Active-Standby configuration - more than 2 devices?

Adding a 3rd device will require additinal self IPs, additional firewall permissions to allow monitoring from the new self IPs to the pool members.

Here is the plan:

Replace machine A by machine C.

Replace machine B by machine D.

Prepare C and D with the network settings (VLAN and Self IPs) of the corresponding machines A and B.

Put C and D in "Forced Offline" mode.

That´s why I prefer to do the following:

1. Backup both machines (active [A] and standby [B])
2. Put machine B into "Forced Offline" mode and isolate it from the network
3. Remove machine B from the sync-failover device group and delete the device trust
4. Add machine D (having the network settings of machine B) to your network
5. Establish device trust from A to D, add D to the sync failover group, do the initial sync from A to D
6. Release D from "Forced Offline" and watch the monitoring results
7. If everything becomes "green" on machine D and Self IPs are reachable, trigger a failover
8. If everything runs fine through D now, you can apply the same procedure to replace A by C.

I have done this a couple of times with both v14 and 15 and faced no issues so far.