FMC, FTD

[Dkiptoo]

I have an FMC 4600 managing two(2)  FTD 4145 instances. The two instances were working fine and manageable from the fmc. For some unknown reason, one instance disappeared.   All policies are pushed from the FMC . At now I cannot see the instance on the managed devices on FMC.  Both instances are up and running. How can I bring back the instance. Re registering without losing the configs

[Dkiptoo]

A follow up on this, from the ftd instances, when I show managers, it displays as registration pending 

[Marius Gunnerud]

I have had this happen to me.  The devices were removed from Devices in the FMC.  I had a TAC case on it and the only way to get them back is to onboard them again to the FMC.  Sorry for the bad news.

[Dkiptoo]

Will onboarding again mean losing the previous configurations?  This this because policies were pushed from the FMC 

[Marius Gunnerud]

When onboarding the configuration on the devices will be reset.  The only configuration that will be fetched or maintained are the interface configuration.  All other configuration will need to be added back.  Now, keep in mind this means that you will need to associate the ACP policy, NAT policy again as they are not deleted from FMC but are no longer associated with the FTD, so it is just a matter of adding it back.

You will also need to associate the interfaces with their respective security zones, configure routing, and any VPN configuration (site to site and remote access VPN).

When this happened to me it was several remote sites that fell out.  after this I started to connect the FTDs to FMC via the data interface as it was a pain to get someone onsite to these locations to provide console access.