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It's good to start with a public seed node and try to keep it up and running.
To make your seed node available to general public you will need to add:
p2p-endpoint = 0.0.0.0:2001
and let people know on a steem.chat's #seed-nodes channel that a new seed-node is in town ;-)
Static IP is required and some reliable hostname is preferred.
(above is true for public seed node)