Dynomite supports 2 methods to maintain a node's membership status:

1-Centralized membership system

Each dynomite node will periodically reach out to a local service (a proxy to the centralized service) to obtain the cluster members. For more information, please look at this code: https://github.com/Netflix/dynomite/blob/master/src/seedsprovider/dyn_florida.c#L13

You can also check the token management section by Dynomite-manager.

2-Gossip

Gossip is disabled by default and can be turned on by providing "-g" flag on the command line. Each node maintains a data structure on the rest of the cluster topology and periodically pick a random node to spread out its data. Note that in using this you still need to provide a seed list for each node. https://www.cs.cornell.edu/~asdas/research/dsn02-swim.pdf