If a seed node is unavailable, you might experience service loss on an Avaya Aura® Web Gateway cluster. You will also be unavailable to install a new node on the cluster. To prevent this issue from occurring, you can specify a list of backup nodes for the seed node while performing silent installation. If the initial seed node becomes unavailable, Cassandra replaces it with a node from the backup nodes list, so the cluster continues to operate. When you add a new node, Cassandra checks whether the initial seed node is available. If not, Cassandra tries to connect the new node to one of backup nodes.

Specify backup nodes in the SEED_NODE_BACKUP property of the installation.properties file. The value of this parameter is a list of IP addresses separated by commas. For example: SEED_NODE_BACKUP=192.168.150.3,192.168.150.4. If the seed node is unavailable, Cassandra tries to replace it with a node listed in SEED_NODE_BACKUP in the order specified in the property. On Avaya Aura® Web Gateway, you can review the seed nodes configuration in the /opt/Avaya/CallSignallingAgent/<version>/cassandra/<version>/conf/cassandra.yaml file.