https://community.cisco.com/t5/network-security/second-ftd-in-fmc/m-p/5372770#M1124573 <P>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.</P><P>TIA!</P> Wed, 25 Feb 2026 22:48:42 GMT san.carlos 2026-02-25T22:48:42Z https://community.cisco.com/t5/network-security/second-ftd-in-fmc/m-p/5372770#M1124573 <P>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.</P><P>TIA!</P> Wed, 25 Feb 2026 22:48:42 GMT https://community.cisco.com/t5/network-security/second-ftd-in-fmc/m-p/5372770#M1124573 san.carlos 2026-02-25T22:48:42Z https://community.cisco.com/t5/network-security/second-ftd-in-fmc/m-p/5372777#M1124574 <LI-CODE lang="markup">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.</LI-CODE> <P>Is this part of the HA you are replacing with a new one?</P> <P>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)</P> <P>OLD guide still steps valid, make sure new FTD correct stable version and FMC can manage.</P> <P><A href="https://www.cisco.com/c/en/us/support/docs/security/firepower-ngfw/200701-Configuration-of-Management-access-to-FT.html" target="_blank">https://www.cisco.com/c/en/us/support/docs/security/firepower-ngfw/200701-Configuration-of-Management-access-to-FT.html</A></P> Wed, 25 Feb 2026 23:13:27 GMT https://community.cisco.com/t5/network-security/second-ftd-in-fmc/m-p/5372777#M1124574 balaji.bandi 2026-02-25T23:13:27Z https://community.cisco.com/t5/network-security/second-ftd-in-fmc/m-p/5372810#M1124575 <P>Thanks for your response. It is not an HA setup and not yet looking to go HA, just register the device for now. Thanks for confirming should be no issue adding the device provided the data interfaces are offline. Yes, I have confirmed FMC can manage FTD.</P> Thu, 26 Feb 2026 02:15:00 GMT https://community.cisco.com/t5/network-security/second-ftd-in-fmc/m-p/5372810#M1124575 san.carlos 2026-02-26T02:15:00Z