In the dashboard go to:
Organization > Configure > Settings under Organization Settings select Name to change "ABC" to "123."
No impact to DNS, DHCP or other systems...just the name of the Organization.
You would need to update any API references if using APIs after making changes to the org name. And if using NMVPN you might want to double check your settings (if using NMVPN - IPSec VPN peers).
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