We have 2 firewall clusters consisting of fortigate 300C models with internal interface on both to the same local network (184.108.40.206/24). Each cluster has dedicated connections for clustering control lines.
Cluster 1 interface IP: 220.127.116.11/24
Cluster 2 interface IP: 18.104.22.168/24
This internal IP address is used to as well manage the firewall.
When both clusters are UP then only Cluster 2 interface is not stable. Ping frequently times out to cluster 2 IP. When Cluster 1 is shutdown then Cluster 2 has no issue. Behaviour is as if there was an IP conflict but there is none.
Cluster 2 was loaded by taking the configurations backups from Cluster 1 and modifying some parameters such as interface IPs.
Any idea why this setup does not work or any hints what to check? There are no IP conflicts in the design.