible.
As for your VM router running Version 12.4(24)T8, you should be able to manipulate sequence numbers. If you can’t, it might be a bug or limitation of the virtual platform you’re using.
To minimize impact, changes on production networks are generally made during scheduled maintenance windows and are thoroughly tested in a lab environment before being implemented in a live network. Thus possible mistakes are caught beforehand, and the impact on the network is minimized.
I hope this has been helpful!
Laz