Looking to add a second ftd in fmc. This second ftd was previously replaced by the existing ftd. The older ftd has a different management ip address which should be fine however the data interfaces still have the same ip addresses. I am wanting to confirm that it should not be an issue as long as the data interfaces are not online at the time of adding the device with the intention of changing the data interfaces ip addresses once it has been successfully re-added. Please advise.
Is this part of the HA you are replacing with a new one?
Yes, adding the second Firepower Threat Defense (FTD) to your Firepower Management Center (FMC) with overlapping data interface IP addresses is generally safe, provided the data interfaces are disconnected or in a "shutdown" state to prevent network-level IP conflicts (ARP/routing issues)
OLD guide still steps valid, make sure new FTD correct stable version and FMC can manage.
https://www.cisco.com/c/en/us/support/docs/security/firepower-ngfw/200701-Configuration-of-Management-access-to-FT.html
