How grid nodes discover the primary Admin Node

After a grid node is deployed, it must know how to connect to the grid’s primary Admin Node for configuration and management.

To connect to the primary Admin Node, each grid node uses the primary Admin Node’s IP address for the Grid Network. When you enter the settings used for deployment, you use the ADMIN_IP setting to provide this value manually.

Grid nodes can also automatically discover the primary Admin Node’s IP address. Automatic discovery of the primary Admin Node is accomplished using a multicast Domain Name System (mDNS). When the primary Admin Node first starts up, it publishes its IP address using mDNS. Other nodes on the same subnet can then query for the IP address and acquire it automatically. However, because multicast IP traffic is not normally routable across subnets, nodes on other subnets cannot acquire the primary Admin Node’s IP address directly.

For this reason, you must include the ADMIN_IP setting for at least one grid node on any subnets that the primary Admin Node is not directly attached to. This grid node can then publish the primary Admin Node’s IP address for other nodes on the subnet to discover.