If you are using clustering in a network that uses firewalls, you should be aware of some limitations and requirements.
If you are using clustering with a firewall, you need to allow each node the ability to send outbound messages to and receive inbound messages from other cluster nodes. An opening in the firewall must exist for each cluster address on each node to communicate with every cluster address on every other node. IP packets traveling across a network can be of various types of traffic. Clustering uses ping, which is type ICMP, and also uses UDP and TCP. When a user configures a firewall, they can filter traffic based on the type. For clustering to work the firewall needs to allow traffic of ICMP, UDP and TCP. Outbound traffic can be sent on any port and inbound traffic is received on ports 5550 and 5551.
