Reseed

Reseeding is the way an I2P router bootstraps itself into the I2P network by getting information about other I2P nodes to connect to them.

In short: When started for the first time, or when it runs out of known peers, I2P tries to fetch a "reseed file" from a HTTPS host (in a fixed list of hosts) via Clearnet, which contains information for around 100 peers (randomly taken from a live netDB). After the file is fetched and checked against a valid certificate (from a fixed list of certs), the netDB entries within the reseed file are saved and I2P will start trying to connect to these peers to bootstrap itself into the I2P network.

HowTo run a reseed server

You can see how to setup a reseed server on I2P's project website (In-Network or Clearnet)